JPH07168719A - Redundant type removing device - Google Patents

Abstract

PURPOSE:To remove an operation expression to be redundant by comparing cost before and after the reload of a program and reloading arithmetic in the program later. CONSTITUTION:A cost extracting part 7 retrieves a cost storage part 5 and extracts the cost, and first, second and third reloading cost extracting parts 8, 9 and 10 reload an element to be calculated by arithmetic, retrieve a cost storage part 5 and an addressing cost storage part 6 with the reloaded arithmetic and extract the cost of arithmetic. A comparison part 11 compares the extracted cost. When the cost extracted by the first, second and third reloading cost extracting parts 8, 9 and 10 is smaller as the result of comparison, reloading is performed, and the redundant operation expression is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a redundant expression removing device which is provided in a compiler for translating a source program written in a high-level language into a machine language program and removes redundant arithmetic expressions from a program to be processed. .

[0002]

2. Description of the Related Art In recent years, programs have been written in a high-level language such as C language to improve program development efficiency. Source programs written in these high-level languages are translated into machine language programs that can be understood by a computer by using various compilers.

The compiler shortens the execution time of the machine language program finally created and reduces the memory size (execution time of the machine language program finally created, or the memory size collectively The source program created by the programmer, or the intermediate language program created by the compiler to perform internal processing is subjected to various processing. One of the methods of reducing the cost in this way is to delete redundant arithmetic expressions from the program. In order to delete such a redundant arithmetic expression (this arithmetic expression is referred to as a redundant expression), the conventional compiler is equipped with a redundant expression removing device that removes the redundant expression by various deleting methods. Before describing the redundant removal device, the terms used are defined below. -Operation This refers to the code of a program composed of variables, constants, and operators, such as 100 * x + 2 and x / 200 + y. Calculation formula For example, y = 130, y = 100 * x + 2, y = x / 2
This is an expression in which a variable exists on the left side of the equal sign and an operation exists on the right side, such as 00 + 10. Definition of variables The contents of variables are set by calculation, for example, a = b + c, s = 100 * 2. -Use of variables The use of variables as operands of operations. -Stack variable A variable that is placed on the memory of the stack area. -Static variable A variable that is placed on the memory at a specific address outside the stack area. -Register variables These are variables placed on registers. First, a redundant type elimination device for eliminating common sub-expressions will be described. Deletion of a common subexpression means a process in which, when a plurality of operations for performing the same operation are present in a program, only one of them is left and all others are deleted. FIG. 10 is a block diagram of a redundant type removal device that deletes a common sub-expression.

A redundant expression removing device for deleting common sub-expressions (device for deleting common sub-expressions in the figure) is a calculation appearance place detecting section 22, a result use place detecting section 23, and an operator rewriting section. 24, an arithmetic expression removing unit 25, and a processing target holding unit 26. The operation appearance location detection unit 22 detects all the operations whose operands are exactly the same from the programs stored in the processing target storage unit 26. In particular,
The operation appearance location detection unit 22 compares the operators and operands of all operations in the program held in the processing target holding unit 26 (if the operand is a variable, the contents of the variable are It is used for comparison.), And all operations whose operands are the same are detected. After the detection, the operation appearance place detection unit 22 notifies the arithmetic expression removal unit 25 of the position of the arithmetic expression whose operation exists on the right side of the equal sign (this arithmetic expression is referred to as a common subexpression). Also, variables defined by the detected operation are detected, and among these variables, the variable located first (this variable is referred to as the designated variable) is the operand rewriting unit 24.
And outputs the second and subsequent variables (these variables are called deletion variables) to the result use place detection unit 23.

The result use place detection unit 23 receives the deletion variable from the operation appearance place detection unit 22, and the deletion variable is
An operation used as an operand (this operation is called a rewriting arithmetic expression) is detected, and the detected position is notified to the operator rewriting unit 24. The operand rewriting unit 24 receives the designated variable from the operation appearance location detection unit 22 and designates the deletion variable used as the operand in the rewriting arithmetic expression of the position notified from the result use location detection unit 23. Rewrite as a variable.

The arithmetic expression removing section 25 deletes the arithmetic expression at the position notified from the arithmetic appearance location detecting section 22. The processing target holding unit 26 holds a program to be processed.
The program to be held may be written in the source code written by the programmer or may be written in the internal code generated by the compiler for the convenience of internal processing.

The redundant type elimination device configured as described above for eliminating common sub-expressions removes common sub-expressions from a program as shown in FIG. First, the calculation appearance location detection unit 22 detects the calculation indicated by the arrows a1, a2, and a3. Next, the result use place detection unit 23 detects the operation (the operation shown by the arrows b1 and b2 in the figure) in which the deletion variables x1 and y1 are used as the operands. After detection,
The operand rewriting unit 24 replaces the operands of the operations of the arrows b1 and b2 with the designated variable x as indicated by the arrows c1 and c2 of FIG.
Rewrite As a result, this program is rewritten as shown in FIG.

Secondly, a redundant type elimination device for propagating a value will be described. In value propagation, the variable used as an operand in an operation is rewritten as a variable or constant with the same value, and the arithmetic expression of the variable used as the operand is deleted from the program. It is to be. FIG. 13 is a block diagram of a redundant removal device that propagates a value.

The redundant type elimination device (propagation device for propagating values in the figure) for propagating a value has a substitution appearance place detecting section 32, a result using place detecting section 33, an operand rewriting section 34,
The substitution removing unit 35 and the processing target holding unit 36 are included. The substitution appearance location detection unit 32 detects all arithmetic expressions for substituting variables for constants or arithmetic expressions for substituting variables for variables from the program stored in the processing target storage unit 36, and determines the position of the arithmetic expression. , The substitution removing unit 35 is notified.
Further, a variable defined by the detected arithmetic expression (this variable is also called a deletion variable) is detected and output to the operand rewriting unit 34. Further, in the above arithmetic expression, variables and constants existing on the right side of the equal sign (these are called designated substitution numbers).
Is output to the operator rewriting unit 34.

The result use place detection unit 33 receives the deletion variable from the substitution appearance place detection unit 32, and performs an operation in which the deletion variable is used as an operand (this operation is called a rewriting operation expression). Then, the detected position is notified to the operator rewriting unit 34. The operand rewriting unit 34 receives the designated number of substitutions from the substitution appearance place detection unit 32, and in the rewriting arithmetic expression of the position notified from the result use place detection unit 33, deletes the deletion variable used as the operand, Rewrite to the specified substitution number.

The substitution removing unit 35 is a result use place detecting unit 3
The arithmetic expression of the position notified from 3 is deleted. The processing target holding unit 36 holds the program to be processed, similar to the processing target holding unit 26. The redundant removal device configured to propagate the value configured as described above propagates the value to the program as shown in FIG. First, the substitution appearance place detection unit 32 detects the arithmetic expression shown by the arrow d1, and then the result use place detection unit 33 detects the calculation shown by the arrows e1 and e2. After the detection, the operand rewriting unit 24 displays the arrow e
The operands of the operations 1 and e2 are represented by the arrows f1 and f2 in FIG.
The designated substitution number 4000 is rewritten as follows. as a result,
This program is rewritten as shown in FIG.

[0012]

However, according to the above-mentioned prior art, in the redundant expression elimination device that deletes common sub-expressions and propagates values, the operands of the operations to be processed are
Since the operand is rewritten without checking whether it corresponds to a constant, a register variable, a stack variable, or a static variable, there is a problem that the rewriting may increase the cost. It was

Further, the processor of the target machine is
When addressing modes such as indirect address reference with index and offset, indirect address reference with offset, etc. can be used, the compiler cannot rewrite operations that can effectively use these addressing modes. There is a problem that the cost cannot be reduced sufficiently.

For example, in the programs shown in FIGS. 11 and 14, it is assumed that the variable x is a stack variable placed in the stack area and the variables x1 and y1 are register variables placed in a register. Generally, the stack variable needs to access the memory in the stack area, and is more expensive than the register variable. Therefore, if the operation in which the register variables x1 and y1 are used is rewritten to the stack variable x,
Rewriting may increase the cost of the entire program. In addition, in a machine language instruction, for an operation that uses a constant value of 16 bits or more as an operand, it is necessary to describe the operand in the operand of the machine language instruction.
It is often more expensive than operations that use memory as the operand. Therefore, when the variable x in FIG. 7 is rewritten to a constant value of 16 bits or more, the rewriting may increase the cost of the entire program.

