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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-amdgpu

Author: Pierre van Houtryve (Pierre-vh)

<details>
<summary>Changes</summary>

All other opcodes in the list are constrained to have the same type on both operands, but not G_PTR_ADD.

Fixes  #<!-- -->81464

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


2 Files Affected:

- (modified) llvm/lib/CodeGen/GlobalISel/Utils.cpp (+8-1) 
- (added) llvm/test/CodeGen/AMDGPU/GlobalISel/combine-extract-vector-load.mir (+20) 


``````````diff
diff --git a/llvm/lib/CodeGen/GlobalISel/Utils.cpp b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
index 26fd12f9e51c43..d693316dc6e9d7 100644
--- a/llvm/lib/CodeGen/GlobalISel/Utils.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Utils.cpp
@@ -660,8 +660,15 @@ std::optional<APInt> llvm::ConstantFoldBinOp(unsigned Opcode,
   default:
     break;
   case TargetOpcode::G_ADD:
-  case TargetOpcode::G_PTR_ADD:
     return C1 + C2;
+  case TargetOpcode::G_PTR_ADD: {
+    // Types can be of different width here.
+    if (C1.getBitWidth() < C2.getBitWidth())
+      return C1.zext(C1.getBitWidth()) + C2;
+    if (C1.getBitWidth() > C2.getBitWidth())
+      return C2.zext(C1.getBitWidth()) + C1;
+    return C1 + C2;
+  }
   case TargetOpcode::G_AND:
     return C1 & C2;
   case TargetOpcode::G_ASHR:
diff --git a/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-extract-vector-load.mir b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-extract-vector-load.mir
new file mode 100644
index 00000000000000..13be65612fa855
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/GlobalISel/combine-extract-vector-load.mir
@@ -0,0 +1,20 @@
+# 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
+
+---
+name:            test_ptradd_crash
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    ; CHECK-LABEL: name: test_ptradd_crash
+    ; CHECK: [[C:%[0-9]+]]:_(p1) = G_CONSTANT i64 0
+    ; 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 0
+    %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
+...

``````````

</details>


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