gep.diff

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 4fc6b4de976b..ca62e6504856 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2057,10 +2057,19 @@ Instruction *InstCombinerImpl::visitGEPOfGEP(GetElementPtrInst &GEP,
       return nullptr;
 
     // Convert the total offset back into indices.
+    APInt OrigOffset = Offset;
     SmallVector<APInt> ConstIndices =
         DL.getGEPIndicesForOffset(BaseType, Offset);
-    if (!Offset.isZero() || (!IsFirstType && !ConstIndices[0].isZero()))
+    if (!Offset.isZero() || (!IsFirstType && !ConstIndices[0].isZero())) {
+      // When combining two constant GEPs, fall back to i8 element type.
+      if (Src->hasAllConstantIndices())
+        return replaceInstUsesWith(
+            GEP, Builder.CreateGEP(
+                     Builder.getInt8Ty(), Src->getPointerOperand(),
+                     Builder.getInt(OrigOffset), "",
+                     isMergedGEPInBounds(*Src, *cast<GEPOperator>(&GEP))));
       return nullptr;
+    }
 
     SmallVector<Value *> Indices;
     append_range(Indices, drop_end(Src->indices(),