Further, FIG. 16A shows a part of a program in which address calculation is described by using pointer variables of C language, and FIG. 16B shows a result of resource allocation of these variables. is there. The processor of the target machine is a two-operand type processor.
Address register indirect reference as shown in (c) can also be performed. Even in such a situation that the addressing mode can be used, the rewriting performed by the compiler is the rewriting for the 2-operand format processor.
The operation cannot be rewritten so as to correspond to the machine language instruction in the addressing mode of (c). Therefore, the compiler cannot use the machine language instruction for performing such address register indirect reference in the process of translating the machine language program, and the cost of the program increases accordingly.

In view of the above problems, the present invention judges whether or not rewriting is effective before rewriting the operand of an operation, and if the rewriting is effective, rewrites the operand, An object of the present invention is to provide a redundant expression removing device that removes unnecessary arithmetic expressions by rewriting and further rewrites operations so that the addressing mode is effectively used.

[0017]

In order to solve the above-mentioned problems, the redundant type elimination device of the present invention is provided in a compiler,
A redundant expression removing device that rewrites the operation of a program held in the program holding means and removes a redundant arithmetic expression after rewriting, in which an operator and an operand are the same operation from the program of the program holding means. Detect all, detect all variables defined by the operation,
The operation detecting means for storing the position of the operation expression including the detected operation and the variable, and the variables located after the second among the variables detected by the operation detecting means detect all the operations used as the operands. Cost detecting means for storing the operand detection means, the type of the arithmetic expression, and the cost of the arithmetic expression corresponding to these types, and the type of the arithmetic expression detected by the operand detecting means The first cost extraction means for extracting the cost corresponding to the type of the arithmetic expression by the cost storage means and the operand of the arithmetic expression detected by the operand detection means and the variable detected by the operation detection means. Second, the cost storage unit is searched for the type of the arithmetic expression when the variable located first is used to retrieve the cost corresponding to the type of the arithmetic expression.
Of the cost take-out means, the cost taken out by the first cost take-out means, and the cost taken out by the second cost take-out means, and the result of the comparison means comparing, the second cost take-out means is If the cost of taking out is small,
Rewriting means for rewriting the position in the program of the variable used as the operand to the variable detected first by the operation detecting means by the operation detected by the operator detecting means, and detected by the operator detecting means When the rewriting means rewrites all the variables under operation, the operation expression including the variable used as the operand in the operation detected by the operand detecting means and the operation in which the variable was defined To
And removing means for removing from the program.

The first cost take-out means obtains the total sum of the taken-out costs, the second cost take-out means obtains the total sum of the taken-out costs, and the comparison means obtains the first cost take-out means. The total sum of the costs may be compared with the total sum of the costs obtained by the second cost extraction means. Also,
The comparison means may compare the individual cost extracted by the first cost extraction means with the individual cost extracted by the second cost extraction means.

Further, the redundancy removing apparatus is provided in the compiler and rewrites the operation of the program held in the program holding means, and removes redundant arithmetic expressions after the rewriting. Operation detecting means for detecting all operations having the same child and operand, detecting all variables defined by the operations, and storing the position of the operation expression including the detected operation and the variables; Among the variables detected by the detection means, the second and subsequent variables are the operand detection means for detecting all the operations used as the operands, the type of the arithmetic expression, and the type of the arithmetic expression. The cost storage means for storing the cost of the arithmetic expression corresponding to the type and the cost storage means for the type of the arithmetic expression detected by the operand detection means are searched for the cost corresponding to the type of the arithmetic expression. The cost storage means is searched for with an arithmetic expression type of an arithmetic expression including a first cost extracting means to be issued and an arithmetic operation positioned after the first operation among the operations detected by the operation detecting means, and the type of the arithmetic expression is obtained. A calculating means for obtaining the sum of the costs taken out by the redundant type cost taking means for taking out the corresponding costs and the first cost taking means and the costs taken out by the redundant type cost taking means, and the arithmetic expression detected by the operand detection means The cost storage means is searched for by the type of the arithmetic expression when the variable located first among the variables detected by the arithmetic detection means is used as the operand of, and the cost corresponding to the type of the arithmetic expression is extracted. As a result of comparison between the comparison means and the comparison means for comparing the sum of the costs obtained by the second cost extraction means and the calculation means with the costs extracted by the second cost extraction means, the second cost extraction means extracts the costs. If the cost is small, the rewriting means for rewriting the position in the program of the variable used as the operand by the operation detected by the operand detecting means to the variable detected first by the operation detecting means; When the rewriting means rewrites all the variables in the operation detected by the operator detecting means, the variable used as the operand in the operation detected by the operand detecting means and the variable are defined. An arithmetic expression that includes and
A removing means for removing from the program may be provided.

Further, the first cost take-out means obtains the sum of the taken out costs, and the calculating means takes the sum of the costs taken out by the first cost taking means and the cost taken out by the redundant type cost take-out means. The second cost extraction means calculates the sum, and the comparison means calculates the sum of the extracted costs.
You may make it compare the sum of the cost calculated | required by the calculation means, and the sum total of the cost calculated | required by the 2nd cost extraction means.

The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the cost taken out by the redundant cost taking means, and the comparing means gives the sum of the costs obtained by the calculating means. And the individual costs obtained by the second cost extraction means may be compared. In addition, a redundant removal device that is provided in the compiler, rewrites the operation of the program held in the program holding means, and removes a redundant arithmetic expression after the rewriting. , An arithmetic expression for substituting a constant for a variable, and an arithmetic expression detecting means for detecting all arithmetic expressions for substituting the value of a variable for a variable, and a variable existing on the left side of the equal sign of the arithmetic expression detected by the arithmetic expression detecting means. Stores the operand detection means for detecting all the arithmetic expressions used as operands from the program holding means, the type of the arithmetic expression, and the cost of the arithmetic expression whose arithmetic expression type corresponds to these types. First cost extraction means for extracting the cost corresponding to the type of the arithmetic expression by searching the cost storage means with the type of the arithmetic expression detected by the operand detection means, and the operand The cost storage means is searched with the type of the arithmetic expression when the variable located first in the variables detected by the arithmetic expression detecting means is used as the operand of the arithmetic expression detected by the outputting means, Second cost extraction means for extracting the cost corresponding to the mold, comparison means for comparing the cost extracted by the first cost extraction means with the cost extracted by the second cost extraction means, and the first cost extraction If the cost extracted by the means and the cost detected by the second cost extracting means are compared with each other by the comparing means, and if the cost extracted by the second cost extracting means is small, the operand detection is performed. Rewriting means for rewriting the position in the program of the variable used as the operand in the operation detected by the means to the variable or constant detected by the operation expression detecting means,
When the rewriting means rewrites all variables in the operation detected by the operand detection means, the variable used as the operand in the operation detected by the operand detection means exists on the left side of the equal sign. And a removal unit that removes from the program an arithmetic expression that is an arithmetic expression and that is detected by the arithmetic expression detection unit.

Further, the first cost take-out means obtains the total sum of the taken out costs, the second cost take-out means obtains the total sum of the taken out costs, and the comparison means obtains the first cost take-out means. The total sum of the costs may be compared with the total sum of the costs obtained by the second cost extraction means. Further, the comparing means may compare the individual cost extracted by the first cost extracting means with the individual cost extracted by the second cost extracting means.

