[CodeGenPrep] Handle constants in ConvertPhiType

This is a simple addition to the convertPhiTypes in CodeGenPrepare to
consider and convert constants as it converts the phi type. Someone
fixed the bug in the motivating example, so the undef is now a constant
0. This does mean converting between integer and floating point
constants, which may have different materialization.

Differential Revision: https://reviews.llvm.org/D135561

1 files changed, 6 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index f49d127..b9ffb8a 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -6122,6 +6122,7 @@ bool CodeGenPrepare::optimizePhiType(
   SmallVector<Instruction *, 4> Worklist;
   Worklist.push_back(cast<Instruction>(I));
   SmallPtrSet<PHINode *, 4> PhiNodes;
+  SmallPtrSet<ConstantData *, 4> Constants;
   PhiNodes.insert(I);
   Visited.insert(I);
   SmallPtrSet<Instruction *, 4> Defs;
@@ -6164,9 +6165,10 @@ bool CodeGenPrepare::optimizePhiType(
             AnyAnchored |= !isa<LoadInst>(OpBC->getOperand(0)) &&
                            !isa<ExtractElementInst>(OpBC->getOperand(0));
           }
-        } else if (!isa<UndefValue>(V)) {
+        } else if (auto *OpC = dyn_cast<ConstantData>(V))
+          Constants.insert(OpC);
+        else
           return false;
-        }
       }
     }
 
@@ -6208,7 +6210,8 @@ bool CodeGenPrepare::optimizePhiType(
   // Create all the new phi nodes of the new type, and bitcast any loads to the
   // correct type.
   ValueToValueMap ValMap;
-  ValMap[UndefValue::get(PhiTy)] = UndefValue::get(ConvertTy);
+  for (ConstantData *C : Constants)
+    ValMap[C] = ConstantExpr::getCast(Instruction::BitCast, C, ConvertTy);
   for (Instruction *D : Defs) {
     if (isa<BitCastInst>(D)) {
       ValMap[D] = D->getOperand(0);