[AMDGPU][LowerBufferFatPointers] Erase dead ptr(7) intrinsics

[krzysz00]

Fix a crash that would arise when intrinsics like llvm.masked.load.T.p7 were left in the module when AMDGPULowerBufferFatPointers was applied and so a captures(none) annotation would be applied to a non-pointer value, triggering a verifier failure.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Krzysztof Drewniak (krzysz00)

Changes

Fix a crash that would arise when intrinsics like llvm.masked.load.T.p7 were left in the module when AMDGPULowerBufferFatPointers was applied and so a captures(none) annotation would be applied to a non-pointer value, triggering a verifier failure.

---

Full diff: https://github.com/llvm/llvm-project/pull/160798.diff

2 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp (+3-1)
• (added) llvm/test/CodeGen/AMDGPU/lower-buffer-fat-pointers-dead-intrinsics.ll (+11)

diff --git a/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp b/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
index d9bfeae52e213..eac3329d00f9b 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPULowerBufferFatPointers.cpp
@@ -2562,7 +2562,9 @@ bool AMDGPULowerBufferFatPointers::run(Module &M, const TargetMachine &TM) {
   for (Function *F : NeedsPostProcess)
     Splitter.processFunction(*F);
   for (Function *F : Intrinsics) {
-    if (isRemovablePointerIntrinsic(F->getIntrinsicID())) {
+    // use_empty() can also occor with cases like malked load, which will
+    // have been rewritten out of the module by now but not erased.
+    if (F->use_empty() || isRemovablePointerIntrinsic(F->getIntrinsicID())) {
       F->eraseFromParent();
     } else {
       std::optional<Function *> NewF = Intrinsic::remangleIntrinsicFunction(F);
diff --git a/llvm/test/CodeGen/AMDGPU/lower-buffer-fat-pointers-dead-intrinsics.ll b/llvm/test/CodeGen/AMDGPU/lower-buffer-fat-pointers-dead-intrinsics.ll
new file mode 100644
index 0000000000000..a156ecdc4b53b
--- /dev/null
+++ b/llvm/test/CodeGen/AMDGPU/lower-buffer-fat-pointers-dead-intrinsics.ll
@@ -0,0 +1,11 @@
+; RUN: opt -S -mcpu=gfx900 -amdgpu-lower-buffer-fat-pointers < %s | FileCheck %s
+; RUN: opt -S -mcpu=gfx900 -passes=amdgpu-lower-buffer-fat-pointers < %s | FileCheck %s
+
+target triple = "amdgcn-amd-amdhsa"
+
+; CHECK: @arbitrary
+declare amdgpu_kernel void @arbitrary(ptr addrspace(1))
+
+; COM: This used to cause verifier errors when "lowered"
+declare <4 x i8> @llvm.masked.load.v4i8.p7(ptr addrspace(7) captures(none), i32 immarg, <4 x i1>, <4 x i8>)
+; CHECK-NOT: llvm.masked.load