[InstCombine] Catch more bswap cases missed due to zext and truncs.
Fixes PR27824.
Differential Revision: http://reviews.llvm.org/D20591.
llvm-svn: 270853
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index a536ddc..edde166 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1773,7 +1773,23 @@
// If the AndMask is zero for this bit, clear the bit.
if ((AndMask & Bit) == 0)
Result->Provenance[i] = BitPart::Unset;
+ return Result;
+ }
+ // If this is a zext instruction zero extend the result.
+ if (I->getOpcode() == Instruction::ZExt) {
+ auto &Res = collectBitParts(I->getOperand(0), MatchBSwaps,
+ MatchBitReversals, BPS);
+ if (!Res)
+ return Result;
+
+ Result = BitPart(Res->Provider, BitWidth);
+ auto NarrowBitWidth =
+ cast<IntegerType>(cast<ZExtInst>(I)->getSrcTy())->getBitWidth();
+ for (unsigned i = 0; i < NarrowBitWidth; ++i)
+ Result->Provenance[i] = Res->Provenance[i];
+ for (unsigned i = NarrowBitWidth; i < BitWidth; ++i)
+ Result->Provenance[i] = BitPart::Unset;
return Result;
}
}
@@ -1816,6 +1832,15 @@
return false; // Can't do vectors or integers > 128 bits.
unsigned BW = ITy->getBitWidth();
+ unsigned DemandedBW = BW;
+ IntegerType *DemandedTy = ITy;
+ if (I->hasOneUse()) {
+ if (TruncInst *Trunc = dyn_cast<TruncInst>(I->user_back())) {
+ DemandedTy = cast<IntegerType>(Trunc->getType());
+ DemandedBW = DemandedTy->getBitWidth();
+ }
+ }
+
// Try to find all the pieces corresponding to the bswap.
std::map<Value *, Optional<BitPart>> BPS;
auto Res = collectBitParts(I, MatchBSwaps, MatchBitReversals, BPS);
@@ -1825,11 +1850,12 @@
// Now, is the bit permutation correct for a bswap or a bitreverse? We can
// only byteswap values with an even number of bytes.
- bool OKForBSwap = BW % 16 == 0, OKForBitReverse = true;
- for (unsigned i = 0; i < BW; ++i) {
- OKForBSwap &= bitTransformIsCorrectForBSwap(BitProvenance[i], i, BW);
+ bool OKForBSwap = DemandedBW % 16 == 0, OKForBitReverse = true;
+ for (unsigned i = 0; i < DemandedBW; ++i) {
+ OKForBSwap &=
+ bitTransformIsCorrectForBSwap(BitProvenance[i], i, DemandedBW);
OKForBitReverse &=
- bitTransformIsCorrectForBitReverse(BitProvenance[i], i, BW);
+ bitTransformIsCorrectForBitReverse(BitProvenance[i], i, DemandedBW);
}
Intrinsic::ID Intrin;
@@ -1840,6 +1866,24 @@
else
return false;
+ if (ITy != DemandedTy) {
+ Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, DemandedTy);
+ Value *Provider = Res->Provider;
+ IntegerType *ProviderTy = cast<IntegerType>(Provider->getType());
+ // We may need to truncate the provider.
+ if (DemandedTy != ProviderTy) {
+ auto *Trunc = CastInst::Create(Instruction::Trunc, Provider, DemandedTy,
+ "trunc", I);
+ InsertedInsts.push_back(Trunc);
+ Provider = Trunc;
+ }
+ auto *CI = CallInst::Create(F, Provider, "rev", I);
+ InsertedInsts.push_back(CI);
+ auto *ExtInst = CastInst::Create(Instruction::ZExt, CI, ITy, "zext", I);
+ InsertedInsts.push_back(ExtInst);
+ return true;
+ }
+
Function *F = Intrinsic::getDeclaration(I->getModule(), Intrin, ITy);
InsertedInsts.push_back(CallInst::Create(F, Res->Provider, "rev", I));
return true;