Simplify demanded bits of select sources where the condition is a constant vector
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160835 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 46ba83b..54be8ed 100644
--- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -989,6 +989,29 @@
}
break;
}
+ case Instruction::Select: {
+ APInt LeftDemanded(DemandedElts), RightDemanded(DemandedElts);
+ if (ConstantVector* CV = dyn_cast<ConstantVector>(I->getOperand(0))) {
+ for (unsigned i = 0; i < VWidth; i++) {
+ if (CV->getAggregateElement(i)->isNullValue())
+ LeftDemanded.clearBit(i);
+ else
+ RightDemanded.clearBit(i);
+ }
+ }
+
+ TmpV = SimplifyDemandedVectorElts(I->getOperand(1), LeftDemanded,
+ UndefElts, Depth+1);
+ if (TmpV) { I->setOperand(1, TmpV); MadeChange = true; }
+
+ TmpV = SimplifyDemandedVectorElts(I->getOperand(2), RightDemanded,
+ UndefElts2, Depth+1);
+ if (TmpV) { I->setOperand(2, TmpV); MadeChange = true; }
+
+ // Output elements are undefined if both are undefined.
+ UndefElts &= UndefElts2;
+ break;
+ }
case Instruction::BitCast: {
// Vector->vector casts only.
VectorType *VTy = dyn_cast<VectorType>(I->getOperand(0)->getType());