[llvm] [GlobalISel] Constant-fold G_PTR_ADD with different type sizes (PR #81473)

[Pierre van Houtryve via llvm-commits]

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@@ -0,0 +1,40 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn -run-pass=amdgpu-prelegalizer-combiner -verify-machineinstrs %s -o - | FileCheck %s
+
+# Tries to emit a foldable G_PTR_ADD with (p1, s32) operands.
+---
+name:            test_ptradd_crash__offset_smaller
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    ; CHECK-LABEL: name: test_ptradd_crash__offset_smaller
+    ; CHECK: [[C:%[0-9]+]]:_(p1) = G_CONSTANT i64 12
+    ; CHECK-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[C]](p1) :: (load (s32), addrspace 1)
+    ; CHECK-NEXT: $sgpr0 = COPY [[LOAD]](s32)
+    ; CHECK-NEXT: SI_RETURN_TO_EPILOG implicit $sgpr0
+    %1:_(p1) = G_CONSTANT i64 0
+    %3:_(s32) = G_CONSTANT i32 3
+    %0:_(<4 x s32>) = G_LOAD %1 :: (load (<4 x s32>) from `ptr addrspace(1) null`, addrspace 1)
+    %2:_(s32) = G_EXTRACT_VECTOR_ELT %0, %3
+    $sgpr0 = COPY %2
+    SI_RETURN_TO_EPILOG implicit $sgpr0
+...
+
+# Tries to emit a foldable G_PTR_ADD with (p1, s128) operands.
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Pierre-vh wrote:

It should, `MachineVerifier` doesn't check for it + `MachineIRBuilder` doesn't complain

I can make a follow-up patch to enforce `RHS <= LHS` if you want

https://github.com/llvm/llvm-project/pull/81473