JPH0421030A - Detection object generating system for reference of outside of declaration range of array - Google Patents

Abstract

PURPOSE:To execute the DO loop by a vector computer by generating an object for detecting efficiently whether a range referred to in the DO loop to an array is included in a declaration range or not, and setting it immediately before the DO loop. CONSTITUTION:An array reference detecting means 10 checks up all operations in a DO loop, decides whether it is a reference of an array element or not, and an array reference pattern deciding means 20 checks up a subscript expression of an array reference table recorded by the array reference detecting means 10, and decides whether a method for referring to an array element is expressed by a linear expression of a constant coefficient of a loop control variable of the DO loop or not. Subsequently, an object 9 for comparing the minimum value of a reference range to an array and the minimum value of a range in which the array is declared and comparing the maximum value of the reference range to the array and the maximum value of the range in which the array is declared, in accordance with the method for referring to the array element is set immediately before the DO loop. In such a way, the DO loop can be executed by a vector computer.

Description

[Detailed Description of the Invention] 1゜[Industrial Application Field] This invention relates to a compiler that converts a computer language such as FORTRAN into machine language, and especially when referring to an area outside the declared range of an array. This invention relates to a compilation method for generating detection objects for notification by message.

[Conventional technology]

Computer languages such as FORTRAN have long been known to have a function that notifies the user of this by sending a message when a program refers to an area outside the range of an array declared by the user.

That is, as shown in Figure 2, the size of array A is 10
is declared, and when A(11) is referenced in the DO loop, if the option to instruct the detection of references outside the declaration range of the array is specified, A(11) outside the declaration range is specified.
The user is notified as an error message that the array has been referenced, and the user can be made aware of the out-of-declaration range reference of the array.

As a method to implement this function for detecting references outside the array declaration range, the compiler creates an object that determines whether the value of the subscript representing the referenced array element is within the declaration range of the array, immediately before referencing an array element. A method is known in which a program is generated and this determination is made when the program is executed.

However, in this conventional method, since the determination object is executed every time an array is referenced, there is a problem in that the execution time is much longer than when the above function is not specified.

Furthermore, in recent years, vector computer type supercomputers have been widely used, and they are capable of executing calculations during a DO non-loop at a high speed all at once. However, when the above function is specified, a judgment object for a reference outside the array declaration range is generated during the DO non-loop, so
There was a problem that the effect of vectorization was lost.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for generating an object that efficiently detects references outside the declaration range of arrays in a compiler for a computer language such as FORTRAN.

In other words, even if an option that instructs the detection of out-of-scope array declaration references is specified, the execution time will hardly increase compared to when the option is not specified. The purpose is to provide a means.

Another object of the present invention is to generate an object that efficiently detects whether the range referenced in a DO loop for an array is within the declaration range, set it immediately before the DO loop, and set it immediately before the DO loop. It is an object of the present invention to provide a means for not including a detection object in a DO non-loop so that the DO loop can be executed by a vector computer.

[Means to solve the problem]

In order to achieve the above object, in a compiler for a computer language such as FORTRAN, an array reference detection means for detecting a reference point of an array element in a DO loop, and a DO small loop control variable that determines how the array element is referenced. an array reference pattern determination means for determining whether or not the array is expressed by a linear expression with constant coefficients, and the minimum value of the reference range for the array and the declared range of the array depending on how the array element is referenced Comparison object generation means is provided for setting an object immediately before the DO small loop to perform comparison with the minimum value of , and the maximum value of the reference range for the array with the maximum value of the declared range of the array.

[Effect]

In a compiler for a computer language such as FORTRAN, the above three means operate as follows.

The array reference detection means examines all operations in the DO loop, determines whether they are references to array elements, and if they are references to array elements, identifies the name of the array and where in the array it refers to. The expressions (called subscripts and expressions) that represent whether the

The array reference pattern determining means examines the subscript expression of the array reference table recorded by the array reference detecting means, and determines whether the method of referencing the array element is expressed by a linear expression of a constant coefficient of the DO non-loop loop control variable. Determine whether or not. here,
The linear expression of the constant coefficient of the DO non-loop loop control variable is
When the loop control variable is I, it is expressed as C1*I+C2. Here, C1 is a constant, and C2 is a constant or a loop-invariant variable. When C1 is not a constant but a loop-invariant variable, it is not considered to be a linear expression with constant coefficients. The comparison object generation means compares the minimum value of the reference range for the array with the minimum value of the declared range of the array, depending on the method of referencing the array element determined by the above-mentioned array reference pattern determination means; An object is generated that compares the maximum value of the reference range for the array with the maximum value of the declared range of the array, and is set immediately before the DO non-loop. There are two types of comparison objects that are generated:

(1) In the case of a linear formula for the constant coefficient of the loop control variable, by the initial value Ii and final value Ie of the loop control variable, the linear formula for the constant coefficient of the loop control variable (C1 * I + C2)
The minimum value Es and maximum value E1 are determined as follows.

