Implement InstCombine/add.ll:test17 & 18
llvm-svn: 8817
diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index e69db1d..465954a 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -437,6 +437,22 @@
if (Constant *C2 = dyn_castMaskingAnd(RHS))
if (Instruction *R = AssociativeOpt(I, AddMaskingAnd(C2))) return R;
+ if (ConstantInt *CRHS = dyn_cast<ConstantInt>(RHS)) {
+ if (Instruction *ILHS = dyn_cast<Instruction>(LHS)) {
+ switch (ILHS->getOpcode()) {
+ case Instruction::Xor:
+ // ~X + C --> (C-1) - X
+ if (ConstantInt *XorRHS = dyn_cast<ConstantInt>(ILHS->getOperand(1)))
+ if (XorRHS->isAllOnesValue())
+ return BinaryOperator::create(Instruction::Sub,
+ *CRHS - *ConstantInt::get(I.getType(), 1),
+ ILHS->getOperand(0));
+ break;
+ default: break;
+ }
+ }
+ }
+
return Changed ? &I : 0;
}