diff options
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 23 | ||||
| -rw-r--r-- | test/Analysis/ScalarEvolution/xor-and.ll | 5 |
2 files changed, 22 insertions, 6 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 94fb871dc3..751a635194 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -2453,10 +2453,25 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) { LCI->getValue() == CI->getValue()) if (const SCEVZeroExtendExpr *Z = dyn_cast<SCEVZeroExtendExpr>(getSCEV(U->getOperand(0)))) { - SCEVHandle ZO = Z->getOperand(); - if (APIntOps::isMask(getTypeSizeInBits(ZO->getType()), - CI->getValue())) - return getZeroExtendExpr(getNotSCEV(ZO), U->getType()); + const Type *UTy = U->getType(); + SCEVHandle Z0 = Z->getOperand(); + const Type *Z0Ty = Z0->getType(); + unsigned Z0TySize = getTypeSizeInBits(Z0Ty); + + // If C is a low-bits mask, the zero extend is zerving to + // mask off the high bits. Complement the operand and + // re-apply the zext. + if (APIntOps::isMask(Z0TySize, CI->getValue())) + return getZeroExtendExpr(getNotSCEV(Z0), UTy); + + // If C is a single bit, it may be in the sign-bit position + // before the zero-extend. In this case, represent the xor + // using an add, which is equivalent, and re-apply the zext. + APInt Trunc = APInt(CI->getValue()).trunc(Z0TySize); + if (APInt(Trunc).zext(getTypeSizeInBits(UTy)) == CI->getValue() && + Trunc.isSignBit()) + return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)), + UTy); } } break; diff --git a/test/Analysis/ScalarEvolution/xor-and.ll b/test/Analysis/ScalarEvolution/xor-and.ll index 9b02bb803f..843052456a 100644 --- a/test/Analysis/ScalarEvolution/xor-and.ll +++ b/test/Analysis/ScalarEvolution/xor-and.ll @@ -1,6 +1,7 @@ -; RUN: llvm-as < %s | opt -scalar-evolution -disable-output -analyze | grep {\\--> %z} +; RUN: llvm-as < %s | opt -scalar-evolution -disable-output -analyze \ +; RUN: | grep {\\--> (zext i4 (-8 + (trunc i64 (8 \\* %x) to i4)) to i64)} -; ScalarEvolution shouldn't try to analyze %s into something like +; ScalarEvolution shouldn't try to analyze %z into something like ; --> (zext i4 (-1 + (-1 * (trunc i64 (8 * %x) to i4))) to i64) define i64 @foo(i64 %x) { |