JPH02105224A - Data allocation system in compiler - Google Patents

Abstract

PURPOSE:To perform the optimum allocation of data on a memory in compilation by providing a data allocation means with allocation decision function, and allocating the data by referring to an allocation bit in a data name table. CONSTITUTION:A front end processor 2, in the case of inputting a source program 1, outputs a text & table 3 including the data name table by performing the processing of syntax analysis, etc. Next, a back end processor 4 reads in the table 3 by an input means 5, and starts up the data allocation means 6 with allocation decision function in the case of detecting a procedure text including the reference of the data. The means 6 refers to the allocation bit attached on the data name table in the table 3 for referred data, and performs the allocation of the data on the memory when a value representing incompletion is OFF, and performs no allocation when the value representing completion is ON. In such a manner since no allocation is applied on the data on which the allocation is applied once even when reference is repeated, it is possible to perform the optimum allocation of the data on the memory in the compilation, and to improve processing capacity.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for allocating data to memory in a compiler used in a computer system. [Prior Art] Fig. 3 shows the configuration of a conventional compiler. It is
When the front end 32 inputs the source program 31, it performs processing such as syntactic analysis and semantic analysis and outputs a text & table 34 including intermediate text and various tables, and data allocation is declared in the source program 31 by means 33. (including implicit declarations,
) are allocated to memory in the order in which they are declared, and control is passed to the bank end 35. The back end 35 reads the text & table 34 using the input means 36, converts it into the corresponding code using the code generation means 37, and transfers control to the bank end 35. Target program 3B was being generated.

[Problem to be solved by the invention]

Conventional compilers were configured and operated as described above, but data allocation in the front end 32 was performed using means 3.
3, all the data declared in the source program 31 was unconditionally allocated to memory, so a memory area was reserved even for unnecessary data that was not actually referenced in the procedure statement, and the target program 38
This has the disadvantage that the memory resources that can be used during execution are reduced by that amount, leading to a decrease in processing power and efficiency.

The present invention has been proposed in view of the above points, and its purpose is to provide a method for data allocation in a compiler that can optimally allocate data to memory during compilation.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a method for allocating data to memory in a compiler that inputs a source program and generates a target program, and a method for allocating data to a data name table for data declared in the source program. Before code generation, refer to the data name table for the referenced data and allocate the data to memory only if the allocated bit is unfinished, and the allocation is completed. I am trying to change the bit to already done.

That is, in the present invention, unnecessary data allocation is prevented by allocating data to memory only for data that is actually referred to in a procedure statement. Note that if you allocate all the data that is actually referenced, it will cause problems if the same data is referenced multiple times, so by introducing the already allocated bit, it is possible to allocate data to the same data more than once. I try not to do it.

[Effect]

The method of data allocation in the compiler of the present invention is to add an already allocated bit to the data name table for the data declared in the source program, perform the data allocation before code generation, and The data name table is referred to for the data actually referred to in the sentence, and data is allocated to the memory only when the allocated bit is not yet completed, and the allocated bit is changed to already completed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a compiler that uses the data allocation method of the present invention. In FIG. 1, this embodiment consists of a front end 2 that inputs a source program 1 and outputs a text and table 3, and a back end 4 that inputs the text and table 3 and generates and outputs a target program 8. It is configured. Further, the back end 4 is composed of an input means 5, a data allocation means 6 with a function for determining whether allocation has been completed, and a code generation means 7. Note that the front end 2 includes well-known syntactic analysis means, semantic analysis means, and the like.

When the front end 2 receives the source program 1, it performs processes such as syntactic analysis and semantic analysis, and outputs a text table 3 including intermediate text and various tables. The table contains a data name table for all of the data declared in the source program z. The data name table stores data names and various information related to the data in correspondence with each other.Furthermore, in the present invention, the data name table is information that indicates whether or not the data has already been allocated to the memory. B.

has been added. Note that in the initial state, the allocated bit stores a value indicating that the allocation has not been completed (for example, 0FF). Here, for example, if there is a statement written as -B in the source program l, and this is a language specification that assigns the contents of data B to data A, then Text & Table 3 contains information indicating the procedure of assignment. and a data name table regarding data A and B.

Next, the back end 4 inputs the text &
When reading the table 3 and detecting a procedure statement that references data, the data allocation means 6 with a function for determining whether the allocation is completed is activated.

FIG. 2 is a flowchart showing the processing of the data allocation means 6 with the function of determining that the allocation has been completed, and the activated data allocation means 6 with the function of determining that the allocation has been completed is a flowchart showing the processing of the data allocation means 6 with the function of determining that the allocation has been completed. Refer to the allocated bit (step 21), and if the value indicates that the allocation has not been completed (OFF), data is allocated to the memory (step 2).
2) Set the assignment completion bit of the data name table corresponding to the data to a value indicating assignment completion (ON) (Step 2)
3) Also, in step 21, if the Allocation Completed bit of the data name table corresponding to the referenced data is a value indicating Allocation Already (ON), the data allocation has already been completed for that data. Ends processing without performing data allocation. By doing this, the data that has been allocated will not be allocated again no matter how many times it is subsequently referenced, but will only be allocated the first time it is referenced.

Next, returning to FIG. 1, the back end 4 uses the code generation means 7 to convert the allocated data and the information of the text & table 3 into corresponding codes to generate the target program 8. Text & Table 3
This is done for all procedural statements in , and the compiler processing ends.

〔Effect of the invention〕

As explained above, in the data allocation method in the compiler of the present invention, for the data actually referenced in the procedure statement, the allocated bit of the data name table is referred to, and the data is allocated only for the first time. Since the allocation is performed, the memory is not held by &1 for unnecessary data that is not actually referenced, and the effect is that memory resources can be used effectively and processing capacity can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a compiler that uses the data allocation method of the present invention, and FIG. FIG. 3 is a block diagram showing a conventional compiler. In the figure, 1... Source program 2... Front end 3... Text & table 4... Back end 5... Input means 6... Data allocation with a function to determine that the allocation is complete is performed by means 7.
...Code generation means 8...Target program

Claims (1)

[Claims] In a data allocation method for memory in a compiler that generates a target program by inputting a source program, an allocated bit is added to a data name table for data declared in the source program, and a code Before generation, the data name table is referred to for the referenced data, and only if the allocated bit is unfinished, the data is allocated to the memory, and the allocated bit is changed to the allocated bit. data allocation method in the compiler.