Further, the redundant type removing device is provided in the compiler and rewrites the operation of the program held in the program holding means and removes the redundant arithmetic expression after the rewriting, and is held in the program holding means. To the left side of the equal sign of the arithmetic expression detected by the arithmetic expression detection means and the arithmetic expression that substitutes the value of the variable into the variable Operand detection means for detecting all operation expressions used as operands from the program holding means, existing operation types, operation expression types, and operation expression costs where the operation expression types correspond to these types A cost storage means for storing and a cost storage means for searching the cost storage means by the type of the arithmetic expression detected by the operand detection means, and extracting a cost corresponding to the type of the arithmetic expression
Redundant cost take-out means and first cost take-out means for searching the cost storage means with the type of the arithmetic expression of the arithmetic expression detected by the arithmetic expression detecting means and taking out the cost corresponding to the type of the arithmetic expression The cost extracted by the means and the calculation means for obtaining the sum of the costs extracted by the redundant cost extraction means and the operand of the arithmetic expression detected by the operand detection means,
Second cost extraction means for searching the cost storage means with the type of the arithmetic expression when the variable located first in the variables detected by the arithmetic expression detection means is used and for extracting the cost corresponding to the type of the arithmetic expression And the comparison means for comparing the sum of the costs calculated by the calculation means and the costs extracted by the second cost extraction means, and the comparison means, if the cost extracted by the second cost extraction means is small, Rewriting means for rewriting the position in the program of the variable used as the operand in the operation detected by the operand detection means to the variable or constant detected by the arithmetic expression detection means and the operand detection means detected When the rewriting means rewrites all the variables in the calculation, the variable used as the operand in the calculation detected by the operand detecting means is an arithmetic expression on the left side of the equal sign. And, the redundant expression removing device characterized by comprising a removing means for removing the arithmetic expression detected by the arithmetic expression detecting means from the program, and the first cost extracting means obtains the total of the extracted costs, The calculation means calculates the sum of the costs extracted by the first cost acquisition means,
The second cost extracting means obtains the sum of the extracted costs, the second cost extracting means obtains the total of the extracted costs, and the comparing means obtains the sum of the costs obtained by the calculating means and the second cost. You may make it compare with the sum total of the cost which the extraction means calculated.

The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the cost taken out by the redundant cost taking means, and the comparing means gives the sum of the costs obtained by the calculating means. And the individual costs obtained by the second cost extraction means may be compared. Further, it is a redundant type removing device which is provided in the compiler, rewrites the operation of the program held in the program holding means, and removes a redundant arithmetic expression after the rewriting, and is a pointer from the program of the program holding means. An operation detecting unit that detects an operation expression in which a variable is defined and stores the detected operation and the position of the operation expression including the variable, and an operation in which the variable detected by the operation detecting unit is used as an operand. Operand detecting means for detecting all expressions, and an arithmetic expression that can be executed by one machine language instruction, and is used as an operand used for a pointer, an operand used for an index, and an offset Of the operands that are
The cost storage means is searched by a cost storage means for storing the type of the one including at least two operands, the cost of the arithmetic expression corresponding to the type of the arithmetic expression, and the arithmetic expression detected by the operand detection means. When the operation detected by the operation detecting means is applied to the first cost extracting means for extracting the cost of the arithmetic expression corresponding to the arithmetic expression and the operand of the arithmetic expression detected by the operand detecting means The second cost extraction means for searching the cost storage means and extracting the cost corresponding to the calculation expression by the type of the arithmetic expression, the cost extracted by the first cost extraction means, and the second cost extraction means If the cost extracted by the second cost extraction means is small as a result of comparison by the comparison means for comparing the extracted cost with the comparison means, it is used as the operand in the arithmetic expression detected by the operand detection means. Rewriting means for rewriting the position of the variable in the program to the operation detected by the operation detecting means, and when the rewriting means rewrites the variables in all the arithmetic expressions detected by the operand detection means, the operation detecting means And a removing unit that removes the arithmetic expression including the arithmetic operation detected by the program.

Further, the first cost take-out means obtains the total sum of the taken-out costs, the second cost take-out means obtains the total sum of the taken-out costs, and the comparison means obtains the first cost take-out means. The total sum of the costs may be compared with the total sum of the costs obtained by the second cost extraction means. Further, the comparing means may compare the individual cost extracted by the first cost extracting means with the individual cost extracted by the second cost extracting means.

Further, the redundancy removing apparatus is provided in the compiler and rewrites the operation of the program held in the program holding means, and removes the redundant arithmetic expression after the rewriting. An operation detection unit that detects an operation expression that defines a variable that is a pointer and stores the detected operation and the position of the operation expression that includes the variable, and the variable that the operation detection unit detects are used as operands. Operator detecting means for detecting all the arithmetic expressions that are present, an arithmetic expression that is an arithmetic expression that can be executed by one machine language instruction, and that is used as a pointer, an operand that is used as an index, and Of the operands used for the offset, a type that stores at least two operands and a cost of the arithmetic expression corresponding to the type of the arithmetic expression The first cost extraction means for extracting the cost of the arithmetic expression corresponding to the arithmetic expression by the cost storage means and the arithmetic expression detected by the operand detection means, and the operation detection means Redundant type cost extraction means for searching the cost storage means with an operation expression type of an operation expression including an operation positioned after the second operation and extracting a cost corresponding to the operation expression type and the first cost Among the variables detected by the operation detection means, the operand of the arithmetic expression detected by the calculation means and the operand detection means for obtaining the sum of the cost extracted by the extraction means and the cost extracted by the redundant type cost extraction means The sum of the cost obtained by the second cost extraction means that retrieves the cost corresponding to the type of the arithmetic expression by searching the cost storage means with the type of the arithmetic expression when the variable located first is used, and the cost calculated by the calculation means. When As a result of comparison between the comparison means and the comparison means for comparing the cost extracted by the second cost extraction means, if the cost extracted by the second cost extraction means is small, the arithmetic expression detected by the operand detection means Rewriting means for rewriting the position of the variable used as the operand in the program to the operation detected by the operation detecting means, and rewriting means for rewriting the variables in all arithmetic expressions detected by the operand detecting means In this case, the arithmetic expression including the arithmetic operation detected by the arithmetic operation detecting means may be removed from the program.

Further, the first cost take-out means obtains the total sum of the taken out costs, and the calculation means takes the sum of the costs taken out by the first cost take-out means and the cost taken out by the redundant type cost take-out means. The second cost extraction means calculates the sum, and the comparison means calculates the sum of the extracted costs.
You may make it compare the sum of the cost calculated | required by the calculation means, and the sum total of the cost calculated | required by the 2nd cost extraction means.

The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the cost taken out by the redundant cost taking means, and the comparing means gives the sum of the costs obtained by the calculating means. And the individual costs obtained by the second cost extraction means may be compared. Further, the cost stored in the cost storage means may be the execution time and / or the memory size of the machine language instruction corresponding to the type of the arithmetic expression.

[0029]

With the above-mentioned means, in the redundant type elimination apparatus of the present invention, the operation detecting means operates for the program of the program holding means, and all the operations having the same operator and operand are detected. All the defined variables are detected, and the position of the arithmetic expression including the detected operation and the variable is stored. Among the variables detected by the calculation detecting means, the operand detecting means operates for the second and subsequent variables, and all the operations used as the operands are detected. The cost storage means stores the types of the arithmetic expressions and the costs of the arithmetic expressions corresponding to these types of arithmetic expressions, and the first cost extraction means operates the cost storage means for the operands. The type of the arithmetic expression detected by the child detection means is searched, and the cost corresponding to the type of the arithmetic expression is extracted. Further, with respect to the cost storage means, the variable located first in the variables detected by the operation detecting means is used as the operand of the arithmetic expression detected by the operand detecting means by the second cost extracting means. In this case, a search is performed with the type of the arithmetic expression, and the cost corresponding to the type of the arithmetic expression is extracted. After taking out, the comparison means compares the cost taken out by the first cost taking means with the cost taken out by the second cost taking means. As a result of comparison by the comparison means, if the cost taken out by the second cost extraction means is small, the position in the program of the variable used as the operand in the operation detected by the operand detection means is rewritten by the rewriting means. By this, the calculation detecting means is rewritten to the first detected variable. When the rewriting means rewrites all variables in the operation detected by the operand detecting means, the variables used as the operand in the operation detected by the operand detecting means and the variables are defined. The arithmetic expression including the calculated arithmetic operation is removed from the program by the removing unit.

