Compiler optimizations for vector operations that are reformatting-resistant

Patent metadata

Field	Value
Publication number	US-9880821-B2
Application number	US-201514827639-A
Country	US
Kind code	B2
Filing date	Aug 17, 2015
Priority date	Aug 17, 2015
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

An optimizing compiler includes a vector optimization mechanism that optimizes vector operations that are reformatting-resistant, such as source instructions that do not have a corresponding reformatting operation, sink instructions that do not have a corresponding reformatting operation, a source instruction that is a scalar value, a sink instruction that may produce a scalar value, and an internal operation that depends on lanes being in a specified order. The ability to optimize vector instructions that are reformatting-resistant reduces the number of operations to improve the run-time performance of the code.

First claim

The invention claimed is:

1. A computer-implemented method executed by at least one processor for processing a plurality of instructions in a computer program, the method comprising:
providing a computer program including a plurality of instructions that includes at least one vector operation and that includes a plurality of reformatting-resistant vector operations, wherein the plurality of formatting-resistant vector operations includes a source instruction without a corresponding reformatting operation; and
optimizing at least one of the plurality of reformatting-resistant vector operations in the computer program to enhance run-time performance of the computer program.

2. The method of claim 1 wherein the plurality of reformatting-resistant vector operations comprises a sink instruction without a corresponding reformatting operation.

3. The method of claim 1 wherein the plurality of reformatting-resistant vector operations comprises a source instruction that operates on a scalar value.

4. The method of claim 1 wherein the plurality of reformatting-resistant vector operations comprises a sink instruction that can produce a scalar value.

5. The method of claim 1 wherein the plurality of reformatting-resistant vector operations comprises an internal operation that depends on lanes being in a specified order.

6. The method of claim 1 further comprising analyzing an existing code portion in the computer program, determining a proposed change to the existing code portion in the computer program, and when the proposed change to the existing code portion has a cost less than a cost of the existing code portion, modifying the existing code portion with the proposed change.

7. The method of claim 1 wherein the step of optimizing the at least one reformatting-resistant operation in the computer program comprises:
(a) finding all data flow subgraphs in the computer program;
(b) identifying source instructions, sink instructions, and internal instructions that are reformatting-resistant;
(c) selecting a data flow subgraph;
(d) determining a preferred vector element order;
(e) determining a savings of removing reformatting instructions from source instructions and sink instructions that have the reformatting instructions;
(f) determining a cost of inserting reformatting and other adjustment instructions at sources, sinks and internal instructions that are reformatting-resistant;
(g) when the savings minus the cost is not negative, removing the reformatting instructions from source instructions and sink instructions that have the reformatting instructions, and inserting the reformatting and other adjustment instructions; and
(h) when there are more data flow subgraphs to process, return to step (c) and continue processing until there are no more data flow subgraphs to process.

8. The method of claim 1 wherein the at least one reformatting-resistant instruction is selected from the group comprising:
a source instruction without a corresponding reformatting operation;
a sink instruction without a corresponding reformatting operation;
a source instruction that operates on a scalar value;
a sink instruction that can produce a scalar value; and
an internal operation that depends on lanes being in a specified order.

9. A computer-implemented method executed by at least one processor for processing a plurality of instructions in a computer program, the method comprising:
(a) providing a computer program including a plurality of instructions that includes at least one vector instruction;
(b) finding all data flow subgraphs in the computer program;
(c) identifying source instructions, sink instructions, and internal instructions that are reformatting-resistant comprising:
a source instruction without a corresponding reformatting operation;
a sink instruction without a corresponding reformatting operation;
a source instruction that operates on a scalar value;
a sink instruction that can produce a scalar value; and
an internal operation that depends on lanes being in a specified order;

(d) selecting a data flow subgraph;
(e) determining a preferred vector element order;
(f) determining a savings of removing reformatting instructions from source instructions and sink instructions that have the reformatting instructions;
(g) determining a cost of inserting reformatting and other adjustment instructions at sources, sinks and internal instructions that are reformatting-resistant;
(h) when the savings minus the cost is not negative, removing the reformatting instructions from source instructions and sink instructions that have the reformatting instructions, and inserting the reformatting and other adjustment instructions; and
(i) when there are more data flow subgraphs to process, return to step (d) and continue processing until there are no more data flow subgraphs to process.

Assignees

• IBM

Inventors

• Gschwind Michael Karl
• Schmidt William J

Classifications

• G06F8/4441 Primary

  Reducing the execution time required by the program code · CPC title