https://bugs.llvm.org/show_bug.cgi?id=39597
Bug ID: 39597
Summary: vectorization differences
Product: libraries
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: Loop Optimizer
Assignee: unassignedb...@nondot.org
Reporter: tras...@gmail.com
CC: llvm-bugs@lists.llvm.org
void foo(unsigned* x)
{
for (int i = 0; i < 8; ++i)
x[i] = (x[i] % 3 == 0) ? 0 : x[i];
}
void bar(unsigned* x)
{
for (int i = 0; i < 8; ++i)
if (x[i] % 3 == 0)
x[i] = 0;
}
$ clang -O3 -march=haswell -Rpass="loop|vect" -Rpass-missed="loop|vect"
-Rpass-analysis="loop|vect"
<source>:3:5: remark: completely unrolled loop with 8 iterations
[-Rpass=loop-unroll]
<source>:9:5: remark: completely unrolled loop with 8 iterations
[-Rpass=loop-unroll]
<source>:4:18: remark: Stores SLP vectorized with cost -17 and with tree size 8
[-Rpass=slp-vectorizer]
$ clang -O3 -fno-unroll-loops -march=haswell -Rpass="loop|vect"
-Rpass-missed="loop|vect" -Rpass-analysis="loop|vect"
<source>:3:5: remark: vectorized loop (vectorization width: 8, interleaved
count: 1) [-Rpass=loop-vectorize]
<source>:9:5: remark: vectorized loop (vectorization width: 8, interleaved
count: 1) [-Rpass=loop-vectorize]
The generated code is different in all 4 cases:
https://godbolt.org/z/7EaJfc
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