[llvm-branch-commits] [clang] [clang] Add clang::nooutline Attribute (PR #163666)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Sam Elliott (lenary)

<details>
<summary>Changes</summary>

This change:
- Adds a `[[clang::nooutline]]` function attribute for C and C++. There
  is no equivalent GNU syntax for this attribute, so no `__attribute__`
  syntax.
- Uses the presence of `[[clang::nooutline]]` to add the `nooutline`
  attribute to IR function definitions.
- Adds test for the above.

The `nooutline` attribute disables both the Machine Outliner (enabled at
Oz for some targets), and the IR Outliner (disabled by default).

---
Full diff: https://github.com/llvm/llvm-project/pull/163666.diff


6 Files Affected:

- (modified) clang/include/clang/Basic/Attr.td (+7) 
- (modified) clang/lib/CodeGen/CodeGenModule.cpp (+3) 
- (added) clang/test/CodeGen/attr-nooutline.c (+16) 
- (modified) clang/test/Misc/pragma-attribute-supported-attributes-list.test (+1) 
- (added) clang/test/Sema/attr-nooutline.c (+7) 
- (added) clang/test/Sema/attr-nooutline.cpp (+7) 


``````````diff
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 22e60aa9fe312..b8a61ba4cbac9 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -2355,6 +2355,13 @@ def NoInline : DeclOrStmtAttr {
   let SimpleHandler = 1;
 }
 
+def NoOutline : DeclOrStmtAttr {
+  let Spellings = [CXX11<"clang", "nooutline">, C23<"clang", "nooutline">];
+  let Subjects = SubjectList<[Function], ErrorDiag>;
+  let Documentation = [Undocumented];
+  let SimpleHandler = 1;
+}
+
 def NoMips16 : InheritableAttr, TargetSpecificAttr<TargetMips32> {
   let Spellings = [GCC<"nomips16">];
   let Subjects = SubjectList<[Function], ErrorDiag>;
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 8d019d4b2da25..ab267236ed579 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2820,6 +2820,9 @@ void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
       B.addAttribute(llvm::Attribute::MinSize);
   }
 
+  if (D->hasAttr<NoOutlineAttr>())
+    B.addAttribute(llvm::Attribute::NoOutline);
+
   F->addFnAttrs(B);
 
   unsigned alignment = D->getMaxAlignment() / Context.getCharWidth();
diff --git a/clang/test/CodeGen/attr-nooutline.c b/clang/test/CodeGen/attr-nooutline.c
new file mode 100644
index 0000000000000..b9f175da24cb5
--- /dev/null
+++ b/clang/test/CodeGen/attr-nooutline.c
@@ -0,0 +1,16 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-attributes --version 6
+// RUN: %clang_cc1 -emit-llvm %s -triple x86_64-unknown-linux-gnu -disable-O0-optnone -o - | FileCheck %s
+
+
+// CHECK: Function Attrs: noinline nooutline nounwind
+// CHECK-LABEL: define dso_local i32 @t1(
+// CHECK-SAME: i32 noundef [[X:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[X_ADDR:%.*]] = alloca i32, align 4
+// CHECK-NEXT:    store i32 [[X]], ptr [[X_ADDR]], align 4
+// CHECK-NEXT:    [[TMP0:%.*]] = load i32, ptr [[X_ADDR]], align 4
+// CHECK-NEXT:    ret i32 [[TMP0]]
+//
+[[clang::nooutline]] int t1(int x) {
+  return x;
+}
diff --git a/clang/test/Misc/pragma-attribute-supported-attributes-list.test b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
index 73d4cb1769ed5..7ef758dbea9eb 100644
--- a/clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ b/clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -123,6 +123,7 @@
 // CHECK-NEXT: NoMerge (SubjectMatchRule_function, SubjectMatchRule_variable)
 // CHECK-NEXT: NoMicroMips (SubjectMatchRule_function)
 // CHECK-NEXT: NoMips16 (SubjectMatchRule_function)
+// CHECK-NEXT: NoOutline (SubjectMatchRule_function)
 // CHECK-NEXT: NoProfileFunction (SubjectMatchRule_function)
 // CHECK-NEXT: NoRandomizeLayout (SubjectMatchRule_record)
 // CHECK-NEXT: NoSanitize (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_variable_is_global)
diff --git a/clang/test/Sema/attr-nooutline.c b/clang/test/Sema/attr-nooutline.c
new file mode 100644
index 0000000000000..83848c22d1003
--- /dev/null
+++ b/clang/test/Sema/attr-nooutline.c
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only
+
+[[clang::nooutline]] int a; // expected-error {{'clang::nooutline' attribute only applies to functions}}
+
+[[clang::nooutline]] void t1(void);
+
+[[clang::nooutline(2)]] void t2(void); // expected-error {{'clang::nooutline' attribute takes no arguments}}
diff --git a/clang/test/Sema/attr-nooutline.cpp b/clang/test/Sema/attr-nooutline.cpp
new file mode 100644
index 0000000000000..b6c9b3995081a
--- /dev/null
+++ b/clang/test/Sema/attr-nooutline.cpp
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 -verify -fsyntax-only %s -Wno-c++17-extensions
+
+[[clang::nooutline]] int a; // expected-error {{'clang::nooutline' attribute only applies to functions}}
+
+[[clang::nooutline]] void t1(void);
+
+[[clang::nooutline(2)]] void t2(void); // expected-error {{'clang::nooutline' attribute takes no arguments}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/163666