https://llvm.org/bugs/show_bug.cgi?id=25793
Bug ID: 25793
Summary: [polly] The order of the loop is reversed while not
necessary
Product: tools
Version: trunk
Hardware: PC
OS: Windows NT
Status: NEW
Severity: normal
Priority: P
Component: opt
Assignee: unassignedb...@nondot.org
Reporter: lawre...@codeaurora.org
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 15426
--> https://llvm.org/bugs/attachment.cgi?id=15426&action=edit
reduced testcase
Polly schedule changed the order of the loop unnecessaryly.
Here is the original order of the loop in c:
void foo (int * restrict A, int * restrict B, int * restrict C, int n) {
for(int i = 0; i < n; i++)
A[i] += 1;
for(int i = 0; i < n; i++)
B[i] += 1;
for(int i = 0; i < n; i++)
C[i] += 1;
}
Polly schedule reorder the loops to:
void foo (int * restrict A, int * restrict B, int * restrict C, int n) {
for(int i = 0; i < n; i++)
C[i] += 1;
for(int i = 0; i < n; i++)
A[i] += 1;
for(int i = 0; i < n; i++)
B[i] += 1;
}
Here is the isl ast for attached IR
{
#pragma simd
#pragma known-parallel
for (int c0 = 0; c0 < n; c0 += 1)
Stmt_for_body16(c0);
#pragma simd
#pragma known-parallel
for (int c0 = 0; c0 < n; c0 += 1)
Stmt_for_body(c0);
#pragma simd
#pragma known-parallel
for (int c0 = 0; c0 < n; c0 += 1)
Stmt_for_body5(c0);
}
Even though it is logically correct, however it is not necessary, and afffect
readability.
Use opt -debug -polly -polly-detect -polly-opt-isl -polly-codegen
-polly-vectorizer=polly -polly-ignore-aliasing -S <t.ll >log.log 2>&1 to
reproduce it
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