JPH07141196A - Loop developing system having out-of-loop branch - Google Patents

Abstract

PURPOSE:To reduce judging frequency at the time of judging whether a loop is to be repeatedly executed or not and to improve the execution performance of a program by executing loop development as for as possible even when the loop is branched from the inside to the outside. CONSTITUTION:A compiler front-ent 2 inputs a source program 1 and outputs an intermediate code 3. An optimizing phase 4 inputs an intermediate code 3 and prepares a flow graph 5, a label table 9 and loop counter information 10. A loop analyzing means 6 in the phase 4 analyzes the flow graph 5 and detects a loop having its branch on the outside of the loop. A loop development judging means 7 in the phase 4 judges the existence of a side effect that the number of reference blocks is increased or compiling time is influenced at the time of practically developing a block 2 out of the loop detected by the means 6 and determines the number of developments. When there are many reference blocks in a procedure, the loop is not developed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optimizing method for a compiler system, and more particularly to an unrolling method for a loop having a loop outside branch by an intermediate code.

[0002]

2. Description of the Related Art In the conventional optimization processing method of a compiler system, loop unrolling is performed only for a loop having no branch from inside the loop to outside the loop.

[0003]

In the above-described conventional loop unrolling method, loop unrolling is not performed when there is a branch from inside the loop to outside the loop. Therefore, if the branch outside the loop is not jumped at the time of execution, the loop is repeated. There is a drawback in that it takes time to execute the part for determining whether or not.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a loop unrolling method having an out-of-loop branch that performs loop unrolling as much as possible even when there is a branch from inside the loop to outside the loop in order to solve the above-mentioned drawbacks. .

[0005]

A loop unrolling method having an out-of-loop branch of the present invention is created based on the input intermediate code in the optimization phase of the compiler system using the intermediate code as input information. Whether or not loop unrolling is possible by analyzing the flow graph to find a loop with a branch outside the loop, and the degree of influence on the compiler time when loop unrolling the loop found by this loop analyzer And the existing label of the branch destination of the jump instruction in the basic block generated as a result of the expansion of the loop that can be expanded by this loop expansion determination means. Avoid the loop table to update the label table and guarantee the value of the loop counter at the time of branching out of the loop. Store data information, and by having a loop unrolling execution means for performing loop unrolling on the basis of the label table and the loop counter information.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.
In the embodiment shown in FIG. 1, the source program 1 and the source program 1
A compiler front end 2 for translating the intermediate code 3, an intermediate code 3 output from the compiler front end 2, a flow graph 5 created by inputting the intermediate code 3, and a jump instruction in a basic block generated as a result of expansion. By analyzing the label table 9 that stores information for avoiding duplication of the label that is the jump destination and the existing label, the loop counter information 10 that holds the information of the variable that becomes the loop counter, and the flow graph 5, Even if there is a branch outside the loop, the loop analysis means for finding the loop to be the target of the loop expansion 6, the loop expansion determination means 7 for determining whether the loop to be the target of the loop expansion is enabled or disabled, and the actual An optimization phase 4 having a loop unrolling execution means 8 for unrolling loops, The intermediate code 11 after the optimization is the output of FIG. 4, enter the intermediate code 11 objects 1
3 and a code generation phase 12 for creating the code No.3.

Next, the operation of the loop unrolling system having the branch outside the loop of the present embodiment configured as described above will be described. The compiler front end 2 inputs the source program 1 and outputs intermediate code 3. In the optimization phase 4, first, the intermediate code 3 is input, and the flow graph 5, the label table 9, and the loop counter information 10 are created. FIG. 4 shows the intermediate code 3 input in the optimization phase 4.
It is a figure which shows an example of the label table 9 made from.
In the optimization phase 4, a label table is created by newly adding a table to left for a label larger than the branch destination label appearing at the beginning of the intermediate code 3 and right for a smaller label.

The loop analysis means 6 in the optimization phase 4 analyzes the flow graph 5 and finds a loop having a branch outside the loop. FIG. 2 is a diagram showing an example of a flow graph before expansion. In Figure 2, block1 to block
k5 indicates a basic block, and the loop is block2, b
It is composed of lock4. Further, in this example, the loop unrolling determination condition checked by the loop analysis means 6 is a) block.
This is a case where the destination of the second conditional branch is block4, the destination of the b) block4 conditional branch is block2, and the immediately preceding branch block of the c) block2 satisfies block4.

The loop unrolling decision means 7 in the optimization phase 4 is bl among the loops found by the loop analysis means 6.
The number of basic blocks is increased when ock2 is actually expanded, and the number of expansions is determined by determining whether or not there is a side effect of affecting the compile time. In addition,
When it is determined that there is no side effect, the number of expansions is set to 4 in the embodiment, but when the number of basic blocks in the procedure is large, the expansion of the loop is not performed.

When the loop unrolling execution means 8 in the optimization phase 4 unrolls the loop, the chain of lefts in the label table 9 is followed and there is no branch destination (n
il), update the label table by adding to it a table with a label one greater than the previous table. In the optimization phase 4, the loop counter information 10 stores the information of the variable that becomes the loop counter.

The loop unrolling execution means 8 unrolls block 2 into four stages based on the label table 9 and the loop counter information 10. FIG. 3 shows loop unrolling execution means 8
It is a figure which shows the image of the flow graph updated by. Here, it has a label different from block2,
By adding three basic blocks that increase the loop counter by 1, the loop is expanded into four stages.

In the optimization phase 4, after performing various optimizations, the updated flow graph is analyzed and the optimized intermediate code 11 is output. Finally, the intermediate code after optimization 1
1 is input to the code generation phase 12 and the object 13
To create.

[0014]

As described above, according to the present invention, even if there is a branch outside the loop, the loop expansion can be performed, so that the number of times of determining whether or not to repeat the loop at the time of execution is reduced. It has the effect of improving performance.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a flow graph before expansion in FIG.

FIG. 3 is a diagram showing an example of a flow graph after expansion in FIG.

FIG. 4 is a diagram showing an example of a label table of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 source program 2 compiler front end 3 intermediate code 4 optimization phase 5 flow graph 6 loop analysis means 7 loop unrolling determination means 8 loop unrolling execution means 9 label table 10 loop counter information 11 intermediate code after optimization 12 code generation phase 13 Object file

Claims (1)

[Claims] 1. A loop analyzing means for finding a loop having a branch outside the loop by analyzing a flow graph created based on the input intermediate code in an optimization phase of a compiler system using the intermediate code as input information. And a loop unrolling determination unit that determines whether loop unrolling is possible by determining the degree of influence on the compiler time when the loop found by this loop analysis unit is loop unrolled,
The label table is updated by avoiding the overlap with the existing label of the branch destination of the jump instruction in the basic block generated as a result of unrolling the loop that can be loop unrolled by the loop unrolling determination means, A loop unrolling execution means for storing loop counter information for guaranteeing the value of the loop counter at the time of branching out, and for unrolling the loop based on the label table and the loop counter information. A loop unrolling method that has a branch outside the loop.