From f63f647345d0305685e837ad7d89181ea643c2e2 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Mon, 27 Sep 2004 16:18:50 +0000 Subject: [PATCH] Fold: (setcc (shr X, ShAmt), CI), where 'cc' is eq or ne. This xform triggers often, for example: 6x in povray, 1x in gzip, 279x in gcc, 1x in crafty, 8x in eon, 11x in perlbmk, 362x in gap, 4x in vortex, 14 in m88ksim, 211x in 126.gcc, 1x in compress, 11x in ijpeg, and 4x in 147.vortex. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@16521 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/InstructionCombining.cpp | 45 ++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index e579cf1a7bc..cdfdc34555b 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -1545,6 +1545,51 @@ Instruction *InstCombiner::visitSetCondInst(BinaryOperator &I) { } } break; + case Instruction::Shr: // shr: (setcc (shr X, ShAmt), CI) + if (ConstantUInt *ShAmt = dyn_cast(LHSI->getOperand(1))) { + unsigned ShAmtVal = ShAmt->getValue(); + + switch (I.getOpcode()) { + default: break; + case Instruction::SetEQ: + case Instruction::SetNE: { + // If we are comparing against bits always shifted out, the + // comparison cannot succeed. + Constant *Comp = + ConstantExpr::getShr(ConstantExpr::getShl(CI, ShAmt), ShAmt); + + if (Comp != CI) {// Comparing against a bit that we know is zero. + bool IsSetNE = I.getOpcode() == Instruction::SetNE; + Constant *Cst = ConstantBool::get(IsSetNE); + return ReplaceInstUsesWith(I, Cst); + } + + if (LHSI->hasOneUse() || CI->isNullValue()) { + // Otherwise strength reduce the shift into an and. + uint64_t Val = ~0ULL; // All ones. + Val <<= ShAmtVal; // Shift over to the right spot. + + Constant *Mask; + if (CI->getType()->isUnsigned()) { + unsigned TypeBits = CI->getType()->getPrimitiveSize()*8; + Val &= (1ULL << TypeBits)-1; + Mask = ConstantUInt::get(CI->getType(), Val); + } else { + Mask = ConstantSInt::get(CI->getType(), Val); + } + + Instruction *AndI = + BinaryOperator::createAnd(LHSI->getOperand(0), + Mask, LHSI->getName()+".mask"); + Value *And = InsertNewInstBefore(AndI, I); + return new SetCondInst(I.getOpcode(), And, + ConstantExpr::getShl(CI, ShAmt)); + } + break; + } + } + } + break; case Instruction::Div: if (0 && isa(LHSI->getOperand(1))) { -- 2.11.0