[PATCH] D150740: [clang] Add `__attribute__((nooutline))`

[Jessica Paquette via Phabricator via cfe-commits]

paquette created this revision.
paquette added reviewers: fhahn, aemerson, jroelofs, arphaman, ahatanak.
paquette added a project: clang.
Herald added a reviewer: aaron.ballman.
Herald added a subscriber: StephenFan.
Herald added a project: All.
paquette requested review of this revision.

Sometimes users want to toggle which functions should be outlined from. Users could be trying to:

1. Debug the compiler and disable outlining in some contexts
2. Control where outlining actually happens in their program

This adds a frontend attribute that will allow users to toggle this behaviour on specific functions.


https://reviews.llvm.org/D150740

Files:
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CGCall.cpp
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nooutline.c


Index: clang/test/CodeGen/attr-nooutline.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-nooutline.c
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 %s -S -emit-llvm -o - | FileCheck %s
+
+// CHECK: define i32 @has_attr_2() [[HAS_ATTR_2:#[0-9]+]]
+// CHECK: declare i32 @has_attr_1() [[HAS_ATTR_1:#[0-9]+]]
+
+__attribute__((nooutline)) int has_attr_1(void);
+__attribute__((nooutline)) int has_attr_2(void) { return has_attr_1(); }
+
+// CHECK: attributes [[HAS_ATTR_2]] = { {{.*}}"nooutline"{{.*}} }
+// CHECK: attributes [[HAS_ATTR_1]] = { {{.*}}"nooutline"{{.*}} }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -2133,6 +2133,8 @@
     if (D->hasAttr<MinSizeAttr>())
       B.addAttribute(llvm::Attribute::MinSize);
   }
+  if (D->hasAttr<NoOutlineAttr>())
+    B.addAttribute("nooutline");
 
   F->addFnAttrs(B);
 
Index: clang/lib/CodeGen/CGCall.cpp
===================================================================
--- clang/lib/CodeGen/CGCall.cpp
+++ clang/lib/CodeGen/CGCall.cpp
@@ -2344,6 +2344,8 @@
       FuncAttrs.addAttribute(llvm::Attribute::NoCfCheck);
     if (TargetDecl->hasAttr<LeafAttr>())
       FuncAttrs.addAttribute(llvm::Attribute::NoCallback);
+    if (TargetDecl->hasAttr<NoOutlineAttr>())
+      FuncAttrs.addAttribute("nooutline");
 
     HasOptnone = TargetDecl->hasAttr<OptimizeNoneAttr>();
     if (auto *AllocSize = TargetDecl->getAttr<AllocSizeAttr>()) {
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -580,6 +580,26 @@
   }];
 }
 
+def NoOutlineDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+
+Suppresses outlining from a function. Functions with this attribute will not
+be considered for outlining.
+
+.. code-block:: c
+
+  __attribute__((nooutline))
+  int example(void) {
+    int r;
+    foo();
+    bar();
+    return r;
+  }
+
+  }];
+}
+
 def MustTailDocs : Documentation {
   let Category = DocCatStmt;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1469,6 +1469,13 @@
   let SimpleHandler = 1;
 }
 
+def NoOutline : InheritableAttr {
+  let Spellings = [Clang<"nooutline">];
+  let Subjects = SubjectList<[Function, ObjCMethod]>;
+  let Documentation = [NoOutlineDocs];
+  let SimpleHandler = 1;
+}
+
 def MustTail : StmtAttr {
   let Spellings = [Clang<"musttail">];
   let Documentation = [MustTailDocs];


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