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When turning (ashr(shl(x, n), n)) into sext(trunc(x)), the width of the

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type to truncate to should be the number of bits of the value that are
preserved, not the number that are clobbered with sign-extension.
This fixes regressions in ldecod.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@69704 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2009-04-21 20:18:36 +00:00
parent 4558f481b8
commit 578ccf81e5
2 changed files with 30 additions and 1 deletions
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2
lib/Analysis/ScalarEvolution.cpp
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@ -2015,7 +2015,7 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
if (L->getOpcode() == Instruction::Shl &&
L->getOperand(1) == U->getOperand(1)) {
uint64_t Amt = CI->getZExtValue();
uint64_t Amt = getTypeSizeInBits(U->getType()) - CI->getZExtValue();
return
SE.getSignExtendExpr(SE.getTruncateExpr(getSCEV(L->getOperand(0)),
IntegerType::get(Amt)),