[LLVMdev] [Loop Vectorize] Question on -O3
maxs
xtxwy.ustc at gmail.com
Tue Jul 2 00:49:49 PDT 2013
Hi,
When I use "-loop-vectorize" to vectorize a loop as below:
//====================================
void bar(float *A, float* B, float K, int start, int end) {
for (int i = start; i < end; ++i)
A[i] *= B[i] + K;
}
//====================================
First, I use "*clang -O0 -emit-llvm -S bar.c -o bar.l*" to emit the
.l file.
Then I use "*opt -loop-vectorize -S bar.l -o bar.v.l*".
Unfortunately, the vectorization don't work. But I use "*opt -O3
-loop-vectorize -S bar.l -o bar.v.l*" and it works.
My question is: What the information needed by "*-loop-vectorize*"
the "*-O3*" provides? Thanks.
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