From ed1d8bb18a96d40ee22fc9759c0c4388519d0011 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Thu, 18 Jun 2009 00:00:20 +0000 Subject: Teach ScalarEvolution how to recognize another xor(and(x, C), C) case. If C is a single bit and the and gets analyzed as a truncate and zero-extend, the xor can be represnted as an add. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73664 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) (limited to 'lib/Analysis') diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index 94fb871..751a635 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(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; -- cgit v1.1