■When C1 is positive, minimum value Es=01*Ii×C2゜Maximum value E1=C1*Ie×■When C1 is negative, minimum value E 5=c1*I e×0
2° Maximum value E1 = C1 * Is + C2° Note that the minimum value of the declared range of the array is Ls.

Let the maximum value be Ll.

The generated comparison object is as follows.

IF(El>Ll, OR, Es<Ls) THENCAL
L ERRMSG where the ERRMSG routine is the name of the error message output routine.

(2) When the loop control variable (2) is not a linear expression of a constant coefficient In this case, the minimum and maximum values of the reference range of the array in the DO loop cannot be determined by the expression. Immediately before the DO loop, create an o loop as shown below, find the minimum and maximum values of the reference range, and then compare them with the minimum and maximum values of the declared range of the array. Generate an object.

Let E(I) be the subscript expression for array reference in the original DO loop.

Emax=L L Emin=Ls DO 10 I=Ii, Ie i F, (Emax<E (I)) THENE
max=E (I) I F (Emin>E (I)) THENEmin
=E (I) 10 C0NTINUE IF (Emax)Ll, OR, Emin<Ls) THEN CALL ERRMSG When executing this on a vector calculator, the following vector executable object is generated in place of the above object.

Emax=VMAX (I=I i, I e)E (I
) Emin=VMIN (I=I i, I e) E (
I) IF (Emax>L 1, ORoEmi
n<L 5) THEN CALL ERRMSG
Here, VMAX and VMIN represent vector operations for obtaining the maximum value and minimum value, respectively.

By executing the comparison object as a vector, references outside the declaration range of arrays can be detected quickly.

Note that if there are multiple subscript expressions for array references in the original DO loop, the maximum and minimum values of the multiple subscript expressions may be determined and multiple IF statements may be generated.

As it operates as described above, it is possible to generate an object that quickly detects references outside the declaration range of an array. Furthermore, in the case of vector execution, an object that detects references outside the declaration range of the array is generated immediately before the DO loop, and an object that detects references outside the declaration range of the array is not generated in the original DO loop. , the original DO loop can be vector-implemented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a source program written in a computer language such as FORTRAN, 2 is a compiler, and 9 is an object program generated by the compiler 2. In FIG. The compiler 2 includes a syntax analysis unit 3 and an optimization unit 4.
, a vectorizer 5, and a code generator 6. sauce·
The program 1 is analyzed by the syntax analysis unit 3 and converted into intermediate language 8 on the main storage device 7 . The intermediate language 8 is converted by the optimization unit 4 and the vectorization unit 5 into a form with good execution performance, and finally the code generation 8116 performs register allocation and storage allocation, and then the object 9 is generated. The above operation is conventionally known, so a description thereof will be omitted.

One method of generating a detection object for a reference outside the declaration range of an array according to the present invention is to use the optimization unit 4. Another method is to use the vector north 5. The present invention, which efficiently detects references outside the declaration range of arrays, is most effective when generating objects to be executed on a vector computer, so here we will use the vectorization unit 5.
A case will be described in which a detection object is generated.

The vectorization unit 5 includes: (1) an array reference detection unit 10 that detects the reference location of an array element in a DO loop; (2) the method of referencing the array element is based on the constant coefficient of the loop control variable of the DO loop; Array reference pattern determination unit 2 that determines whether or not it is expressed by a linear expression (3) Whether or not the reference range for the array is included in the declared range according to the way the array element is referenced A comparison object generation unit is placed immediately before the DO loop to set an object to be compared and detected. They work as follows.

The array reference detection unit 10 operates as follows for each DO loop.

That is, all operational elements of all statements within the DO loop are examined to determine whether they are references to array elements. If an array element is referenced, the name of the array and an expression (referred to as a subscript expression) representing where in the array is referred to are recorded as an array reference table.

The array reference pattern determination unit 20 first examines the subscript expressions of each array reference table recorded by the array reference detection unit 10 described above. In other words, the method of referencing the array element is
It is determined whether the constant coefficient of the loop control variable of the O-loop is expressed by a linear expression.

Here, the linear expression of the constant coefficient of the loop control variable of the DO loop is C1*I102 when the loop control variable is
means something that is expressed as Here, C1 is a constant, and C2 is a constant or a loop-invariant variable. When C1 is not a constant but a loop-invariant variable, it is not considered to be a linear expression with constant coefficients.

Here, since the method of determining whether C1 and C2 are constants and the method of determining whether C2 is a loop-invariant variable are well known, the details will be omitted.

