[PATCH] D132592: [Clang] Implement function attribute nouwtable

[Yuanfang Chen via Phabricator via cfe-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG70248bfdea6c: [Clang] Implement function attribute nouwtable (authored by ychen).

Changed prior to commit:
  https://reviews.llvm.org/D132592?vs=456403&id=456433#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D132592/new/

https://reviews.llvm.org/D132592

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/Attr.td
  clang/include/clang/Basic/AttrDocs.td
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/test/CodeGen/attr-nouwtable.c
  clang/test/Misc/pragma-attribute-supported-attributes-list.test


Index: clang/test/Misc/pragma-attribute-supported-attributes-list.test
===================================================================
--- clang/test/Misc/pragma-attribute-supported-attributes-list.test
+++ clang/test/Misc/pragma-attribute-supported-attributes-list.test
@@ -115,6 +115,7 @@
 // CHECK-NEXT: NoStackProtector (SubjectMatchRule_function)
 // CHECK-NEXT: NoThreadSafetyAnalysis (SubjectMatchRule_function)
 // CHECK-NEXT: NoThrow (SubjectMatchRule_hasType_functionType)
+// CHECK-NEXT: NoUwtable (SubjectMatchRule_hasType_functionType)
 // CHECK-NEXT: NotTailCalled (SubjectMatchRule_function)
 // CHECK-NEXT: OSConsumed (SubjectMatchRule_variable_is_parameter)
 // CHECK-NEXT: OSReturnsNotRetained (SubjectMatchRule_function, SubjectMatchRule_objc_method, SubjectMatchRule_objc_property, SubjectMatchRule_variable_is_parameter)
Index: clang/test/CodeGen/attr-nouwtable.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/attr-nouwtable.c
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -funwind-tables=2 -S -emit-llvm %s -o - | FileCheck %s
+
+__attribute__((nouwtable))
+int test1(void) { return 0; }
+
+// CHECK: @test1{{.*}}[[ATTR1:#[0-9]+]]
+// CHECK: attributes [[ATTR1]] = {
+// CHECK-NOT: uwtable
+// CHECK: }
Index: clang/lib/CodeGen/CodeGenModule.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenModule.cpp
+++ clang/lib/CodeGen/CodeGenModule.cpp
@@ -1963,7 +1963,7 @@
                                                            llvm::Function *F) {
   llvm::AttrBuilder B(F->getContext());
 
-  if (CodeGenOpts.UnwindTables)
+  if ((!D || !D->hasAttr<NoUwtableAttr>()) && CodeGenOpts.UnwindTables)
     B.addUWTableAttr(llvm::UWTableKind(CodeGenOpts.UnwindTables));
 
   if (CodeGenOpts.StackClashProtector)
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -4537,6 +4537,16 @@
     }];
 }
 
+def NoUwtableDocs : Documentation {
+  let Category = DocCatFunction;
+  let Content = [{
+Clang supports the ``nouwtable`` attribute which skips emitting
+the unwind table entry for the specified function. This attribute is useful for
+selectively emitting the unwind table entry on some functions when building with
+``-funwind-tables`` compiler option.
+    }];
+}
+
 def InternalLinkageDocs : Documentation {
   let Category = DocCatFunction;
   let Content = [{
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -2092,6 +2092,13 @@
   let Documentation = [NoThrowDocs];
 }
 
+def NoUwtable : InheritableAttr {
+  let Spellings = [Clang<"nouwtable">];
+  let Subjects = SubjectList<[FunctionLike]>;
+  let Documentation = [NoUwtableDocs];
+  let SimpleHandler = 1;
+}
+
 def NvWeak : IgnoredAttr {
   // No Declspec spelling of this attribute; the CUDA headers use
   // __attribute__((nv_weak)) unconditionally. Does not receive an [[]]
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -149,6 +149,9 @@
   using the MinGW environment. This attribute is only available for Windows
   targets.
 
+- Introduced a new function attribute ``__attribute__((nouwtable))`` to suppress
+  LLVM IR ``uwtable`` function attribute.
+
 Windows Support
 ---------------
 


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