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| author | Arnold Schwaighofer <aschwaighofer@apple.com> | 2013-04-12 15:15:19 +0000 |
|---|---|---|
| committer | Arnold Schwaighofer <aschwaighofer@apple.com> | 2013-04-12 15:15:19 +0000 |
| commit | 08a0e8f8dbae6314dade60e1ef92e73e89c5ff23 (patch) | |
| tree | c92a7deba86db295ab34ac2acbcd84ed94d77325 /lib/Transforms | |
| parent | b6ad2bd51195f7675db0f71c5826a12a2b7090fc (diff) | |
LoopVectorizer: integer division is not a reduction operation
Don't classify idiv/udiv as a reduction operation. Integer division is lossy.
For example : (1 / 2) * 4 != 4/2.
Example:
int a[] = { 2, 5, 2, 2}
int x = 80;
for()
x /= a[i];
Scalar:
x /= 2 // = 40
x /= 5 // = 8
x /= 2 // = 4
x /= 2 // = 2
Vectorized:
<80, 1> / <2,5> //= <40,0>
<40, 0> / <2,2> //= <20,0>
20*0 = 0
radar://13640654
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179381 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Vectorize/LoopVectorize.cpp | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index acf2b819b8..238fc8bfb7 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -2833,8 +2833,6 @@ LoopVectorizationLegality::isReductionInstr(Instruction *I, case Instruction::Sub: case Instruction::Add: return Kind == RK_IntegerAdd; - case Instruction::SDiv: - case Instruction::UDiv: case Instruction::Mul: return Kind == RK_IntegerMult; case Instruction::And: |