[InstCombine] Fix incongruous GEP type addrspace

[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