From 6eb969b7c5b5195d7f85b70e2e060eb2989cdc3c Mon Sep 17 00:00:00 2001
From: Pierre Habouzit <phabouzit@apple.com>
Date: Wed, 22 Jan 2020 08:46:54 -0800
Subject: [PATCH] [objc_direct] fix codegen for mismatched Decl/Impl return
 types

For non direct methods, the codegen uses the type of the Implementation.
Because Objective-C rules allow some differences between the Declaration
and Implementation return types, when the Implementation is in this
translation unit, the type of the Implementation should be preferred to
emit the Function over the Declaration.

Radar-Id: rdar://problem/58797748
Signed-off-by: Pierre Habouzit <phabouzit@apple.com>
Differential Revision: https://reviews.llvm.org/D73208
---
 clang/lib/CodeGen/CGObjCMac.cpp                    | 47 +++++++++++++++++-----
 .../test/CodeGenObjC/direct-method-ret-mismatch.m  | 19 +++++++++
 2 files changed, 56 insertions(+), 10 deletions(-)
 create mode 100644 clang/test/CodeGenObjC/direct-method-ret-mismatch.m

diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index f994ec9..547a1f3 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -4032,22 +4032,49 @@ llvm::Function *CGObjCCommonMac::GenerateMethod(const ObjCMethodDecl *OMD,
 llvm::Function *
 CGObjCCommonMac::GenerateDirectMethod(const ObjCMethodDecl *OMD,
                                       const ObjCContainerDecl *CD) {
-  auto I = DirectMethodDefinitions.find(OMD->getCanonicalDecl());
-  if (I != DirectMethodDefinitions.end())
-    return I->second;
+  auto *COMD = OMD->getCanonicalDecl();
+  auto I = DirectMethodDefinitions.find(COMD);
+  llvm::Function *OldFn = nullptr, *Fn = nullptr;
 
-  SmallString<256> Name;
-  GetNameForMethod(OMD, CD, Name, /*ignoreCategoryNamespace*/true);
+  if (I != DirectMethodDefinitions.end()) {
+    // Objective-C allows for the declaration and implementation types
+    // to differ slightly.
+    //
+    // If we're being asked for the Function associated for a method
+    // implementation, a previous value might have been cached
+    // based on the type of the canonical declaration.
+    //
+    // If these do not match, then we'll replace this function with
+    // a new one that has the proper type below.
+    if (!OMD->getBody() || COMD->getReturnType() == OMD->getReturnType())
+      return I->second;
+    OldFn = I->second;
+  }
 
   CodeGenTypes &Types = CGM.getTypes();
   llvm::FunctionType *MethodTy =
     Types.GetFunctionType(Types.arrangeObjCMethodDeclaration(OMD));
-  llvm::Function *Method =
-      llvm::Function::Create(MethodTy, llvm::GlobalValue::ExternalLinkage,
-                             Name.str(), &CGM.getModule());
-  DirectMethodDefinitions.insert(std::make_pair(OMD->getCanonicalDecl(), Method));
 
-  return Method;
+  if (OldFn) {
+    Fn = llvm::Function::Create(MethodTy, llvm::GlobalValue::ExternalLinkage,
+                                "", &CGM.getModule());
+    Fn->takeName(OldFn);
+    OldFn->replaceAllUsesWith(
+        llvm::ConstantExpr::getBitCast(Fn, OldFn->getType()));
+    OldFn->eraseFromParent();
+
+    // Replace the cached function in the map.
+    I->second = Fn;
+  } else {
+    SmallString<256> Name;
+    GetNameForMethod(OMD, CD, Name, /*ignoreCategoryNamespace*/ true);
+
+    Fn = llvm::Function::Create(MethodTy, llvm::GlobalValue::ExternalLinkage,
+                                Name.str(), &CGM.getModule());
+    DirectMethodDefinitions.insert(std::make_pair(COMD, Fn));
+  }
+
+  return Fn;
 }
 
 void CGObjCCommonMac::GenerateDirectMethodPrologue(
diff --git a/clang/test/CodeGenObjC/direct-method-ret-mismatch.m b/clang/test/CodeGenObjC/direct-method-ret-mismatch.m
new file mode 100644
index 0000000..65b253d
--- /dev/null
+++ b/clang/test/CodeGenObjC/direct-method-ret-mismatch.m
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -emit-llvm -fobjc-arc -triple x86_64-apple-darwin10 %s -o - | FileCheck %s
+
+__attribute__((objc_root_class))
+@interface Root
+- (Root *)method __attribute__((objc_direct));
+@end
+
+@implementation Root
+// CHECK-LABEL: define internal i8* @"\01-[Root something]"(
+- (id)something {
+  // CHECK: %{{[^ ]*}} = call {{.*}} @"\01-[Root method]"
+  return [self method];
+}
+
+// CHECK-LABEL: define hidden i8* @"\01-[Root method]"(
+- (id)method {
+  return self;
+}
+@end
-- 
2.7.4