From 27e0666725c6558574cb7a55f8c91e7532e09548 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 29 Sep 2011 22:27:34 +0000
Subject: [PATCH] When eliminating unnecessary retain+autorelease on return
 values, handle the case where the retain is in a different basic block.
 rdar://10210274.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@140815 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/ObjCARC.cpp      |  3 +-
 test/Transforms/ObjCARC/empty-block.ll | 59 ++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/ObjCARC/empty-block.ll

diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 29d0fe6a2e3..da74e9c3ec7 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -3198,7 +3198,8 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
 
         // Check that there is nothing that can affect the reference
         // count between the retain and the call.
-        FindDependencies(CanChangeRetainCount, Arg, BB, Retain,
+        // Note that Retain need not be in BB.
+        FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
                          DependingInstructions, Visited, PA);
         if (DependingInstructions.size() != 1)
           goto next_block;
diff --git a/test/Transforms/ObjCARC/empty-block.ll b/test/Transforms/ObjCARC/empty-block.ll
new file mode 100644
index 00000000000..ca5541365a4
--- /dev/null
+++ b/test/Transforms/ObjCARC/empty-block.ll
@@ -0,0 +1,59 @@
+; RUN: opt -S -objc-arc < %s | FileCheck %s
+; rdar://10210274
+
+%0 = type opaque
+
+declare i8* @objc_retain(i8*)
+
+declare void @objc_release(i8*)
+
+declare i8* @objc_autoreleaseReturnValue(i8*)
+
+; Don't delete the autorelease.
+
+; CHECK: define %0* @test0(
+; CHECK:   @objc_retain
+; CHECK: .lr.ph:
+; CHECK-NOT: @objc_r
+; CHECK: @objc_autoreleaseReturnValue
+; CHECK-NOT: @objc_
+; CHECK: }
+define %0* @test0(%0* %buffer) nounwind {
+  %1 = bitcast %0* %buffer to i8*
+  %2 = tail call i8* @objc_retain(i8* %1) nounwind
+  br i1 undef, label %.lr.ph, label %._crit_edge
+
+.lr.ph:                                           ; preds = %.lr.ph, %0
+  br i1 false, label %.lr.ph, label %._crit_edge
+
+._crit_edge:                                      ; preds = %.lr.ph, %0
+  %3 = tail call i8* @objc_retain(i8* %1) nounwind
+  tail call void @objc_release(i8* %1) nounwind, !clang.imprecise_release !0
+  %4 = tail call i8* @objc_autoreleaseReturnValue(i8* %1) nounwind
+  ret %0* %buffer
+}
+
+; Do delete the autorelease, even with the retain in a different block.
+
+; CHECK: define %0* @test1(
+; CHECK-NOT: @objc
+; CHECK: }
+define %0* @test1() nounwind {
+  %buffer = call %0* @foo()
+  %1 = bitcast %0* %buffer to i8*
+  %2 = tail call i8* @objc_retain(i8* %1) nounwind
+  br i1 undef, label %.lr.ph, label %._crit_edge
+
+.lr.ph:                                           ; preds = %.lr.ph, %0
+  br i1 false, label %.lr.ph, label %._crit_edge
+
+._crit_edge:                                      ; preds = %.lr.ph, %0
+  %3 = tail call i8* @objc_retain(i8* %1) nounwind
+  tail call void @objc_release(i8* %1) nounwind, !clang.imprecise_release !0
+  %4 = tail call i8* @objc_autoreleaseReturnValue(i8* %1) nounwind
+  ret %0* %buffer
+}
+
+declare %0* @foo()
+
+!0 = metadata !{}