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| author | David Majnemer <david.majnemer@gmail.com> | 2016-07-25 03:39:21 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2016-07-25 03:39:21 +0000 |
| commit | 126de5d4b45d9fa2c55eaba761103cccd3113468 (patch) | |
| tree | 014bdaf93764ef02bfe542f25f0040a76f320bea /llvm/lib/Analysis/InstructionSimplify.cpp | |
| parent | aedcbf898b7136b3aa09f236240eb5f1f05e4b78 (diff) | |
| download | llvm-126de5d4b45d9fa2c55eaba761103cccd3113468.zip llvm-126de5d4b45d9fa2c55eaba761103cccd3113468.tar.gz llvm-126de5d4b45d9fa2c55eaba761103cccd3113468.tar.bz2 | |
[InstSimplify] Fold trunc([zs]ext(%V)) -> %V
Truncates can completely cancel out a zext or sext instruction.
llvm-svn: 276604
Diffstat (limited to 'llvm/lib/Analysis/InstructionSimplify.cpp')
| -rw-r--r-- | llvm/lib/Analysis/InstructionSimplify.cpp | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp index c7e1724..981fb97 100644 --- a/llvm/lib/Analysis/InstructionSimplify.cpp +++ b/llvm/lib/Analysis/InstructionSimplify.cpp @@ -3790,9 +3790,15 @@ static Value *SimplifyPHINode(PHINode *PN, const Query &Q) { } static Value *SimplifyTruncInst(Value *Op, Type *Ty, const Query &Q, unsigned) { - if (Constant *C = dyn_cast<Constant>(Op)) + if (auto *C = dyn_cast<Constant>(Op)) return ConstantFoldCastOperand(Instruction::Trunc, C, Ty, Q.DL); + // trunc([zs]ext(x)) -> x if the trunc undoes the work of the [zs]ext. + if (auto *CI = dyn_cast<CastInst>(Op)) + if (isa<ZExtInst>(CI) || isa<SExtInst>(CI)) + if (CI->getOperand(0)->getType() == Ty) + return CI->getOperand(0); + return nullptr; } |