[llvm-branch-commits] [clang] release/18.x: [ObjC] Check entire chain of superclasses to determine class layout (PR #84093)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: AtariDreams (AtariDreams)

<details>
<summary>Changes</summary>

Backport of https://github.com/llvm/llvm-project/commit/923ddf65f4e21ec67018cf56e823895de18d83bc

---
Full diff: https://github.com/llvm/llvm-project/pull/84093.diff


2 Files Affected:

- (modified) clang/lib/CodeGen/CGObjCMac.cpp (+14-6) 
- (modified) clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m (+102) 


``````````diff
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 517f7cddebc1a2..be628a909d89be 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -1593,12 +1593,20 @@ class CGObjCNonFragileABIMac : public CGObjCCommonMac {
   }
 
   bool isClassLayoutKnownStatically(const ObjCInterfaceDecl *ID) {
-    // NSObject is a fixed size. If we can see the @implementation of a class
-    // which inherits from NSObject then we know that all it's offsets also must
-    // be fixed. FIXME: Can we do this if see a chain of super classes with
-    // implementations leading to NSObject?
-    return ID->getImplementation() && ID->getSuperClass() &&
-           ID->getSuperClass()->getName() == "NSObject";
+    // Test a class by checking its superclasses up to
+    // its base class if it has one.
+    for (; ID; ID = ID->getSuperClass()) {
+      // The layout of base class NSObject
+      // is guaranteed to be statically known
+      if (ID->getIdentifier()->getName() == "NSObject")
+        return true;
+
+      // If we cannot see the @implementation of a class,
+      // we cannot statically know the class layout.
+      if (!ID->getImplementation())
+        return false;
+    }
+    return false;
   }
 
 public:
diff --git a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
index 788b3220af3067..8d55e6c7d23081 100644
--- a/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
+++ b/clang/test/CodeGenObjC/constant-non-fragile-ivar-offset.m
@@ -1,6 +1,13 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.14.0 -emit-llvm %s -o - | FileCheck %s
 
 // CHECK: @"OBJC_IVAR_$_StaticLayout.static_layout_ivar" = hidden constant i64 20
+// CHECK: @"OBJC_IVAR_$_SuperClass.superClassIvar" = hidden constant i64 20
+// CHECK: @"OBJC_IVAR_$_SuperClass._superClassProperty" = hidden constant i64 24
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar" = constant i64 32
+// CHECK: @"OBJC_IVAR_$_IntermediateClass.intermediateClassIvar2" = constant i64 40
+// CHECK: @"OBJC_IVAR_$_IntermediateClass._intermediateProperty" = hidden constant i64 48
+// CHECK: @"OBJC_IVAR_$_SubClass.subClassIvar" = constant i64 56
+// CHECK: @"OBJC_IVAR_$_SubClass._subClassProperty" = hidden constant i64 64
 // CHECK: @"OBJC_IVAR_$_NotStaticLayout.not_static_layout_ivar" = hidden global i64 12
 
 @interface NSObject {
@@ -14,12 +21,105 @@ @interface StaticLayout : NSObject
 @implementation StaticLayout {
   int static_layout_ivar;
 }
+
+// CHECK-LABEL: define internal void @"\01-[StaticLayout meth]"
 -(void)meth {
   static_layout_ivar = 0;
   // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_StaticLayout
+  // CHECK: getelementptr inbounds i8, ptr %0, i64 20
+}
+ at end
+
+ at interface SuperClass : NSObject
+ at property (nonatomic, assign) int superClassProperty;
+ at end
+
+ at implementation SuperClass {
+  int superClassIvar; // Declare an ivar
+}
+
+// CHECK-LABEL: define internal void @"\01-[SuperClass superClassMethod]"
+- (void)superClassMethod {
+    _superClassProperty = 42;
+    superClassIvar = 10;
+    // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SuperClass
+    // CHECK: getelementptr inbounds i8, ptr %1, i64 20
+}
+
+// Implicitly synthesized method here
+// CHECK-LABEL: define internal i32 @"\01-[SuperClass superClassProperty]"
+// CHECK: getelementptr inbounds i8, ptr %0, i64 24
+
+// CHECK-LABEL: define internal void @"\01-[SuperClass setSuperClassProperty:]"
+// CHECK: getelementptr inbounds i8, ptr %1, i64 24
+ at end
+
+ at interface IntermediateClass : SuperClass {
+    double intermediateClassIvar;
+
+    @protected
+    int intermediateClassIvar2;
+}
+ at property (nonatomic, strong) SuperClass *intermediateProperty;
+ at end
+
+ at implementation IntermediateClass
+ at synthesize intermediateProperty = _intermediateProperty;
+
+// CHECK-LABEL: define internal void @"\01-[IntermediateClass intermediateClassMethod]"
+- (void)intermediateClassMethod {
+    intermediateClassIvar = 3.14;
+    // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+    // CHECK: getelementptr inbounds i8, ptr %0, i64 32
+}
+
+// CHECK-LABEL: define internal void @"\01-[IntermediateClass intermediateClassPropertyMethod]"
+- (void)intermediateClassPropertyMethod {
+    self.intermediateProperty = 0;
+    // CHECK: load ptr, ptr @OBJC_SELECTOR_REFERENCES_
+    // CHECK: call void @objc_msgSend(ptr noundef %0, ptr noundef %1, ptr noundef null)
+}
+
+// CHECK-LABEL: define internal void @"\01-[IntermediateClass intermediateClassPropertyMethodDirect]"
+- (void)intermediateClassPropertyMethodDirect {
+    _intermediateProperty = 0;
+    // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_IntermediateClass._intermediateProperty"
+    // CHECK: getelementptr inbounds i8, ptr %0, i64 48
 }
 @end
 
+ at interface SubClass : IntermediateClass {
+    double subClassIvar;
+}
+ at property (nonatomic, assign) SubClass *subClassProperty;
+ at end
+
+ at implementation SubClass
+
+// CHECK-LABEL: define internal void @"\01-[SubClass subclassVar]"
+- (void)subclassVar {
+    subClassIvar = 6.28;
+    // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SubClass
+    // CHECK: getelementptr inbounds i8, ptr %0, i64 56
+}
+
+// CHECK-LABEL: define internal void @"\01-[SubClass intermediateSubclassVar]"
+-(void)intermediateSubclassVar {
+    intermediateClassIvar = 3.14;
+    // CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_IntermediateClass
+    // CHECK: getelementptr inbounds i8, ptr %0, i64 32
+}
+
+// Implicit synthesized method here:
+// CHECK-LABEL: define internal ptr @"\01-[SubClass subClassProperty]"
+// CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SubClass._subClassProperty"
+// CHECK: getelementptr inbounds i8, ptr %0, i64 64
+
+// CHECK-LABEL: define internal void @"\01-[SubClass setSubClassProperty:]"
+// CHECK-NOT: load i64, ptr @"OBJC_IVAR_$_SubClass._subClassProperty"
+// CHECK: getelementptr inbounds i8, ptr %1, i64 64
+ at end
+
 @interface NotNSObject {
   int these, might, change;
 }
@@ -31,6 +131,8 @@ @interface NotStaticLayout : NotNSObject
 @implementation NotStaticLayout {
   int not_static_layout_ivar;
 }
+
+// CHECK-LABEL: define internal void @"\01-[NotStaticLayout meth]"
 -(void)meth {
   not_static_layout_ivar = 0;
   // CHECK: load i64, ptr @"OBJC_IVAR_$_NotStaticLayout.not_static_layout_ivar

``````````

</details>


https://github.com/llvm/llvm-project/pull/84093