[clang] [llvm] IR: Make llvm.fake.use a DefaultAttrsIntrinsic (PR #131743)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm updated https://github.com/llvm/llvm-project/pull/131743

>From 6b3a82b7191ab6ef0f30077adc980f5c5bfbd63f Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Tue, 18 Mar 2025 13:06:59 +0700
Subject: [PATCH] IR: Make llvm.fake.use a DefaultAttrsIntrinsic

This shouldn't be special and is just an ordinary sideeffect.
---
 clang/test/CodeGen/fake-use-determinism.c              | 6 +++---
 llvm/include/llvm/IR/Intrinsics.td                     | 3 ++-
 llvm/test/CodeGen/AMDGPU/lower-kernargs.ll             | 4 ++--
 llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp | 2 ++
 4 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/clang/test/CodeGen/fake-use-determinism.c b/clang/test/CodeGen/fake-use-determinism.c
index 039d8de692431..29f72aa0cc512 100644
--- a/clang/test/CodeGen/fake-use-determinism.c
+++ b/clang/test/CodeGen/fake-use-determinism.c
@@ -5,11 +5,11 @@
 // but that it remains the same between different test runs.
 
 // CHECK:      [[K_FAKE_USE:%[a-zA-Z0-9\.]+]] = load i32, ptr %k.addr
-// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[K_FAKE_USE]]) #2
+// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[K_FAKE_USE]])
 // CHECK-NEXT: [[J_FAKE_USE:%[a-zA-Z0-9\.]+]] = load i32, ptr %j.addr
-// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[J_FAKE_USE]]) #2
+// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[J_FAKE_USE]])
 // CHECK-NEXT: [[I_FAKE_USE:%[a-zA-Z0-9\.]+]] = load i32, ptr %i.addr
-// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[I_FAKE_USE]]) #2
+// CHECK-NEXT: call void (...) @llvm.fake.use(i32 [[I_FAKE_USE]])
 
 void bar();
 void foo(int i, int j, int k)
diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 62239ca705b9e..a1e2e120013f6 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -1881,7 +1881,8 @@ def int_is_constant : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_any_ty],
                                 "llvm.is.constant">;
 
 // Introduce a use of the argument without generating any code.
-def int_fake_use : Intrinsic<[], [llvm_vararg_ty]>;
+def int_fake_use : DefaultAttrsIntrinsic<[], [llvm_vararg_ty],
+  [IntrHasSideEffects, IntrNoMem, IntrWillReturn]>;
 
 // Intrinsic to mask out bits of a pointer.
 // First argument must be pointer or vector of pointer. This is checked by the
diff --git a/llvm/test/CodeGen/AMDGPU/lower-kernargs.ll b/llvm/test/CodeGen/AMDGPU/lower-kernargs.ll
index f6ee2090221c5..119beb958f1bd 100644
--- a/llvm/test/CodeGen/AMDGPU/lower-kernargs.ll
+++ b/llvm/test/CodeGen/AMDGPU/lower-kernargs.ll
@@ -1837,13 +1837,13 @@ attributes #2 = { nounwind "target-cpu"="tahiti" }
 !llvm.module.flags = !{!0}
 !0 = !{i32 1, !"amdhsa_code_object_version", i32 500}
 ;.
-; HSA: attributes #[[ATTR0:[0-9]+]] = { nounwind }
+; HSA: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }
 ; HSA: attributes #[[ATTR1:[0-9]+]] = { nounwind "target-cpu"="kaveri" }
 ; HSA: attributes #[[ATTR2:[0-9]+]] = { nounwind "amdgpu-implicitarg-num-bytes"="40" "target-cpu"="kaveri" }
 ; HSA: attributes #[[ATTR3:[0-9]+]] = { nounwind "target-cpu"="tahiti" }
 ; HSA: attributes #[[ATTR4:[0-9]+]] = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }
 ;.
-; MESA: attributes #[[ATTR0:[0-9]+]] = { nounwind }
+; MESA: attributes #[[ATTR0:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }
 ; MESA: attributes #[[ATTR1:[0-9]+]] = { nounwind "target-cpu"="kaveri" }
 ; MESA: attributes #[[ATTR2:[0-9]+]] = { nounwind "amdgpu-implicitarg-num-bytes"="40" "target-cpu"="kaveri" }
 ; MESA: attributes #[[ATTR3:[0-9]+]] = { nounwind "target-cpu"="tahiti" }
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp b/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
index a04f35498d7aa..406710ed96fae 100644
--- a/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceOperandsToArgs.cpp
@@ -113,6 +113,8 @@ static void substituteOperandWithArgument(Function *OldF,
   for (Use *Op : OpsToReplace)
     UniqueValues.insert(Op->get());
 
+  // TODO: Preserve range metadata with ranges
+
   // Determine the new function's signature.
   SmallVector<Type *> NewArgTypes;
   llvm::append_range(NewArgTypes, OldF->getFunctionType()->params());