diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Target/README.txt | 5 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 23 |
2 files changed, 16 insertions, 12 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index fcec368a21..4e382e8f8e 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -870,11 +870,6 @@ rshift_gt (unsigned int a) bar (); } -void neg_eq_cst(unsigned int a) { -if (-a == 123) -bar(); -} - All should simplify to a single comparison. All of these are currently not optimized with "clang -emit-llvm-bc | opt -std-compile-opts". diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 5ddf23ba8e..42db444ff6 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1407,18 +1407,27 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, case Instruction::Xor: // For the xor case, we can xor two constants together, eliminating // the explicit xor. - if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) - return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + if (Constant *BOC = dyn_cast<Constant>(BO->getOperand(1))) { + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), ConstantExpr::getXor(RHS, BOC)); - - // FALLTHROUGH + } else if (RHSV == 0) { + // Replace ((xor A, B) != 0) with (A != B) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), + BO->getOperand(1)); + } + break; case Instruction::Sub: - // Replace (([sub|xor] A, B) != 0) with (A != B) - if (RHSV == 0) + // Replace ((sub A, B) != C) with (B != A-C) if A & C are constants. + if (ConstantInt *BOp0C = dyn_cast<ConstantInt>(BO->getOperand(0))) { + if (BO->hasOneUse()) + return new ICmpInst(ICI.getPredicate(), BO->getOperand(1), + ConstantExpr::getSub(BOp0C, RHS)); + } else if (RHSV == 0) { + // Replace ((sub A, B) != 0) with (A != B) return new ICmpInst(ICI.getPredicate(), BO->getOperand(0), BO->getOperand(1)); + } break; - case Instruction::Or: // If bits are being or'd in that are not present in the constant we // are comparing against, then the comparison could never succeed! |