From e13ab2a9a1b8f53c46f3bbc44b012ad111b57ea9 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 5 Dec 2006 01:26:29 +0000 Subject: [PATCH] add an instcombine xform. This speeds up 462.libquantum from 9.78s to 7.48s. This regression is due to unforseen consequences of the cast patch. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32209 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/InstructionCombining.cpp | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index fac659f39b8..b12c6b58414 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -6023,6 +6023,23 @@ Instruction *InstCombiner::visitTrunc(CastInst &CI) { Value *V = InsertCastBefore(SrcI->getOperand(0), Ty, CI); return new ShiftInst(Instruction::LShr, V, SrcI->getOperand(1)); } + } else { // This is a variable shr. + + // Turn 'trunc (lshr X, Y) to bool' into '(X & (1 << Y)) != 0'. This is + // more LLVM instructions, but allows '1 << Y' to be hoisted if + // loop-invariant and CSE'd. + if (CI.getType() == Type::BoolTy && SrcI->hasOneUse()) { + Value *One = ConstantInt::get(SrcI->getType(), 1); + + Value *V = InsertNewInstBefore(new ShiftInst(Instruction::Shl, One, + SrcI->getOperand(1), + "tmp"), CI); + V = InsertNewInstBefore(BinaryOperator::createAnd(V, + SrcI->getOperand(0), + "tmp"), CI); + Value *Zero = Constant::getNullValue(V->getType()); + return BinaryOperator::createSetNE(V, Zero); + } } break; }