Next, the comparison object generation unit 30 determines the minimum value of the reference range for the array and the minimum value of the declared range of the array, depending on the method of referencing the array element determined by the above-described array reference pattern determination unit 20. An object that performs comparison with the value and the maximum value of the reference range for the array and the maximum value of the declared range of the array is generated and set immediately before the DO small loop.

There are two types of comparison objects that are generated:

(1) In the case of a linear equation with a constant coefficient of loop control variable 1 An example is shown in FIG.

In the figure, the initial value of the loop control variable (■) is Ii, and the final value is Ie. Also, subscript expression 31 is the loop control variable ■
It is expressed as a linear equation (C1*I102) with constant coefficients. The minimum value Es and maximum value El of the subscript expression 31 are determined as follows.

■When C1 is positive, the minimum value Es = C1 * Ii + C2° Maximum value E1=c1*Ie1 ■When C1 is negative, the minimum value ES = C1 * Ie + C2° Maximum value E1 = C1 * Is ten Note that the minimum value of the declared range of the array is Ls.

Let the maximum value be Ll.

The compiler determines whether C1 is positive or negative.

Here, a case where C1 is positive will be shown. The generated comparison object 32 is as follows.

E1=C1*Ie+C2 E5=C1*Ii+C2 IF (El>Ll, OR, Es<Ls) THENCAL
L ERRMSG where the ERRMSG routine is the name of the error message output routine.

(2) Case where the loop control variable ■ is not a linear expression with a constant coefficient This will be explained using FIG. In the figure, the subscript expression 41 of array A is determined by the values in the array.

In the second case, the minimum and maximum values of the reference range of the array in the DO loop cannot be determined by formulas. In this case, the DO
Immediately before the loop, generate an o loop as shown below, find the minimum and maximum values of the reference range, and then create the following object to compare with the minimum and maximum values of the declared range of the array. generate.

Subscript expression 41% expression of array reference in original DO loop) When executing this with a vector calculator, the next vector-executable object 42 is generated in place of the above object.

Emax=VMAX (I=I i, I e)L (I
)Emin=VMIN (I=I i, I e)L (
I) IF (Emax)Ll, OR, Emin<Ls)
THEN CALL ERRMSG where VMA
X and VMIN represent vector operations for finding the maximum value and minimum value, respectively.

By executing the comparison object as a vector, references outside the declaration range of the array can be detected at high speed.

As explained above, according to this embodiment, for array references within a DO loop, the object that detects references outside the declaration range is performed only once for the DO loop. Therefore, it is possible to prevent a decrease in execution speed compared to when references outside the declaration range are not detected. Furthermore, since the original DO loop can be executed vectorwise, references outside the declaration range of arrays can be detected, and the performance of the vector computer can be fully utilized.

〔Effect of the invention〕

According to the present invention, it is possible to provide an object generation method that efficiently detects a reference outside the declaration range of an array.

In other words, even if an option that instructs the detection of out-of-scope array declaration references is specified, the execution time will hardly increase compared to when the option is not specified. means can be provided.

Furthermore, create an object that efficiently detects whether the range referenced within the DO loop for the array is within the declaration range, and set it immediately before the DO loop,
Since the DO loop does not include a detection object, it is possible to provide a means for executing the DO loop with a vector computer.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a compiler to which the present invention is applied. Figure 2 is a diagram showing an example of a program with a reference outside the declaration range of an array. Figure 3 is a diagram in which the subscript expression of an array reference is a loop control variable. Figure 4 shows an object that detects a reference outside the declaration range of an array when the constant coefficient linear expression is a constant coefficient linear expression. FIG. 3 is a diagram illustrating an object that detects an external reference. 1... Source program, 2... Compiler, 3
...Syntax analysis unit, 4...Optimization unit, 5...Vectorization unit, 6...Code generation unit, 7...Main storage device, 8
...Intermediate language, 9...Generated object, 10
...Array reference detection unit, 20...Array reference pattern version bottom, 30.Comparison object generation unit, 31.41.
Subscript expression, 32.42... Comparison object.

Claims (1)

[Claims] 1. In a compiler for a computer language such as FORTRAN, there is an array reference detection means that detects the reference point of an array element in a DO loop, and the method of referencing the array element is linear in the constant coefficient of the loop control variable of the DO loop. Array reference pattern determining means for determining whether or not it is expressed by an expression;
Comparison of the minimum value of the reference range for the array and the minimum value of the declared range of the array, and the comparison of the maximum value of the reference range for the array and the declared range of the array, depending on how the array element is referenced. 1. A detection object generation method for a reference outside the declaration range of an array, characterized in that a comparison object generation means is provided for setting an object to be compared with a maximum value immediately before the DO loop.