https://github.com/yamt created https://github.com/llvm/llvm-project/pull/92499
It simply applies the LLVM attribute with the same name to the function.
Sometimes, a programmer knows that function pointer uniqueness doesn't really
matter for some of their functions. In that case, this attribute opens a
possibility of certain optimizations like mergefunc with aliases. It's
especially useful for code generators.
>From 1c1bedf655de10d2e4f0122975db1950f2203a96 Mon Sep 17 00:00:00 2001
From: YAMAMOTO Takashi <yamam...@midokura.com>
Date: Fri, 17 May 2024 14:47:06 +0900
Subject: [PATCH] clang: add unnamed_addr function attribute
It simply applies the LLVM attribute with the same name to the function.
Sometimes, a programmer knows that function pointer uniqueness doesn't
really matter for some of their functions. In that case, this attribute
opens a possibility of certain optimizations like mergefunc with aliases.
It's especially useful for code generators.
---
clang/include/clang/Basic/Attr.td | 7 +++++++
clang/lib/CodeGen/CodeGenModule.cpp | 4 ++++
2 files changed, 11 insertions(+)
diff --git a/clang/include/clang/Basic/Attr.td
b/clang/include/clang/Basic/Attr.td
index 52552ba488560..3ee7d43d339f1 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1944,6 +1944,13 @@ def ReturnsTwice : InheritableAttr {
let SimpleHandler = 1;
}
+def UnnamedAddr : InheritableAttr {
+ let Spellings = [Clang<"unnamed_addr">];
+ let Subjects = SubjectList<[Function]>;
+ let Documentation = [Undocumented];
+ let SimpleHandler = 1;
+}
+
def DisableTailCalls : InheritableAttr {
let Spellings = [Clang<"disable_tail_calls">];
let Subjects = SubjectList<[Function, ObjCMethod]>;
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp
b/clang/lib/CodeGen/CodeGenModule.cpp
index 489c08a4d4819..ac9f082a1049b 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2506,6 +2506,10 @@ void
CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
B.addAttribute(llvm::Attribute::MinSize);
}
+ if (D->hasAttr<UnnamedAddrAttr>()) {
+ F->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+ }
+
F->addFnAttrs(B);
unsigned alignment = D->getMaxAlignment() / Context.getCharWidth();
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