diff --git a/llvm/lib/VMCore/ConstantFold.cpp b/llvm/lib/VMCore/ConstantFold.cpp index 579d356b1de2..8cca06fdda04 100644 --- a/llvm/lib/VMCore/ConstantFold.cpp +++ b/llvm/lib/VMCore/ConstantFold.cpp @@ -1014,20 +1014,38 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, case Instruction::Add: case Instruction::Sub: return UndefValue::get(C1->getType()); - case Instruction::Mul: case Instruction::And: + if (isa(C1) && isa(C2)) // undef & undef -> undef + return C1; + return Constant::getNullValue(C1->getType()); // undef & X -> 0 + case Instruction::Mul: { + ConstantInt *CI; + // X * undef -> undef if X is odd or undef + if (((CI = dyn_cast(C1)) && CI->getValue()[0]) || + ((CI = dyn_cast(C2)) && CI->getValue()[0]) || + (isa(C1) && isa(C2))) + return UndefValue::get(C1->getType()); + + // X * undef -> 0 otherwise return Constant::getNullValue(C1->getType()); + } case Instruction::UDiv: case Instruction::SDiv: + // undef / 1 -> undef + if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) + if (ConstantInt *CI2 = dyn_cast(C2)) + if (CI2->isOne()) + return C1; + // FALL THROUGH case Instruction::URem: case Instruction::SRem: if (!isa(C2)) // undef / X -> 0 return Constant::getNullValue(C1->getType()); return C2; // X / undef -> undef case Instruction::Or: // X | undef -> -1 - if (const VectorType *PTy = dyn_cast(C1->getType())) - return Constant::getAllOnesValue(PTy); - return Constant::getAllOnesValue(C1->getType()); + if (isa(C1) && isa(C2)) // undef | undef -> undef + return C1; + return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 case Instruction::LShr: if (isa(C2) && isa(C1)) return C1; // undef lshr undef -> undef @@ -1041,6 +1059,8 @@ Constant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, else return C1; // X ashr undef --> X case Instruction::Shl: + if (isa(C2) && isa(C1)) + return C1; // undef shl undef -> undef // undef << X -> 0 or X << undef -> 0 return Constant::getNullValue(C1->getType()); } diff --git a/llvm/test/Transforms/InstSimplify/binop.ll b/llvm/test/Transforms/InstSimplify/binop.ll new file mode 100644 index 000000000000..f4bc55753a58 --- /dev/null +++ b/llvm/test/Transforms/InstSimplify/binop.ll @@ -0,0 +1,99 @@ +; RUN: opt -instsimplify -S < %s | FileCheck %s + +; @test0 +; CHECK: ret i64 undef +define i64 @test0() { + %r = mul i64 undef, undef + ret i64 %r +} + +; @test1 +; CHECK: ret i64 undef +define i64 @test1() { + %r = mul i64 3, undef + ret i64 %r +} + +; @test2 +; CHECK: ret i64 undef +define i64 @test2() { + %r = mul i64 undef, 3 + ret i64 %r +} + +; @test3 +; CHECK: ret i64 0 +define i64 @test3() { + %r = mul i64 undef, 6 + ret i64 %r +} + +; @test4 +; CHECK: ret i64 0 +define i64 @test4() { + %r = mul i64 6, undef + ret i64 %r +} + +; @test5 +; CHECK: ret i64 undef +define i64 @test5() { + %r = and i64 undef, undef + ret i64 %r +} + +; @test6 +; CHECK: ret i64 undef +define i64 @test6() { + %r = or i64 undef, undef + ret i64 %r +} + +; @test7 +; CHECK: ret i64 undef +define i64 @test7() { + %r = udiv i64 undef, 1 + ret i64 %r +} + +; @test8 +; CHECK: ret i64 undef +define i64 @test8() { + %r = sdiv i64 undef, 1 + ret i64 %r +} + +; @test9 +; CHECK: ret i64 0 +define i64 @test9() { + %r = urem i64 undef, 1 + ret i64 %r +} + +; @test10 +; CHECK: ret i64 0 +define i64 @test10() { + %r = srem i64 undef, 1 + ret i64 %r +} + +; @test11 +; CHECK: ret i64 undef +define i64 @test11() { + %r = shl i64 undef, undef + ret i64 %r +} + +; @test12 +; CHECK: ret i64 undef +define i64 @test12() { + %r = ashr i64 undef, undef + ret i64 %r +} + +; @test13 +; CHECK: ret i64 undef +define i64 @test13() { + %r = lshr i64 undef, undef + ret i64 %r +}