Further, in the redundant type elimination apparatus of the present invention by the above means, the arithmetic expression detecting means, by the arithmetic expression detecting means, substitutes a constant into the variable from the program held in the program holding means, and the value of the variable in the variable. All arithmetic expressions substituting for are detected. The operator detecting means detects, from the program holding means, all the arithmetic expressions used as operands of the variables existing on the left side of the equal sign of the arithmetic expression detected by the arithmetic expression detecting means. The cost storage means stores the types of the arithmetic expressions and the costs of the arithmetic expressions corresponding to the types of the arithmetic expressions, and the arithmetic expressions detected by the operand detecting means by the first cost extracting means. The cost storage means is searched with the type of, and the cost corresponding to the type of the arithmetic expression is retrieved. In the type of the arithmetic expression when the second cost extracting means uses the variable located first in the variables detected by the arithmetic expression detecting means as the operand of the arithmetic expression detected by the operand detecting means. Search the cost storage means,
The cost corresponding to the type of the arithmetic expression is retrieved. First
The cost taken out by the cost take-out means and the cost taken out by the second cost take-out means are compared by the comparison means, and as a result of the comparison means comparing, if the cost taken out by the second cost take-out means is small, The position in the program of the variable used as the operand in the operation detected by the operator detecting means is rewritten by the rewriting means to the variable or constant detected by the arithmetic expression detecting means. When the rewriting means rewrites all variables in the operation detected by the operand detection means, the variable used as the operand in the operation detected by the operand detection means exists on the left side of the equal sign. The arithmetic expression which is an arithmetic expression and which is detected by the arithmetic expression detecting means is removed from the program by the removing means.

Further, in the redundant type elimination apparatus of the present invention by the above means, the operation detecting means detects the operation expression in which the variable which is the pointer is defined from the program of the program holding means, and the detected operation and variable are detected. The position of the included arithmetic expression is stored. The variable detected by the operation detection means is the operation expression used as the operand,
All are detected by the operand detection means. The cost storage means is an arithmetic expression that can be executed by one machine language instruction, and includes operands used for pointers, operands used for indexes, and operands used for offsets. Of these, the type of the one including at least two operands and the cost of the arithmetic expression corresponding to the type of the arithmetic expression are stored. An arithmetic expression detected by the operand detection means,
The first cost extraction unit searches the storage unit and extracts the cost of the arithmetic expression corresponding to the arithmetic expression. The second cost extraction means searches the cost storage means with the type of the arithmetic expression when the arithmetic operation detected by the arithmetic operation detection means is applied to the operand of the arithmetic expression detected by the operand detection means, The cost corresponding to the arithmetic expression is retrieved. The comparison means compares the cost extracted by the first cost extraction means with the cost extracted by the second cost extraction means. As a result of comparison by the comparison means, the second
If the cost taken out by the cost extracting means is small, the rewriting means detects the position in the program of the variable used as the operand by the operation detecting means by the arithmetic expression detected by the operand detecting means. Can be rewritten as arithmetic. When the rewriting means rewrites the variables in all the arithmetic expressions detected by the operand detecting means, the arithmetic expressions including the arithmetic operations detected by the arithmetic detecting means are removed from the program by the removing means.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A redundant type removing apparatus according to an embodiment of the present invention will be described. This redundant removal device, like C language,
It is equipped with a high-level language compiler that can describe address calculation using variables. The compiler performs lexical analysis, syntactic analysis, and semantic analysis of the source program, and the contents of each variable are the respective operations in the program. Fired after the value of the expression is parsed. The program to be processed is an intermediate language program that the compiler outputs as an analysis result after performing lexical analysis, syntactic analysis, and semantic analysis. The structure of this redundant removal device is shown in FIG.

The redundant type elimination device 10 includes a control unit 1, a calculation generation position detection unit 3, a value use position detection unit 4, a cost storage unit 5, an addressing cost storage unit 6, a cost extraction unit 7,
1st rewriting cost extraction part 8, 2nd rewriting cost extraction part 9, 3rd rewriting cost extraction part 10, comparison part 1
1, the first rewriting unit 12, the first arithmetic expression removing unit 13,
Second rewriting unit 14, second arithmetic expression removing unit 15, third
Rewriting unit 16, third arithmetic expression removing unit 17, and processing target holding unit 18.

The control unit 1 includes a calculation generation position detecting unit 3, a value use position detecting unit 4, a cost extracting unit 7, a first rewriting cost extracting unit 8, a second rewriting cost extracting unit 9, and a third rewriting cost. The extraction unit 10 and the comparison unit 11 are activated in sequence.
The calculation generation position detector 3 includes a calculation appearance position detector 3a,
Substitution appearance position detector 3b and pointer arithmetic expression detector 3c
Consists of.

The operation appearance position detection unit 3a detects all operations having the same operands from the programs stored in the processing target storage unit 21. Specifically, the operation appearance position detection unit 3a compares operators and operands of all operations in the program held in the processing target holding unit 18 (if the operand is a variable, The contents of that variable are used for comparison.), And all the same operations are detected. After the detection, the operation appearance position detection unit 3a selects the operation expression located first in the operation expressions whose operation exists on the right side of the equal sign (this operation expression is referred to as a designated operation expression), and the cost extraction unit. Output to 7. Next, the positions of the second and subsequent arithmetic expressions are notified to the first arithmetic expression removing unit 13 (this arithmetic expression is called a common sub-expression). Further, the variables defined by the detected arithmetic expression are detected, and among these variables, the variable located first (this variable is referred to as the designated variable) is output to the first rewriting cost extraction unit 8, The second and subsequent variables (this variable is called a deletion variable) are output to the first value use position detector 4a.

The substitution appearance position detection unit 3b detects all arithmetic expressions for substituting constants for variables, or arithmetic expressions for substituting the values of variables for variables from the program held in the processing target holding unit 18, The position of the detected arithmetic expression is notified to the second arithmetic expression removing unit 15. Further, a variable (in the present embodiment, this variable is also referred to as a deletion variable) substituted by the detected arithmetic expression is detected, and the second value use position detection unit 4b and the second rewriting cost extraction unit 9 are detected. Output. Further, in the above arithmetic expression, the variables and constants present on the right side of the equal sign (in the present embodiment, these are also referred to as designated substitution numbers) are output to the second rewriting cost extraction unit 9.

The pointer arithmetic expression detection unit 3c detects all arithmetic expressions in which pointer variables are defined from the program held in the processing target holding unit 21. Specifically, the pointer arithmetic expression detection unit 3c detects all arithmetic expressions having pointer variables on the left side of the equal sign among the arithmetic expressions in the program held in the processing target holding unit 18. After the detection, the pointer operation expression detection unit 3c outputs the detected pointer variable to the third value use position detection unit 4c, and an operation that defines the pointer variable (this operation is called a pointer operation, a pointer operation and a pointer variable). An arithmetic expression including and is referred to as a pointer arithmetic expression) is detected and output to the third rewriting cost extraction unit 10. The position of the finally detected arithmetic expression is notified to the third arithmetic expression removing unit 17.

The value use position detector 4 comprises a first value use position detector 4a, a second value use position detector 4b, and a third value use position detector 4c. The first value use position detection unit 4a receives the deletion variable from the operation appearance position detection unit 3a, and the deletion variable is used as an operand (in the present embodiment, this operation is rewritten to perform an operation. This is called an expression.) Is detected. After the detection, the first value use position detection unit 4a determines whether a variable used as an operand is defined in the arithmetic expression in the area from the common subexpression to the rewriting arithmetic expression in the program. Check if it is not defined.
It is output to the rewriting cost extraction unit 8.

The second value use position detector 4b receives the deletion variable from the substitution appearance position detector 3b, and the deletion variable is
All arithmetic expressions used as operands (in the present embodiment, this arithmetic operation is also called a rewriting arithmetic expression) are detected and output to the second rewriting cost extraction unit 9. The third value use position detector 4c receives the pointer variable from the pointer arithmetic expression detector 3c, and the pointer variable is used as an operand (in this embodiment, this arithmetic operation is also rewritten). It is called an arithmetic expression.)
To detect all. After the detection, the third value use position detector 4c
Checks whether the variable used as the operand in the operation is defined in the area from the pointer variable to the rewrite operation expression in the program, and if it is not defined, the rewrite operation expression Is output to the third rewriting cost extraction unit 10.

