Canonicalize boolean +/- a constant to a select.
(I think it's reasonably clear that we want to have a canonical form for
constructs like this; if anyone thinks that a select is not the best
canonical form, please tell me.)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75531 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 5b9659e..c93994f 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -2101,13 +2101,10 @@
if (SimplifyDemandedInstructionBits(I))
return &I;
- // zext(i1) - 1 -> select i1, 0, -1
+ // zext(bool) + C -> bool ? C + 1 : C
if (ZExtInst *ZI = dyn_cast<ZExtInst>(LHS))
- if (CI->isAllOnesValue() &&
- ZI->getOperand(0)->getType() == Type::Int1Ty)
- return SelectInst::Create(ZI->getOperand(0),
- Context->getNullValue(I.getType()),
- Context->getAllOnesValue(I.getType()));
+ if (ZI->getSrcTy() == Type::Int1Ty)
+ return SelectInst::Create(ZI->getOperand(0), AddOne(CI, Context), CI);
}
if (isa<PHINode>(LHS))
@@ -2525,6 +2522,11 @@
if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
if (Instruction *R = FoldOpIntoSelect(I, SI, this))
return R;
+
+ // C - zext(bool) -> bool ? C - 1 : C
+ if (ZExtInst *ZI = dyn_cast<ZExtInst>(Op1))
+ if (ZI->getSrcTy() == Type::Int1Ty)
+ return SelectInst::Create(ZI->getOperand(0), SubOne(C, Context), C);
}
if (I.getType() == Type::Int1Ty)