From 8b74e5afda780d05a46c1a35f46ebfd625e41f1a Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 19 Apr 2012 21:50:46 +0000
Subject: [PATCH] Avoid a bug in the path count computation, preventing an
 infinite loop repeatedlt making the same change. This is for rdar://11256239.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155160 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/ObjCARC.cpp         |  2 +-
 test/Transforms/ObjCARC/split-backedge.ll | 48 +++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/ObjCARC/split-backedge.ll

diff --git a/lib/Transforms/Scalar/ObjCARC.cpp b/lib/Transforms/Scalar/ObjCARC.cpp
index 29234da644f..a5ccfec9a07 100644
--- a/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/lib/Transforms/Scalar/ObjCARC.cpp
@@ -3379,7 +3379,7 @@ ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
 
     // Ok, everything checks out and we're all set. Let's move some code!
     Changed = true;
-    AnyPairsCompletelyEliminated = NewCount == 0;
+    AnyPairsCompletelyEliminated = OldCount != 0 && NewCount == 0;
     NumRRs += OldCount - NewCount;
     MoveCalls(Arg, RetainsToMove, ReleasesToMove,
               Retains, Releases, DeadInsts, M);
diff --git a/test/Transforms/ObjCARC/split-backedge.ll b/test/Transforms/ObjCARC/split-backedge.ll
new file mode 100644
index 00000000000..08e2dce1f55
--- /dev/null
+++ b/test/Transforms/ObjCARC/split-backedge.ll
@@ -0,0 +1,48 @@
+; RUN: opt -S -objc-arc < %s | FileCheck %s
+
+; Handle a retain+release pair entirely contained within a split loop backedge.
+; rdar://11256239
+
+; CHECK: define void @test0
+; CHECK: call i8* @objc_retain(i8* %call) nounwind
+; CHECK: call i8* @objc_retain(i8* %call) nounwind
+; CHECK: call i8* @objc_retain(i8* %cond) nounwind
+; CHECK: call void @objc_release(i8* %call) nounwind
+; CHECK: call void @objc_release(i8* %call) nounwind
+; CHECK: call void @objc_release(i8* %cond) nounwind
+define void @test0() {
+entry:
+  br label %while.body
+
+while.body:                                       ; preds = %while.cond
+  %call = invoke i8* @returner()
+          to label %invoke.cont unwind label %lpad, !clang.arc.no_objc_arc_exceptions !0
+
+invoke.cont:                                      ; preds = %while.body
+  %t0 = call i8* @objc_retain(i8* %call) nounwind
+  %t1 = call i8* @objc_retain(i8* %call) nounwind
+  %call.i1 = invoke i8* @returner()
+          to label %invoke.cont1 unwind label %lpad
+
+invoke.cont1:                                     ; preds = %invoke.cont
+  %cond = select i1 undef, i8* null, i8* %call
+  %t2 = call i8* @objc_retain(i8* %cond) nounwind
+  call void @objc_release(i8* %call) nounwind
+  call void @objc_release(i8* %call) nounwind
+  call void @use_pointer(i8* %cond)
+  call void @objc_release(i8* %cond) nounwind
+  br label %while.body
+
+lpad:                                             ; preds = %invoke.cont, %while.body
+  %t4 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__objc_personality_v0 to i8*)
+          catch i8* null
+  ret void
+}
+
+declare i8* @returner()
+declare i32 @__objc_personality_v0(...)
+declare void @objc_release(i8*)
+declare i8* @objc_retain(i8*)
+declare void @use_pointer(i8*)
+
+!0 = metadata !{}
-- 
2.11.0