[rtsan][llvm][NFC] Rename sanitize_realtime_unsafe attr to sanitize_realtime_blocking (#113155)

# What

This PR renames the newly-introduced llvm attribute
`sanitize_realtime_unsafe` to `sanitize_realtime_blocking`. Likewise,
sibling variables such as `SanitizeRealtimeUnsafe` are renamed to
`SanitizeRealtimeBlocking` respectively. There are no other functional
changes.


# Why?

- There are a number of problems that can cause a function to be
real-time "unsafe",
- we wish to communicate what problems rtsan detects and *why* they're
unsafe, and
- a generic "unsafe" attribute is, in our opinion, too broad a net -
which may lead to future implementations that need extra contextual
information passed through them in order to communicate meaningful
reasons to users.
- We want to avoid this situation and make the runtime library boundary
API/ABI as simple as possible, and
- we believe that restricting the scope of attributes to names like
`sanitize_realtime_blocking` is an effective means of doing so.

We also feel that the symmetry between `[[clang::blocking]]` and
`sanitize_realtime_blocking` is easier to follow as a developer.

# Concerns

- I'm aware that the LLVM attribute `sanitize_realtime_unsafe` has been
part of the tree for a few weeks now (introduced here:
https://github.com/llvm/llvm-project/pull/106754). Given that it hasn't
been released in version 20 yet, am I correct in considering this to not
be a breaking change?

1 files changed, 1 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 573ced0..6ead457 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -852,7 +852,7 @@ void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
         if (Fe.Effect.kind() == FunctionEffect::Kind::NonBlocking)
           Fn->addFnAttr(llvm::Attribute::SanitizeRealtime);
         else if (Fe.Effect.kind() == FunctionEffect::Kind::Blocking)
-          Fn->addFnAttr(llvm::Attribute::SanitizeRealtimeUnsafe);
+          Fn->addFnAttr(llvm::Attribute::SanitizeRealtimeBlocking);
       }
 
   // Apply fuzzing attribute to the function.