[PATCH] D56555: Add Attribute to define nonlazy objc classes

[Joe via Phabricator via cfe-commits]

joedaniels29 created this revision.
joedaniels29 added reviewers: erik.pilkington, rjmccall.

Currently to get a nonlazy class in objective c, you need to define a +load method. 
Because we do other work when we realize a class, other than just call that load method, it would be ideal to have an attribute to mark a class as nonlazy. 
libdispatch, libtrace, objc, Foundation all define empty +load methods, simply to make certain classes nonlazy.  This is done during process initialization which causes code pages to be faulted in that shouldn't be and increase the code side working set that is needed only for the sake of creating a process.


Repository:
  rC Clang

https://reviews.llvm.org/D56555

Files:
  clang/include/clang/Basic/Attr.td
  clang/lib/CodeGen/CGObjCMac.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/CodeGenObjC/non-lazy-classes.m


Index: clang/test/CodeGenObjC/non-lazy-classes.m
===================================================================
--- clang/test/CodeGenObjC/non-lazy-classes.m
+++ clang/test/CodeGenObjC/non-lazy-classes.m
@@ -1,6 +1,6 @@
 // RUN: %clang_cc1 -triple x86_64-apple-darwin10 -Wno-objc-root-class -emit-llvm -o - %s | \
 // RUN: FileCheck %s
-// CHECK: @"OBJC_LABEL_NONLAZY_CLASS_$" = private global [1 x {{.*}}] {{.*}}@"OBJC_CLASS_$_A"{{.*}}, section "__DATA,__objc_nlclslist,regular,no_dead_strip", align 8
+// CHECK: @"OBJC_LABEL_NONLAZY_CLASS_$" = private global [2 x {{.*}}]{{.*}}@"OBJC_CLASS_$_A"{{.*}},{{.*}}@"OBJC_CLASS_$_D"{{.*}} section "__DATA,__objc_nlclslist,regular,no_dead_strip", align 8
 // CHECK: @"OBJC_LABEL_NONLAZY_CATEGORY_$" = private global [1 x {{.*}}] {{.*}}@"\01l_OBJC_$_CATEGORY_A_$_Cat"{{.*}}, section "__DATA,__objc_nlcatlist,regular,no_dead_strip", align 8
 
 @interface A @end
@@ -30,3 +30,10 @@
 @interface C : A @end
 @implementation C
 @end
+
+__attribute__((objc_nonlazy_class))
+ at interface D @end
+
+ at implementation D
+ at end
+
Index: clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- clang/lib/Sema/SemaDeclAttr.cpp
+++ clang/lib/Sema/SemaDeclAttr.cpp
@@ -6374,6 +6374,9 @@
   case ParsedAttr::AT_ObjCRootClass:
     handleSimpleAttribute<ObjCRootClassAttr>(S, D, AL);
     break;
+  case ParsedAttr::AT_ObjCNonLazyClass:
+      handleSimpleAttribute<ObjCNonLazyClassAttr>(S, D, AL);
+      break;
   case ParsedAttr::AT_ObjCSubclassingRestricted:
     handleSimpleAttribute<ObjCSubclassingRestrictedAttr>(S, D, AL);
     break;
Index: clang/lib/CodeGen/CGObjCMac.cpp
===================================================================
--- clang/lib/CodeGen/CGObjCMac.cpp
+++ clang/lib/CodeGen/CGObjCMac.cpp
@@ -6255,7 +6255,8 @@
 
 bool
 CGObjCNonFragileABIMac::ImplementationIsNonLazy(const ObjCImplDecl *OD) const {
-  return OD->getClassMethod(GetNullarySelector("load")) != nullptr;
+  return OD->getClassMethod(GetNullarySelector("load")) != nullptr ||
+         OD->getClassInterface()->hasAttr<ObjCNonLazyClassAttr>();
 }
 
 void CGObjCNonFragileABIMac::GetClassSizeInfo(const ObjCImplementationDecl *OID,
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1690,6 +1690,12 @@
   let Documentation = [Undocumented];
 }
 
+def ObjCNonLazyClass : Attr {
+  let Spellings = [Clang<"objc_nonlazy_class">];
+  let Subjects = SubjectList<[ObjCInterface], ErrorDiag>;
+  let Documentation = [Undocumented];
+}
+
 def ObjCSubclassingRestricted : InheritableAttr {
   let Spellings = [Clang<"objc_subclassing_restricted">];
   let Subjects = SubjectList<[ObjCInterface], ErrorDiag>;


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