From f9096e450bb6047ab330c94749f5e80178a62b09 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 14 Dec 2011 19:10:53 +0000
Subject: [PATCH] It turns out that clang does use pointer-to-function types to
 point to ARC-managed pointers sometimes. This fixes rdar://10551239.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@146577 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/ObjCARC.cpp        |  8 ++++--
 test/Transforms/ObjCARC/basic.ll         |  4 ++-
 test/Transforms/ObjCARC/pointer-types.ll | 31 ++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 3 deletions(-)
 create mode 100644 test/Transforms/ObjCARC/pointer-types.ll

diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index ab23884bb04..8e9449f5188 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -179,9 +179,13 @@ static bool IsPotentialUse(const Value *Op) {
         Arg->hasNestAttr() ||
         Arg->hasStructRetAttr())
       return false;
-  // Only consider values with pointer types, and not function pointers.
+  // Only consider values with pointer types.
+  // It seemes intuitive to exclude function pointer types as well, since
+  // functions are never reference-counted, however clang occasionally
+  // bitcasts reference-counted pointers to function-pointer type
+  // temporarily.
   PointerType *Ty = dyn_cast<PointerType>(Op->getType());
-  if (!Ty || isa<FunctionType>(Ty->getElementType()))
+  if (!Ty)
     return false;
   // Conservatively assume anything else is a potential use.
   return true;
diff --git a/test/Transforms/ObjCARC/basic.ll b/test/Transforms/ObjCARC/basic.ll
index c466fa0e254..44c2602e575 100644
--- a/test/Transforms/ObjCARC/basic.ll
+++ b/test/Transforms/ObjCARC/basic.ll
@@ -1528,9 +1528,11 @@ define void @test52(i8** %zz, i8** %pp) {
 
 ; Like test52, but the pointer has function type, so it's assumed to
 ; be not reference counted.
+; Oops. That's wrong. Clang sometimes uses function types gratuitously.
+; See rdar://10551239.
 
 ; CHECK: define void @test53(
-; CHECK-NOT: @objc_
+; CHECK: @objc_
 ; CHECK: }
 define void @test53(void ()** %zz, i8** %pp) {
   %p = load i8** %pp
diff --git a/test/Transforms/ObjCARC/pointer-types.ll b/test/Transforms/ObjCARC/pointer-types.ll
new file mode 100644
index 00000000000..6abc9398643
--- /dev/null
+++ b/test/Transforms/ObjCARC/pointer-types.ll
@@ -0,0 +1,31 @@
+; RUN: opt -objc-arc -S < %s | FileCheck %s
+
+; Don't hoist @objc_release past a use of its pointer, even
+; if the use has function type, because clang uses function types
+; in dubious ways.
+; rdar://10551239
+
+; CHECK: define void @test0(
+; CHECK: %otherBlock = phi void ()* [ %b1, %if.then ], [ null, %entry ]
+; CHECK-NEXT: call void @use_fptr(void ()* %otherBlock)
+; CHECK-NEXT: %tmp11 = bitcast void ()* %otherBlock to i8*
+; CHECK-NEXT: call void @objc_release(i8* %tmp11)
+
+define void @test0(i1 %tobool, void ()* %b1) {
+entry:
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  br label %if.end
+
+if.end:                                           ; preds = %if.then, %entry
+  %otherBlock = phi void ()* [ %b1, %if.then ], [ null, %entry ]
+  call void @use_fptr(void ()* %otherBlock)
+  %tmp11 = bitcast void ()* %otherBlock to i8*
+  call void @objc_release(i8* %tmp11) nounwind
+  ret void
+}
+
+declare void @use_fptr(void ()*)
+declare void @objc_release(i8*)
+
-- 
2.34.1