The cost storage unit 5 stores the type of the arithmetic expression and the cost of the arithmetic expression corresponding to the type of the arithmetic expression. In the present embodiment, there are five items in which the types of the above arithmetic expressions are determined, and these items are search items for the cost extraction unit 7 and the first rewriting cost extraction unit 8 to perform a search. The cost storage unit 5 also stores costs corresponding to combinations of these search items. In FIG. 2, the target machine is a two-operand method, and the second to second
This is an example of what is called the irst method (method in which the second operand acts on the first operand). The above-mentioned search items are the operator type item, the operation type item, the operand on the right side of the operator (called the first operand), and the operand on the left side of the operator ( The second item is called the second operand, and the item of the storage location of the operation result is five items. In the above-mentioned operator type item, types of operators such as addition, subtraction, multiplication and division are shown. The operation type item is 8bit integer type,
Operation types such as 16-bit integer type, 32-bit integer type, single precision floating point type, double precision floating point type are shown. In the first and second types of operands, the operands store constants, static variables, static variables that store pointers, stack variables, stack variables that store pointers, register variables, and pointers. The types of variables such as register variables are shown.
The item of the storage location of the operation result shows the type of variable such as static variable, static variable that stores a pointer, stack variable, stack variable that stores a pointer, register variable, register variable that stores a pointer, etc. There is. In the cost item, the clock number of the machine language instruction corresponding to the conditions of these search items or the memory size is recorded.
In FIG. 2, the variable storing the pointer is described as a pointer in the item below.

The addressing cost storage unit 6 stores the cost of the machine language instruction using the addressing mode for the third rewriting cost extraction unit 10 to search. FIG. 3 shows an example of the addressing cost storage unit 6. The configuration of the addressing cost storage unit 6 is similar to that of the cost storage unit 5. The difference is that the addressing cost storage unit 6 has an item of the second operator and an item of the operand (third operand) on the right side of the second operator. The cost corresponding to the combination of one search item is stored.

The cost extraction unit 7 is a calculation appearance position detection unit 3
The cost storage unit 5 is searched with the specified arithmetic expression detected by a, and the cost of the machine language instruction corresponding to the arithmetic expression is extracted and output to the comparison unit 11. Specifically, the cost extraction unit 7
The specified arithmetic expression is received from the arithmetic appearance position detection unit 3a, the type of the variable used as the operand in the received specified arithmetic expression is checked, and whether the first and second operands are constants or static A static variable, a static variable that stores a pointer, a stack variable, a stack variable that stores a pointer, a register variable, or a register variable that stores a pointer . After checking these, the cost extraction unit 7 determines whether the storage location of the operation result is a static variable, a static variable storing a pointer, a stack variable, or a stack variable storing a pointer. Examine whether it exists, is a register variable, or is a register variable that stores a pointer. Based on the results of these investigations, the cost storage unit 5 is searched, and the corresponding cost is extracted and output to the comparison unit 11.

The first rewriting cost extracting unit 8 receives the designated variable from the operation appearance position detecting unit 3a, receives the rewriting arithmetic expression from the first value use position detecting unit 4a, and deletes the deletion variable in the rewriting arithmetic expression. , The cost storage unit 5 is searched by the rewritten arithmetic expression, the cost of the arithmetic expression is extracted and output to the comparison unit 11. For example, the variable a is a designated variable, the variable b is a deletion variable, and the arithmetic expression “d =
When “b + 3” is the rewriting arithmetic expression, the first rewriting cost extraction unit 8 rewrites the arithmetic expression “d = b + 3” into the arithmetic expression “d = a + 3” to search the cost storage unit 5,
The cost is taken out and output to the comparison unit 11. The method of searching for the cost performed by the first rewriting cost deriving unit 8 is the same as that of the cost deriving unit 7, and the description thereof will be omitted.

The second rewriting cost extraction unit 9 receives the deletion variable and the designated number of substitutions from the substitution appearance position detection unit 3b, receives the rewriting arithmetic expression from the second value use position detection unit 4b, and deletes the deletion variable. , It is determined whether or not the pointer is stored, and if so, the deletion variable in the rewriting arithmetic expression is rewritten to the specified number of substitutions, and the cost storage unit 5 is searched with the rewritten arithmetic expression and rewritten. The cost corresponding to the arithmetic expression is extracted and output to the comparison unit 11. For example, when the variable 3 is the designated substitution number, the variable b is the deletion variable, and the arithmetic expression “a = b + c” is the rewriting arithmetic expression, the first
The rewriting cost extraction unit 8 of the calculation “a = b + c”
The cost storage unit 5 is searched by rewriting the calculation to “a = 3 + c”, the cost is extracted, and the cost is output to the comparison unit 11. Second
The method of searching for the cost performed by the rewriting cost extracting unit 9 is the same as that of the cost extracting unit 7, and therefore the description thereof will be omitted.

The third rewriting cost extraction unit 10 receives the pointer variable and the pointer operation from the pointer arithmetic expression detecting unit 3c, receives the rewriting arithmetic expression from the third value use position detecting unit 4c, and writes the rewriting arithmetic expression in the rewriting arithmetic expression. Delete variables,
It is rewritten to a pointer operation, the addressing cost storage unit 6 is searched by the rewritten operation, and the cost of the machine language instruction in the addressing mode corresponding to the operation is fetched and output to the comparison unit 11. For example, the variable b is the number of designated substitutions, the designated calculation is “a + 2”, and the rewriting calculation formula is “d = b”.
+ C ”, the first rewriting cost extraction unit 8
The rewriting arithmetic expression “d = b + c” is calculated by the operation “d = a + 2 +
The addressing cost storage unit 6 is searched by rewriting to “c”, the cost is taken out, and output to the comparison unit 11. The method of cost search is the same as that of the cost extraction unit 7.

The comparing section 11 receives the costs extracted by the cost extracting section 7, the first cost rewriting extracting section 8, the second cost rewriting extracting section 9, and the third cost rewriting extracting section 10, and compares them with each other. To do. When the costs are received from the cost extraction unit 7 and the first cost rewriting extraction unit 8, the comparison unit 11 compares the costs. As a result of the comparison, if the cost taken out by the first rewriting cost extracting unit 8 is small, the first rewriting unit 12 is activated. Similarly, if the costs are received from the second cost rewriting and extracting unit 9 and the third rewriting cost extracting unit 10, the comparison unit 11
These are compared with the costs received from the cost retrieving unit 7, and if the costs retrieved by the second rewriting cost retrieval unit 9 and the third rewriting cost retrieval unit 10 are small, the second rewriting unit 14, the third rewriting unit 14 The rewriting unit 16 is activated.

The first rewriting unit 12 receives the designated variable from the operation appearance position detecting unit 3a, and designates the program position of the deletion variable in the rewriting arithmetic expression detected by the first value use position detecting unit 4a. Rewrite as a variable. When the first rewriting unit 12 rewrites all the deletion variables into the designated variables, the first arithmetic expression removing unit 13 calculates the operation appearance position detecting unit 3
The arithmetic expression of the position notified from a is deleted from the program.

The second rewriting unit 14 receives the deletion variable from the substitution appearance position detection unit 3b, and specifies the position on the program of the deletion variable in the rewriting arithmetic expression detected by the second value use position detection unit 4b. Rewrite with the number of substitutions. When the second rewriting unit 14 rewrites all the deletion variables into the designated variables, the second arithmetic expression removing unit 15 deletes the arithmetic expression at the position notified from the substitution appearance position detecting unit 3b from the program.

The third rewriting unit 16 receives the pointer operation from the operation appearance position detecting unit 3a, and indicates the position on the program of the pointer variable in the rewriting operation expression detected by the third value use position detecting unit 4c. Rewrite as calculation. The third arithmetic expression removing unit 17 includes a third rewriting unit 16
When all the deleted variables are rewritten to the designated variables, the pointer arithmetic expression at the position notified from the pointer arithmetic expression detection unit 3c is deleted from the program.

The processing object holding unit 18 holds the program to be processed. The stored program is written in the internal code generated by the compiler for the convenience of internal processing. The stored program may be written in source code written by a programmer.
The operation of the redundant removal device configured as described above will be described using examples from {Example 1} to {Example 3}.

{Example 1} As shown in FIG. 4, in the program,
Operation when there are a plurality of operations that perform exactly the same operation (1) The operation appearance position detection unit 3a includes the processing target holding unit 18
The specified arithmetic expression “g = f + 400” is detected from the program stored in FIG. 7 and the specified variable g is detected. Also, the arithmetic expression “h = f + 400” having the same arithmetic operation as the arithmetic operation “f + 400” on the right side of the equal sign is detected, and the deletion variable h is detected.

