[InstCombine] Fix incongruous GEP type addrspace

Currently running the @insertelem_after_gep function below through the InstCombine pass with opt produces invalid IR.

Input:
```
define void @insertelem_after_gep(<16 x i32>* %t0) {
   %t1 = bitcast <16 x i32>* %t0 to [16 x i32]*
   %t2 = addrspacecast [16 x i32]* %t1 to [16 x i32] addrspace(3)*
   %t3 = getelementptr inbounds [16 x i32], [16 x i32] addrspace(3)* %t2, i64 0, i64 0
   %t4 = insertelement <16 x i32 addrspace(3)*> undef, i32 addrspace(3)* %t3, i32 0
   call void @extern_vec_pointers_func(<16 x i32 addrspace(3)*> %t4)
   ret void
}
```

Output:

```
define void @insertelem_after_gep(<16 x i32>* %t0) {
  %t3 = getelementptr inbounds <16 x i32>, <16 x i32>* %t0, i64 0, i64 0
  %t4 = insertelement <16 x i32 addrspace(3)*> undef, i32 addrspace(3)* %t3, i32 0
  call void @my_extern_func(<16 x i32 addrspace(3)*> %t4)
  ret void
}
```

Which although causes no complaints when produced, isn't valid IR as the insertelement use of the %t3 GEP expects an address space.

```
opt: /tmp/bad.ll:52:73: error: '%t3' defined with type 'i32*' but expected 'i32 addrspace(3)*'
  %t4 = insertelement <16 x i32 addrspace(3)*> undef, i32 addrspace(3)* %t3, i32 0
```

I've fixed this by adding an addrspacecast after the GEP in the InstCombine pass, and including a check for this type mismatch to the verifier.

Reviewers: spatel, lebedev.ri
Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D52294

llvm-svn: 343956

1 files changed, 16 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 70fea859376..00ffe9e2dc2 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -2052,9 +2052,22 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
           areMatchingArrayAndVecTypes(GEPEltType, SrcEltType)) ||
          (GEPEltType->isVectorTy() && SrcEltType->isArrayTy() &&
           areMatchingArrayAndVecTypes(SrcEltType, GEPEltType)))) {
-      GEP.setOperand(0, SrcOp);
-      GEP.setSourceElementType(SrcEltType);
-      return &GEP;
+
+      // Create a new GEP here, as using `setOperand()` followed by
+      // `setSourceElementType()` won't actually update the type of the
+      // existing GEP Value. Causing issues if this Value is accessed when
+      // constructing an AddrSpaceCastInst
+      Value *NGEP =
+          GEP.isInBounds()
+              ? Builder.CreateInBoundsGEP(nullptr, SrcOp, {Ops[1], Ops[2]})
+              : Builder.CreateGEP(nullptr, SrcOp, {Ops[1], Ops[2]});
+      NGEP->takeName(&GEP);
+
+      // Preserve GEP address space to satisfy users
+      if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace())
+        return new AddrSpaceCastInst(NGEP, GEPType);
+
+      return replaceInstUsesWith(GEP, NGEP);
     }
 
     // See if we can simplify: