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

[Joshua Cao via llvm-commits]

https://github.com/caojoshua updated https://github.com/llvm/llvm-project/pull/93387

>From 78be05f968797490558ece3f70669b494ea5fb0b Mon Sep 17 00:00:00 2001
From: Joshua Cao <cao.joshua at yahoo.com>
Date: Sat, 25 May 2024 16:11:55 -0700
Subject: [PATCH 1/2] [IR] Do not set `none` for function uwtable

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).
---
 llvm/include/llvm/IR/Function.h      |  3 ++-
 llvm/lib/CodeGen/MachineOutliner.cpp |  3 +--
 llvm/lib/IR/Attributes.cpp           | 10 +++-------
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/llvm/include/llvm/IR/Function.h b/llvm/include/llvm/IR/Function.h
index cb514cde95b51..be745a0083cb7 100644
--- a/llvm/include/llvm/IR/Function.h
+++ b/llvm/include/llvm/IR/Function.h
@@ -654,7 +654,8 @@ class LLVM_EXTERNAL_VISIBILITY Function : public GlobalObject,
     return getUWTableKind() != UWTableKind::None;
   }
   void setUWTableKind(UWTableKind K) {
-    addFnAttr(Attribute::getWithUWTableKind(getContext(), K));
+    if (K != UWTableKind::None)
+      addFnAttr(Attribute::getWithUWTableKind(getContext(), K));
   }
   /// True if this function needs an unwind table.
   bool needsUnwindTableEntry() const {
diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp
index dc2f5ef15206e..f174dd857def0 100644
--- a/llvm/lib/CodeGen/MachineOutliner.cpp
+++ b/llvm/lib/CodeGen/MachineOutliner.cpp
@@ -717,8 +717,7 @@ MachineFunction *MachineOutliner::createOutlinedFunction(
       [](UWTableKind K, const outliner::Candidate &C) {
         return std::max(K, C.getMF()->getFunction().getUWTableKind());
       });
-  if (UW != UWTableKind::None)
-    F->setUWTableKind(UW);
+  F->setUWTableKind(UW);
 
   BasicBlock *EntryBB = BasicBlock::Create(C, "entry", F);
   IRBuilder<> Builder(EntryBB);
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index c8d6bdd423878..cc3a2ceb6de84 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -526,13 +526,9 @@ 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)) {

>From 6f32102b92aa00ab04f3fa1d399da61faee47088 Mon Sep 17 00:00:00 2001
From: Joshua Cao <cao.joshua at yahoo.com>
Date: Sat, 25 May 2024 16:45:12 -0700
Subject: [PATCH 2/2] Fix formatting

---
 llvm/lib/IR/Attributes.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
index cc3a2ceb6de84..7a3c9a99ee4d8 100644
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -526,8 +526,7 @@ std::string Attribute::getAsString(bool InAttrGrp) const {
 
   if (hasAttribute(Attribute::UWTable)) {
     UWTableKind Kind = getUWTableKind();
-    assert(Kind != UWTableKind::None &&
-           "uwtable attribute should not be none");
+    assert(Kind != UWTableKind::None && "uwtable attribute should not be none");
     return Kind == UWTableKind::Default ? "uwtable" : "uwtable(sync)";
   }