(2) The first value use position detection unit 4a receives the deletion variable h from the operation appearance position detection unit 3a, and the deletion variable h is used as a rewritten arithmetic expression "*". a = h * 70 ”is detected. (3) The cost extraction unit 7 searches the cost storage unit 5 with the rewriting arithmetic expression “* a = h * 70” detected by the value use position detection unit 4a, and extracts the cost of the machine language instruction corresponding to the calculation. And outputs to the comparison unit 11.

(5) The first rewriting cost extraction section 8
The specified variable g is received from the arithmetic appearance position detection unit 3a, and the rewriting arithmetic expression “* a =
h * 70 ”, the deletion variable h in the rewriting arithmetic expression is rewritten to the designated variable g, and the rewritten arithmetic expression“ * a
= G * 40 ”, the cost storage unit 5 is searched, and the cost of the arithmetic expression is extracted and output to the comparison unit 11.

(6) The comparing section 11 receives the costs extracted by the cost extracting section 7 and the first cost rewriting extracting section 8 and compares them with each other. In this case, since the cost received from the first rewriting cost extraction unit 8 is small,
The first rewriting unit 12 is activated. (7) The first rewriting unit 12 includes the calculation appearance position detecting unit 3
The designated variable g is received from a, and the deletion variable h of the rewriting arithmetic expression “* a = h * 70” detected by the first value use position detection unit 4a is rewritten to the designated variable g.

(8) The first arithmetic expression removing unit 13 rewrites the first rewriting unit 12, and then the arithmetic appearance position detecting unit 3a.
The arithmetic expression “h = f + 400” of the position informed from is deleted from the program. By the above operation, the program shown in FIG. 4 is rewritten to the program shown in FIG. {Example 2} Operation when there is an arithmetic expression for substituting a variable for a variable and an arithmetic expression for substituting a constant for a variable in a program as shown in FIG. 6 (1) The substitution appearance position detection unit 3b is shown in FIG. From the program shown, an arithmetic expression "f = 20" for substituting a constant for a variable is detected.

(2) The second value use position detection unit 4b receives the deletion variable from the substitution appearance position detection unit 3b, and the deletion variable is a rewriting arithmetic expression "g = f +" used as an operand. * A "is detected and output to the second rewriting cost extraction unit 9. (3) The cost extraction unit 7 uses the rewriting arithmetic expression “g = f + * a” detected by the value use position detection unit 4b to generate the cost storage unit 5.
Is retrieved, the cost of the machine language instruction corresponding to the arithmetic expression is extracted and output to the comparison unit 11.

(4) The second rewriting cost extraction unit 9
The deletion variable “f” and the designated substitution number “20” are received from the substitution appearance position detection unit 3b, and the rewriting arithmetic expression “g = f + * a” is received from the second value use position detection unit 4b, and the arithmetic expression “g” is received. = F + * a ”is changed to“ g = 20 + * a ”,
The cost of the machine language instruction corresponding to the rewritten arithmetic expression is extracted and output to the comparison unit 11.

(5) The comparing unit 11 receives the costs extracted by the cost extracting unit 7 and the second cost rewriting extracting unit 9 and compares them with each other. In this case, since the cost taken out by the second cost rewriting and taking-out unit 9 is small,
The rewriting unit 14 is started. (6) The second rewriting unit 14 includes the substitution appearance position detection unit 3
The designated substitution number "20" is received from b, and the deletion variable "f" in the rewriting arithmetic expression detected by the second value use position detection unit 4b is rewritten to the designated substitution number "20".

(7) The second arithmetic expression removing unit 15 rewrites the second rewriting unit 14 and then substitutes the appearance position detecting unit 3b.
The specified arithmetic expression “f = 20” for the position informed from is deleted from the program. When the redundant removal apparatus performs such processing, the program shown in FIG. 6 is rewritten as shown in FIG. {Example 3} As shown in FIG. 8, when there is a description in the program in which the address is calculated using the variable written as the pointer variable and the content of the calculated address is substituted into the variable (1) Pointer operation From the program shown in FIG. 8, the expression detection unit 3c uses the pointer arithmetic expressions “d = c + 400” and “d1.
= C * 400 ”is detected.

(2) The third value use position detector 4c receives the pointer variables "d" and "d" from the pointer arithmetic expression detector 3c.
1 ”, and the pointer arithmetic expression“ a = * (b +
d) ”and“ a = * (b + d1) ”are detected. (3) The cost extraction unit 7 includes the third value use position detection unit 4c
Rewriting arithmetic expression “a = * (b + d)”, “a
= * (B + d1) ”, the cost storage unit 5 is searched, and the cost of the machine language instruction corresponding to the arithmetic expression is extracted and output to the comparison unit 11.

(4) Third rewriting cost extraction unit 10
Are designated variables d, d1, from the pointer arithmetic expression detection unit 3c.
Receive the specified operation "c + 400", "c * 400",
From the third value use position detector 4c, the rewriting arithmetic expression "a =
"* (B + d)" and "a = * (b + d1)" are received, and the deleted variables d and d1 in the rewriting arithmetic expression are rewritten to the specified operations "c + 400" and "c * 400", and the rewritten arithmetic expression "a" = * (B + c + 400) ”,“ a = * (b
+ C * 400) ”, the cost storage unit 5 is searched, and the cost of the machine language instruction in the addressing mode corresponding to the operation is extracted and output to the comparison unit 11.

(5) The comparing section 11 receives the costs extracted by the cost extracting section 7 and the third cost rewriting extracting section 10 and compares them with each other. As a result of the comparison, since the cost taken out by the third rewriting cost extracting unit 8 is small, the third rewriting unit 10 is activated. (6) The third rewriting unit 16 includes the calculation appearance position detecting unit 3
The pointer calculation “c + 400”, “c * 400” is received from a, and the designated variable in the rewriting calculation expression detected by the third value use position detection unit 4c is rewritten to the pointer calculation.

(7) The third arithmetic expression removing unit 17 rewrites the third rewriting unit 16, and then the arithmetic appearance position detecting unit 3a.
The specified arithmetic expression “d = c + 400” of the position informed from
Delete "d1 = c * 400)" from the program. When such processing is performed, the program shown in FIG. 8 is rewritten as shown in FIG. The configuration of the redundant type removing device of the present invention is not limited to the above-described configuration, and the arithmetic expression including the second and subsequent operations among the operations detected by the operation appearance position detection unit 3a (redundancy formula)
Is searched for in the cost storage unit 5 by the type of the arithmetic expression and the cost corresponding to the type of the arithmetic expression is taken out by the redundant type cost take-out unit, the cost taken out by the cost take-out unit 7 and the redundant type cost take-out unit take out the cost. And a calculating unit for calculating the sum of the costs, and the comparing unit calculates the sum of the costs calculated by the calculating unit,
The first, second and third rewriting cost extraction units 8, 9 and 10 may be compared with the costs extracted to determine whether or not to rewrite and remove the redundant expression.

Further, the cost extraction unit 7, the first, second and third rewriting cost extraction units 8, 9 and 10 calculate the total sum of the extracted costs, and the comparison unit 11 compares the total sum of the thus calculated costs. Then, it may be determined whether or not to rewrite and remove the redundant expression. In addition, the redundant type cost extraction unit searches the cost storage unit 5 for the type of the arithmetic expression for the arithmetic expression including the second or later arithmetic operation among the arithmetic operations detected by the arithmetic appearance position detection unit 3a, and performs the operation. The cost corresponding to the type of expression is extracted, the cost extraction unit 7, the first, second, and third rewrite cost extraction units 8, 9, and 10 calculate the sum of the extracted costs, and the calculation unit sets the cost extraction unit 7 to The cost extraction unit 7 calculates the sum of the extracted costs and the cost extracted by the redundant cost extraction unit, and the cost extraction unit 7 calculates the sum of the costs calculated by the calculation unit and the first, second, and third rewriting cost extraction units. 8,
It is also possible to compare the total cost extracted by 9 and 10 and determine whether to rewrite and remove the redundant expression.

