[UBSan] make ubsantrap inaccessiblemem: write

[fmayer]

This is consistent with the normal trap. This will allow more
optimizations to work on it (e.g. it can be reordered more
freely).

This will also allow #155901 to avoid
hardcoding the ubsan trap.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-llvm-ir

Author: Florian Mayer (fmayer)

Changes

This is consistent with the normal trap. This will allow more
optimizations to work on it (e.g. it can be reordered more
freely).

---

Full diff: https://github.com/llvm/llvm-project/pull/156100.diff

1 Files Affected:

• (modified) llvm/include/llvm/IR/Intrinsics.td (+2-1)

diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index e0ee12391b31d..ca8bf6d7b912e 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -1834,7 +1834,8 @@ def int_trap : Intrinsic<[], [], [IntrNoReturn, IntrCold, IntrInaccessibleMemOnl
 def int_debugtrap : Intrinsic<[]>,
                     ClangBuiltin<"__builtin_debugtrap">;
 def int_ubsantrap : Intrinsic<[], [llvm_i8_ty],
-                              [IntrNoReturn, IntrCold, ImmArg<ArgIndex<0>>]>;
+                              [IntrNoReturn, IntrCold, ImmArg<ArgIndex<0>>,
+                               IntrInaccessibleMemOnly, IntrWriteMem]>;
 
 // Return true if ubsan check is allowed.
 def int_allow_ubsan_check : DefaultAttrsIntrinsic<[llvm_i1_ty], [llvm_i8_ty],

[nikic]

LGTM, assuming the intended usage model for these does not include introspection of memory at the time of trap.

[fmayer]

LGTM, assuming the intended usage model for these does not include introspection of memory at the time of trap.

Not more or less than a normal builtin_trap(). Someone might look at it in a debugger, or look at the crash stack trace.