llvm: migrate to new parameter-bearing uwtable attr

In https://reviews.llvm.org/D114543 the uwtable attribute gained a flag
so that we can ask for sync uwtables instead of async, as the former are
much cheaper. The default is async, so that's what I've done here, but I
left a TODO that we might be able to do better.

While in here I went ahead and dropped support for removing uwtable
attributes in rustc: we never did it, so I didn't write the extra C++
bridge code to make it work. Maybe I should have done the same thing
with the `sync|async` parameter but we'll see.

1 files changed, 11 insertions, 0 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index fb9c5e6a527..23333199506 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -334,6 +334,17 @@ extern "C" void LLVMRustAddStructRetAttr(LLVMValueRef Fn, unsigned Index,
   AddAttribute(F, Index, Attr);
 }
 
+extern "C" void LLVMRustEmitUWTableAttr(LLVMValueRef Fn, bool Async) {
+  Function *F = unwrap<Function>(Fn);
+#if LLVM_VERSION_LT(15, 0)
+  Attribute Attr = Attribute::get(F->getContext(), Attribute::UWTable);
+#else
+  Attribute Attr = Attribute::getWithUWTableKind(
+      F->getContext(), Async ? UWTableKind::Async : UWTableKind::Sync);
+#endif
+  AddAttribute(F, AttributeList::AttrIndex::FunctionIndex, Attr);
+}
+
 extern "C" void LLVMRustAddFunctionAttrStringValue(LLVMValueRef Fn,
                                                    unsigned Index,
                                                    const char *Name,