[0065]

As described above, according to the redundant expression removing apparatus of the present invention, the operand of the operation to be processed corresponds to any of a constant, a register variable, a stack variable and a static variable. Since the operator is rewritten after comparing the costs before and after the rewriting, the operation can be rewritten only when the rewriting of the operation is effective.

The processor of the target machine is
When addressing modes such as indirect address reference with index and offset, indirect address reference with offset, etc. can be used, the operation is rewritten to make effective use of these addressing modes, thus reducing the cost. The effect is that it can be achieved sufficiently.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an apparatus 10 of a redundant removal apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing the contents of a cost storage unit 5.

FIG. 3 is a diagram showing the contents of an addressing cost storage unit 6.

FIG. 4 is a diagram showing a program to be processed.

FIG. 5 is a diagram showing a program rewritten by the redundancy removing apparatus.

FIG. 6 is a diagram showing a program to be processed.

FIG. 7 is a diagram showing a program rewritten by the redundancy removing apparatus.

FIG. 8 is a diagram showing a program to be processed.

FIG. 9 is a diagram showing a program rewritten by the redundancy removing apparatus.

FIG. 10 is a diagram showing a configuration of a conventional redundant removal apparatus that deletes a common subexpression.

FIG. 11 is a diagram showing a program to be processed.

FIG. 12 is a diagram showing a program rewritten by a conventional redundant removal apparatus.

FIG. 13 is a diagram showing a configuration of a conventional redundant removal device that propagates a value.

FIG. 14 is a diagram showing a program to be processed.

FIG. 15 is a diagram showing a program rewritten by a conventional redundant removal apparatus.

FIG. 16 is a diagram showing correspondence between programs and addressing modes.

[Explanation of symbols]

 1 Control Unit 3a Calculation Appearance Position Detection Unit 3b Substitution Appearance Position Detection Unit 3c Pointer Arithmetic Expression Detection Unit 4a First Value Use Position Detection Unit 4b Second Value Use Position Detection Unit 4c Third Value Use Position Detection Unit 5 Cost Storage unit 6 Addressing cost storage unit 7 Cost extraction unit 8 First rewriting cost extraction unit 9 Second rewriting cost extraction unit 10 Third rewriting cost extraction unit 11 Comparison unit 12 First rewriting unit 13 First arithmetic expression Removing unit 14 Second rewriting unit 15 Second arithmetic expression removing unit 16 Third rewriting unit 17 Third arithmetic expression removing unit 18 Processing target holding unit

Claims (19)

