1 files changed, 17 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index b318d0b2de9..5e0a3c37979 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4026,7 +4026,8 @@ Instruction *InstCombiner::foldICmpEquality(ICmpInst &I) {
   return nullptr;
 }
 
-static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp) {
+static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp,
+                                           InstCombiner::BuilderTy &Builder) {
   assert(isa<CastInst>(ICmp.getOperand(0)) && "Expected cast for operand 0");
   auto *CastOp0 = cast<CastInst>(ICmp.getOperand(0));
   Value *X;
@@ -4038,15 +4039,25 @@ static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp) {
   if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
     // If the signedness of the two casts doesn't agree (i.e. one is a sext
     // and the other is a zext), then we can't handle this.
+    // TODO: This is too strict. We can handle some predicates (equality?).
     if (CastOp0->getOpcode() != CastOp1->getOpcode())
       return nullptr;
 
     // Not an extension from the same type?
-    // TODO: Handle this by extending the narrower operand to the type of
-    //       the wider operand.
     Value *Y = CastOp1->getOperand(0);
-    if (X->getType() != Y->getType())
-      return nullptr;
+    Type *XTy = X->getType(), *YTy = Y->getType();
+    if (XTy != YTy) {
+      // One of the casts must have one use because we are creating a new cast.
+      if (!CastOp0->hasOneUse() && !CastOp1->hasOneUse())
+        return nullptr;
+      // Extend the narrower operand to the type of the wider operand.
+      if (XTy->getScalarSizeInBits() < YTy->getScalarSizeInBits())
+        X = Builder.CreateCast(CastOp0->getOpcode(), X, YTy);
+      else if (YTy->getScalarSizeInBits() < XTy->getScalarSizeInBits())
+        Y = Builder.CreateCast(CastOp0->getOpcode(), Y, XTy);
+      else
+        return nullptr;
+    }
 
     // (zext X) == (zext Y) --> X == Y
     // (sext X) == (sext Y) --> X == Y
@@ -4148,7 +4159,7 @@ Instruction *InstCombiner::foldICmpWithCastOp(ICmpInst &ICmp) {
       return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
   }
 
-  return foldICmpWithZextOrSext(ICmp);
+  return foldICmpWithZextOrSext(ICmp, Builder);
 }
 
 static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {