diff options
| -rw-r--r-- | lib/Target/README.txt | 5 | ||||
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineCompares.cpp | 23 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/icmp.ll | 16 |
3 files changed, 32 insertions, 12 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index fcec368..4e382e8 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 5ddf23b..42db444 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! diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index ecbba23..c8f7f81 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -531,3 +531,19 @@ define i1 @test54(i8 %a) nounwind { %ret = icmp eq i32 %and, 128 ret i1 %ret } + +; CHECK: @test55 +; CHECK-NEXT: icmp eq i32 %a, -123 +define i1 @test55(i32 %a) { + %sub = sub i32 0, %a + %cmp = icmp eq i32 %sub, 123 + ret i1 %cmp +} + +; CHECK: @test56 +; CHECK-NEXT: icmp eq i32 %a, -113 +define i1 @test56(i32 %a) { + %sub = sub i32 10, %a + %cmp = icmp eq i32 %sub, 123 + ret i1 %cmp +} |