[Claims] Claims: 1. A redundant type elimination device, which is provided in a compiler, rewrites an operation of a program held in a program holding means, and removes a redundant arithmetic expression after the rewriting. An operation detecting means for detecting all operations whose children and operands are the same, detecting all variables defined by the operations, and storing the position of the operation expression including the detected operation and the variables; Among the variables detected by the detection means, the second and subsequent variables are the operand detection means for detecting all operations used as operands, the type of the arithmetic expression, and the type of the arithmetic expression are these The cost storage means for storing the cost of the arithmetic expression corresponding to the type and the cost storage means for the type of the arithmetic expression detected by the operand detection means are searched, and the cost corresponding to the type of the arithmetic expression is retrieved. The first cost extracting means and the arithmetic expression type in the case where the first variable of the variables detected by the operation detecting means is used as the operand of the arithmetic expression detected by the operand detecting means. A second cost extraction unit that retrieves the cost corresponding to the type of the arithmetic expression by searching the cost storage unit, a cost extracted by the first cost extraction unit, and a cost extracted by the second cost extraction unit If the cost extracted by the second cost extraction means is small as a result of comparison between the comparison means for comparison and the comparison means, in the program of the variable used as the operand by the operation detected by the operand detection means. Rewriting means for rewriting the position of No. 1 to the variable detected first by the operation detecting means, and when the rewriting means rewrites all the variables under operation detected by the operand detection means, the operand detection means Redundant expression removing device, comprising: a removing means for removing an arithmetic expression including a variable used as an operand in an operation detected by the operator and an operation in which the variable was defined from a program. . 2. A first cost extracting means obtains a total of extracted costs, a second cost extracting means obtains a total of extracted costs, and a comparing means obtains the first cost extracting means. 2. The redundant removing apparatus according to claim 1, wherein the sum of the costs is compared with the sum of the costs obtained by the second cost extracting means. 3. The redundancy according to claim 1, wherein the comparison means compares the individual costs extracted by the first cost extraction means with the individual costs extracted by the second cost extraction means. Type removal device. 4. A redundant type elimination device, which is provided in a compiler, rewrites an operation of a program held in a program holding means, and removes a redundant arithmetic expression after the rewriting, wherein the program is stored in the program holding means. An operation detecting means for detecting all operations whose children and operands are the same, detecting all variables defined by the operations, and storing the position of the operation expression including the detected operation and the variables; Among the variables detected by the detection means, the second and subsequent variables are the operand detection means for detecting all operations used as operands, the type of the arithmetic expression, and the type of the arithmetic expression are these The cost storage means for storing the cost of the arithmetic expression corresponding to the type and the cost storage means for the type of the arithmetic expression detected by the operand detection means are searched, and the cost corresponding to the type of the arithmetic expression is retrieved. The cost storage means is searched for with the first cost extraction means and the operation expression type for the operation expression including the second or later operation among the operations detected by the operation detection means, and the type of the operation expression is obtained. A calculating means for obtaining the sum of the costs taken out by the redundant type cost taking means for taking out the corresponding costs and the first cost taking means and the costs taken out by the redundant type cost taking means, and the arithmetic expression detected by the operand detection means The cost storage means is searched for by the type of the arithmetic expression when the variable located first among the variables detected by the arithmetic detection means is used as the operand of, and the cost corresponding to the type of the arithmetic expression is extracted. As a result of the comparison between the sum of the cost extraction means of No. 2 and the cost obtained by the calculation means and the cost extracted by the second cost extraction means and the comparison means, the second cost extraction means extracted. If the cost is small, the position in the program of the variable used as the operand in the operation detected by the operand detection means,
When the rewriting means rewrites all variables in the operation detected by the operand detecting means and the rewriting means that rewrites to the variable detected first by the operation detecting means, the operation detected by the operator detecting means is used as the rewriting means. A redundant expression removing apparatus comprising: a removing unit that removes an arithmetic expression including a variable used as an operator and an operation in which the variable is defined from a program. 5. The first cost take-out means obtains the total sum of the taken out costs, and the calculating means takes the sum of the costs taken out by the first cost taking means and the cost taken out by the redundant type cost take-out means. The second means of taking out the cost is
5. The sum total of the extracted costs, and the comparing means compares the sum of the costs calculated by the calculating means with the sum of the costs calculated by the second cost extracting means.
Redundant removal device as described. 6. The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the cost taken out by the redundant cost taking means, and the comparing means gives the sum of the costs found by the calculating means. 5. The redundant removal device according to claim 4, characterized in that the individual cost calculated by the second cost extracting means is compared with the individual cost. 7. A redundant type removing device, which is provided in a compiler, rewrites the operation of a program held in the program holding means, and removes redundant arithmetic expressions after the rewriting, which is held in the program holding means. From the program
There is an arithmetic expression for substituting a constant for a variable and an arithmetic expression detecting means for detecting all arithmetic expressions for substituting a variable value for a variable, and a variable existing on the left side of the equal sign of the arithmetic expression detected by the arithmetic expression detecting means , Operand detection means for detecting all the arithmetic expressions used as operands from the program holding means, the type of the arithmetic expression, and the cost of the arithmetic expression whose arithmetic expression type corresponds to these types are stored. The cost storage means and the first cost extraction means for searching the cost storage means by the type of the arithmetic expression detected by the operand detection means and extracting the cost corresponding to the type of the arithmetic expression, and the operand detection means The cost storage means is searched by the type of the arithmetic expression when the variable located first in the variables detected by the arithmetic expression detecting means is used as the operand of the detected arithmetic expression,
Second cost extraction means for extracting a cost corresponding to the type of the arithmetic expression, comparison means for comparing the cost extracted by the first cost extraction means with the cost extracted by the second cost extraction means, If the cost taken out by the second cost take-out means is small as a result of the comparison means comparing the cost taken out by the first cost take-out means with the cost detected by the second cost take-out means, Rewriting means for rewriting the position in the program of the variable used as the operand in the operation detected by the operand detection means to the variable or constant detected by the arithmetic expression detection means, and the operand detection means detected When the rewriting means rewrites all the variables in the calculation, the variable used as the operand in the calculation detected by the operand detection means exists on the left side of the equal sign. And a removal unit that removes the calculation formula detected by the calculation formula detection unit from the program. 8. A first cost extraction means calculates a total of extracted costs, a second cost extraction means calculates a total of extracted costs, and a comparison means calculates a first cost extraction means. 8. The redundant removing apparatus according to claim 7, wherein the sum of the costs is compared with the sum of the costs obtained by the second cost extracting means. 9. The redundancy according to claim 7, wherein the comparison means compares the individual costs extracted by the first cost extraction means with the individual costs extracted by the second cost extraction means. Type removal device. 10. An operation of a program held in a program holding means provided in a compiler is rewritten,
A redundant type removal device for removing redundant arithmetic expressions after rewriting, wherein the program stored in the program storage means is
There is an arithmetic expression for substituting a constant for a variable and an arithmetic expression detecting means for detecting all arithmetic expressions for substituting a variable value for a variable, and a variable existing on the left side of the equal sign of the arithmetic expression detected by the arithmetic expression detecting means , Operand detection means for detecting all the arithmetic expressions used as operands from the program holding means, the type of the arithmetic expression, and the cost of the arithmetic expression whose arithmetic expression type corresponds to these types are stored. The cost storage means and the first cost extraction means for searching the cost storage means by the type of the arithmetic expression detected by the operand detection means and extracting the cost corresponding to the type of the arithmetic expression, and the arithmetic expression detection means The cost storage means is searched by the type of the arithmetic expression of the arithmetic expression and the cost corresponding to the type of the arithmetic expression is extracted by the redundant type cost extracting means and the first cost extracting means, and the redundant type cost extracting means. Taken out The type of the arithmetic expression in the case where the first variable among the variables detected by the arithmetic expression detecting means is used as the operand of the arithmetic expression detected by the calculating means for obtaining the sum The second cost extraction means for searching the cost storage means with to extract the cost corresponding to the type of the arithmetic expression, the sum of the costs calculated by the calculation means and the cost extracted by the second cost extraction means As a result of the comparison between the comparison means and the comparison means, if the cost extracted by the second cost extraction means is small, the position in the program of the variable used as the operand in the operation detected by the operand detection means is determined. , Rewriting means for rewriting to the variable or constant detected by the arithmetic expression detection means, and when the rewriting means rewrites all the variables in the operation detected by the operand detection means, the operand detection means detects The variable used as the operand in the arithmetic operation is an arithmetic expression existing on the left side of the equal sign, and the arithmetic expression detected by the arithmetic expression detecting means is removed from the program. Characteristic redundant removal device. 11. The first cost take-out means obtains the total sum of the taken out costs, and the calculating means takes the sum of the costs taken out by the first cost take-out means and the cost taken out by the redundant type cost take-out means. The second cost extraction means calculates the sum of the extracted costs, and the comparison means compares the sum of the costs calculated by the calculation means and the sum of the costs calculated by the second cost extraction means. The redundant removing device according to claim 10, wherein 12. The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the costs taken out by the redundant cost taking means, and the comparing means takes the sum of the costs obtained by the calculating means. 11. The redundant removal device according to claim 10, wherein the cost is compared with the individual cost obtained by the second cost extraction means. 13. An operation of a program held in a program holding means provided in a compiler is rewritten,
A redundant expression removing device for removing a redundant arithmetic expression after rewriting, wherein an arithmetic expression in which a variable that is a pointer is defined is detected from a program of a program holding means, and the detected arithmetic operation and an arithmetic expression including the variable are detected. , An operation detecting means for storing the position of, an operator detecting means for detecting all arithmetic expressions used as operands by variables detected by the operation detecting means, and an operation executable by one machine language instruction The type of an expression that includes at least two operands among the operands used for pointers, the operands used for indexes, and the operands used for offsets, and the operation A cost storage means for storing the cost of the arithmetic expression corresponding to the type of the expression, and an arithmetic expression corresponding to the arithmetic expression searched for in the cost storage means by the arithmetic expression detected by the operand detection means. Cost storage means in the form of an arithmetic expression when the operation detected by the operation detection means is applied to the operand of the arithmetic expression detected by the operand detection means and the first cost extraction means for extracting the cost And a comparing means for comparing the cost extracted by the first cost extracting means with the cost extracted by the second cost extracting means. As a result of comparison by the comparison means, if the cost extracted by the second cost extraction means is small, the position in the program of the variable used as the operand is calculated by the arithmetic expression detected by the operand detection means, The rewriting means for rewriting the operation detected by the operation detecting means, and the variables in all the operation expressions detected by the operand detection means,
A redundant type removing device comprising: a removing unit that removes an arithmetic expression including an operation detected by the operation detecting unit from a program when the rewriting unit rewrites. 14. A first cost extracting means obtains a total of extracted costs, a second cost extracting means obtains a total of extracted costs, and a comparing means obtains the first cost extracting means. 14. The redundant removal apparatus according to claim 13, wherein the total sum of the costs is compared with the total sum of the costs obtained by the second cost extracting means. 15. The redundancy according to claim 13, wherein the comparison means compares the individual costs extracted by the first cost extraction means with the individual costs extracted by the second cost extraction means. Type removal device. 16. A rewriting operation of a program held in a program holding means, which is provided in a compiler,
A redundant expression removing device for removing a redundant arithmetic expression after rewriting, wherein an arithmetic expression in which a variable that is a pointer is defined is detected from a program of a program holding means, and the detected arithmetic operation and an arithmetic expression including the variable are detected. , An operation detecting means for storing the position of, an operator detecting means for detecting all arithmetic expressions used as operands by variables detected by the operation detecting means, and an operation executable by one machine language instruction The type of an expression that includes at least two operands among the operands used for pointers, the operands used for indexes, and the operands used for offsets, and the operation A cost storage means for storing the cost of the arithmetic expression corresponding to the type of the expression, and an arithmetic expression corresponding to the arithmetic expression searched for in the cost storage means by the arithmetic expression detected by the operand detection means. The cost storage means is searched for with a first cost extraction means for extracting the cost of the cost and an operation expression type of an operation expression including an operation positioned second and later among the operations detected by the operation detection means, and the operation expression Of the redundant type cost take-out means for taking out the cost corresponding to the type of the first cost take-out means, and the cost taken out by the redundant type cost take-out means The cost storage means is searched with the type of the arithmetic expression when the variable located first in the variables detected by the arithmetic detection means is used as the operand of the arithmetic expression, and the cost corresponding to the type of the arithmetic expression is searched. The second cost extraction means compares the sum of the costs obtained by the second cost extraction means with the calculation means and the cost extracted by the second cost extraction means with the comparison means and the comparison means. If the cost taken out by the means is small, rewriting means for rewriting the position in the program of the variable used as the operand in the arithmetic expression detected by the operand detecting means to the operation detected by the arithmetic detecting means, Variables in all arithmetic expressions detected by the operand detection means,
A redundant type removing device comprising: a removing unit that removes an arithmetic expression including an operation detected by the operation detecting unit from a program when the rewriting unit rewrites. 17. The first cost take-out means obtains the total sum of the taken-out costs, and the calculating means takes the sum of the costs taken out by the first cost take-out means and the cost taken out by the redundant type cost take-out means. The second cost extraction means calculates the sum of the extracted costs, and the comparison means compares the sum of the costs calculated by the calculation means and the sum of the costs calculated by the second cost extraction means. 17. The redundant removal device according to claim 16, wherein: 18. The calculating means obtains the sum of the individual costs taken out by the first cost taking means and the costs taken out by the redundant type cost taking means, and the comparing means takes the sum of the costs obtained by the calculating means. 17. The redundant removal device according to claim 16, characterized in that the individual cost calculated by the second cost extraction means is compared with the individual cost. 19. The cost stored in the cost storage means is an execution time and / or a memory size of a machine language instruction corresponding to a type of an arithmetic expression.
22. The redundant removal device according to any one of 18 to 18.