[compiler-rt] [NFC] [HWASan] clarify FIXME comment (PR #87689)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Florian Mayer (fmayer)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/87689.diff


1 Files Affected:

- (modified) compiler-rt/lib/hwasan/hwasan_thread_list.h (+3) 


``````````diff
diff --git a/compiler-rt/lib/hwasan/hwasan_thread_list.h b/compiler-rt/lib/hwasan/hwasan_thread_list.h
index f36d27864fc207..5eeb771cdf8203 100644
--- a/compiler-rt/lib/hwasan/hwasan_thread_list.h
+++ b/compiler-rt/lib/hwasan/hwasan_thread_list.h
@@ -55,6 +55,9 @@ static uptr RingBufferSize() {
   uptr desired_bytes = flags()->stack_history_size * sizeof(uptr);
   // FIXME: increase the limit to 8 once this bug is fixed:
   // https://bugs.llvm.org/show_bug.cgi?id=39030
+  // Note that we *cannot* do that on Android, as the runtime will indefinitely
+  // have to support code that is compield with ashr, which only works with
+  // shifts up to 6.
   for (int shift = 0; shift < 7; ++shift) {
     uptr size = 4096 * (1ULL << shift);
     if (size >= desired_bytes)

``````````

</details>


https://github.com/llvm/llvm-project/pull/87689