[IR] Do not set `none` for function uwtable (#93387)

This avoids the pitfall where we set the uwtable to none:
```
func.setUWTableKind(llvm::UWTableKind::None)
```
`Attribute::getAsString()` would see an unknown attribute and fail an
assertion. In this patch, we assert that we do not see a None uwtable
kind.

This also skips the check of `UWTableKind::Async`. It is dominated by
the check of `UWTableKind::Default`, which has the same enum value
(nfc).

1 files changed, 2 insertions, 7 deletions

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index c8d6bdd..7a3c9a9 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -526,13 +526,8 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
 
   if (hasAttribute(Attribute::UWTable)) {
     UWTableKind Kind = getUWTableKind();
-    if (Kind != UWTableKind::None) {
-      return Kind == UWTableKind::Default
-                 ? "uwtable"
-                 : ("uwtable(" +
-                    Twine(Kind == UWTableKind::Sync ? "sync" : "async") + ")")
-                       .str();
-    }
+    assert(Kind != UWTableKind::None && "uwtable attribute should not be none");
+    return Kind == UWTableKind::Default ? "uwtable" : "uwtable(sync)";
   }
 
   if (hasAttribute(Attribute::AllocKind)) {