[llvm] [InstCombine] Handle ptrtoaddr in gep of pointer sub fold (PR #164818)

[Alexander Richardson via llvm-commits]

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@@ -171,3 +175,60 @@ define i128 @sub_zext_ptrtoint_ptrtoaddr_addrsize(ptr addrspace(1) %p, i32 %offs
   %sub = sub i128 %p2.addr.ext, %p.int.ext
   ret i128 %sub
 }
+
+define ptr @gep_sub_ptrtoaddr_different_obj(ptr %p, ptr %p2, ptr %p3) {
+; CHECK-LABEL: define ptr @gep_sub_ptrtoaddr_different_obj(
+; CHECK-SAME: ptr [[P:%.*]], ptr [[P2:%.*]], ptr [[P3:%.*]]) {
+; CHECK-NEXT:    [[P_ADDR:%.*]] = ptrtoaddr ptr [[P]] to i64
+; CHECK-NEXT:    [[P2_ADDR:%.*]] = ptrtoaddr ptr [[P2]] to i64
+; CHECK-NEXT:    [[SUB:%.*]] = sub i64 [[P2_ADDR]], [[P_ADDR]]
+; CHECK-NEXT:    [[GEP:%.*]] = getelementptr i8, ptr [[P]], i64 [[SUB]]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[P2]], [[P3]]
+; CHECK-NEXT:    call void @use.i1(i1 [[CMP]])
+; CHECK-NEXT:    [[INT:%.*]] = ptrtoint ptr [[P2]] to i64
+; CHECK-NEXT:    call void @use.i64(i64 [[INT]])
+; CHECK-NEXT:    [[ADDR:%.*]] = ptrtoaddr ptr [[P2]] to i64
+; CHECK-NEXT:    call void @use.i64(i64 [[ADDR]])
+; CHECK-NEXT:    ret ptr [[GEP]]
+;
+  %p.addr = ptrtoaddr ptr %p to i64
+  %p2.addr = ptrtoaddr ptr %p2 to i64
+  %sub = sub i64 %p2.addr, %p.addr
+  %gep = getelementptr i8, ptr %p, i64 %sub
+  %cmp = icmp eq ptr %gep, %p3
+  call void @use.i1(i1 %cmp)
+  %int = ptrtoint ptr %gep to i64
+  call void @use.i64(i64 %int)
+  %addr = ptrtoaddr ptr %gep to i64
+  call void @use.i64(i64 %addr)
+  ret ptr %gep
+}
+
+define ptr addrspace(1) @gep_sub_ptrtoaddr_different_obj_addrsize(ptr addrspace(1) %p, ptr addrspace(1) %p2, ptr addrspace(1) %p3) {
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arichardson wrote:

Maybe add a comment above this function that ptrtoint should not be folded just to make it easier to understand what is being tested? I initially had to look at this a few times since only the file check variable name differs. 

https://github.com/llvm/llvm-project/pull/164818