InstCombine: Also turn selects fed by an and into arithmetic when the types don't match.
Inserting a zext or trunc is sufficient. This pattern is somewhat common in
LLVM's pointer mangling code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185270 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 59502fb..7581dbe 100644
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -662,7 +662,7 @@
ConstantInt *FalseVal,
InstCombiner::BuilderTy *Builder) {
const ICmpInst *IC = dyn_cast<ICmpInst>(SI.getCondition());
- if (!IC || !IC->isEquality())
+ if (!IC || !IC->isEquality() || !SI.getType()->isIntegerTy())
return 0;
if (!match(IC->getOperand(1), m_Zero()))
@@ -670,8 +670,7 @@
ConstantInt *AndRHS;
Value *LHS = IC->getOperand(0);
- if (LHS->getType() != SI.getType() ||
- !match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
+ if (!match(LHS, m_And(m_Value(), m_ConstantInt(AndRHS))))
return 0;
// If both select arms are non-zero see if we have a select of the form
@@ -705,7 +704,13 @@
unsigned ValZeros = ValC->getValue().logBase2();
unsigned AndZeros = AndRHS->getValue().logBase2();
- Value *V = LHS;
+ // If types don't match we can still convert the select by introducing a zext
+ // or a trunc of the 'and'. The trunc case requires that all of the truncated
+ // bits are zero, we can figure that out by looking at the 'and' mask.
+ if (AndZeros >= ValC->getBitWidth())
+ return 0;
+
+ Value *V = Builder->CreateZExtOrTrunc(LHS, SI.getType());
if (ValZeros > AndZeros)
V = Builder->CreateShl(V, ValZeros - AndZeros);
else if (ValZeros < AndZeros)