diff options
Diffstat (limited to 'llvm')
| -rw-r--r-- | llvm/lib/Transforms/Scalar/InstructionCombining.cpp | 32 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/2009-12-17-CmpSelectNull.ll | 16 |
2 files changed, 33 insertions, 15 deletions
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp index 2a82e0f2335..a6e0eef854d 100644 --- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp @@ -6356,24 +6356,26 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) { // comparison into the select arms, which will cause one to be // constant folded and the select turned into a bitwise or. Value *Op1 = 0, *Op2 = 0; - if (LHSI->hasOneUse()) { - if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) { - // Fold the known value into the constant operand. - Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); - // Insert a new ICmp of the other select operand. - Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), - RHSC, I.getName()); - } else if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) { - // Fold the known value into the constant operand. - Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); - // Insert a new ICmp of the other select operand. + if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(1))) + Op1 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); + if (Constant *C = dyn_cast<Constant>(LHSI->getOperand(2))) + Op2 = ConstantExpr::getICmp(I.getPredicate(), C, RHSC); + + // We only want to perform this transformation if it will not lead to + // additional code. This is true if either both sides of the select + // fold to a constant (in which case the icmp is replaced with a select + // which will usually simplify) or this is the only user of the + // select (in which case we are trading a select+icmp for a simpler + // select+icmp). + if ((Op1 && Op2) || (LHSI->hasOneUse() && (Op1 || Op2))) { + if (!Op1) Op1 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(1), RHSC, I.getName()); - } - } - - if (Op1) + if (!Op2) + Op2 = Builder->CreateICmp(I.getPredicate(), LHSI->getOperand(2), + RHSC, I.getName()); return SelectInst::Create(LHSI->getOperand(0), Op1, Op2); + } break; } case Instruction::Call: diff --git a/llvm/test/Transforms/InstCombine/2009-12-17-CmpSelectNull.ll b/llvm/test/Transforms/InstCombine/2009-12-17-CmpSelectNull.ll new file mode 100644 index 00000000000..fb7497b395d --- /dev/null +++ b/llvm/test/Transforms/InstCombine/2009-12-17-CmpSelectNull.ll @@ -0,0 +1,16 @@ +; RUN: opt < %s -instcombine -S | FileCheck %s + +@.str254 = internal constant [2 x i8] c".\00" +@.str557 = internal constant [3 x i8] c"::\00" + +define i8* @demangle_qualified(i32 %isfuncname) nounwind { +entry: + %tobool272 = icmp ne i32 %isfuncname, 0 + %cond276 = select i1 %tobool272, i8* getelementptr inbounds ([2 x i8]* @.str254, i32 0, i32 0), i8* getelementptr inbounds ([3 x i8]* @.str557, i32 0, i32 0) ; <i8*> [#uses=4] + %cmp.i504 = icmp eq i8* %cond276, null + %rval = getelementptr i8* %cond276, i1 %cmp.i504 + ret i8* %rval +} + +; CHECK: %cond276 = select i1 +; CHECK: ret i8* %cond276 |
