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InstCombine now optimizes vector udiv by power of 2 to shifts

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Fixes r8429


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144036 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Pete Cooper
2011-11-07 23:04:49 +00:00
parent 1b4f6f2532
commit a29fc806fe
2 changed files with 24 additions and 5 deletions
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lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+9 -5
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@@ -441,19 +441,23 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
// Handle the integer div common cases
if (Instruction *Common = commonIDivTransforms(I))
return Common;
if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
{
// X udiv 2^C -> X >> C
// Check to see if this is an unsigned division with an exact power of 2,
// if so, convert to a right shift.
if (C->getValue().isPowerOf2()) { // 0 not included in isPowerOf2
const APInt *C;
if (match(Op1, m_Power2(C))) {
BinaryOperator *LShr =
BinaryOperator::CreateLShr(Op0,
ConstantInt::get(Op0->getType(), C->getValue().logBase2()));
BinaryOperator::CreateLShr(Op0,
ConstantInt::get(Op0->getType(),
C->logBase2()));
if (I.isExact()) LShr->setIsExact();
return LShr;
}
}
if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
// X udiv C, where C >= signbit
if (C->getValue().isNegative()) {
Value *IC = Builder->CreateICmpULT(Op0, C);