[llvm] [IR] Fix incorrect writeonly on llvm.allow.ubsan/runtime.check (PR #145492)

[Nikita Popov via llvm-commits]

https://github.com/nikic created https://github.com/llvm/llvm-project/pull/145492

These intrinsics introduced in #84850 are currently marked as `memory(inaccessiblemem: write)`. This is not correct for the intended purpose of allowing per-block decisions, as such calls may get DCEd across control-flow boundaries (which will start actually happening with #145474).

Use `memory(inaccessiblemem: readwrite)` instead, just like all the other control-flow sensitive intrinsics.

>From 88e3d4013ed593796e2c604a34d2e50f78b46189 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov at redhat.com>
Date: Tue, 24 Jun 2025 11:38:35 +0200
Subject: [PATCH] [IR] Fix incorrect writeonly on
 llvm.allow.ubsan/runtime.check

These intrinsics introduced in #84850 are currently marked as
`memory(inaccessiblemem: write)`. This is not correct for the
intended purpose of allowing per-block decisions, as such calls
may get DCEd across control-flow boundaries (which will start
actually happening with #145474).

Use `memory(inaccessiblemem: readwrite)` instead, just like all
the other control-flow sensitive intrinsics.
---
 llvm/include/llvm/IR/Intrinsics.td                   | 4 ++--
 llvm/test/Instrumentation/BoundsChecking/runtimes.ll | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 7add4a27ce9e9..bd6f94ac1286c 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -1842,11 +1842,11 @@ def int_ubsantrap : Intrinsic<[], [llvm_i8_ty],
 
 // Return true if ubsan check is allowed.
 def int_allow_ubsan_check : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_i8_ty],
-    [IntrInaccessibleMemOnly, IntrWriteMem, ImmArg<ArgIndex<0>>, NoUndef<RetIndex>]>;
+    [IntrInaccessibleMemOnly, ImmArg<ArgIndex<0>>, NoUndef<RetIndex>]>;
 
 // Return true if runtime check is allowed.
 def int_allow_runtime_check : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_metadata_ty],
-    [IntrInaccessibleMemOnly, IntrWriteMem, NoUndef<RetIndex>]>,
+    [IntrInaccessibleMemOnly, NoUndef<RetIndex>]>,
     ClangBuiltin<"__builtin_allow_runtime_check">;
 
 // Support for dynamic deoptimization (or de-specialization)
diff --git a/llvm/test/Instrumentation/BoundsChecking/runtimes.ll b/llvm/test/Instrumentation/BoundsChecking/runtimes.ll
index 6c1acf6d13775..2006a6db2ef40 100644
--- a/llvm/test/Instrumentation/BoundsChecking/runtimes.ll
+++ b/llvm/test/Instrumentation/BoundsChecking/runtimes.ll
@@ -205,7 +205,7 @@ define void @f1(i64 %x) nounwind {
 ; TR-GUARD: attributes #[[ATTR3]] = { nomerge noreturn nounwind }
 ;.
 ; RT-GUARD: attributes #[[ATTR0]] = { nounwind }
-; RT-GUARD: attributes #[[ATTR1:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }
+; RT-GUARD: attributes #[[ATTR1:[0-9]+]] = { nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: readwrite) }
 ; RT-GUARD: attributes #[[ATTR2]] = { nomerge nounwind }
 ;.
 ; TR: [[META0]] = !{}