From 09266e4af04ec2dc3a3afc19a3f9d5658d482a44 Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@apple.com>
Date: Thu, 12 Nov 2020 18:33:29 -0800
Subject: [PATCH] [ObjC][ARC] Clear the lists of basic blocks and instructions
 before continuing the loop

This fixes a bug introduced in c6f1713c46e61bbb8ece9ac5ac329d02e7f93228.
---
 llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp |  5 ++++-
 llvm/test/Transforms/ObjCARC/rv.ll          | 25 +++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
index a2dfd1d3d4a0..1cd79875df65 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCOpts.cpp
@@ -2358,8 +2358,11 @@ void ObjCARCOpt::OptimizeReturns(Function &F) {
     if (HasSafePathToCall &&
         GetBasicARCInstKind(Retain) == ARCInstKind::RetainRV &&
         GetBasicARCInstKind(Autorelease) == ARCInstKind::AutoreleaseRV &&
-        !cast<CallInst>(*DependingInstructions.begin())->isTailCall())
+        !cast<CallInst>(*DependingInstructions.begin())->isTailCall()) {
+      DependingInstructions.clear();
+      Visited.clear();
       continue;
+    }
 
     DependingInstructions.clear();
     Visited.clear();
diff --git a/llvm/test/Transforms/ObjCARC/rv.ll b/llvm/test/Transforms/ObjCARC/rv.ll
index 0a1f4665afc6..f89e9f7e39d9 100644
--- a/llvm/test/Transforms/ObjCARC/rv.ll
+++ b/llvm/test/Transforms/ObjCARC/rv.ll
@@ -427,6 +427,31 @@ lpad:
   resume { i8*, i32 } %4
 }
 
+; The second retainRV/autoreleaseRV pair can be removed since the call to
+; @returner is a tail call.
+
+; CHECK-LABEL: define i8* @test30(
+; CHECK: %[[V0:.*]] = call i8* @returner()
+; CHECK-NEXT: call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %[[V0]])
+; CHECK-NEXT: call i8* @llvm.objc.autoreleaseReturnValue(i8* %[[V0]])
+; CHECK-NEXT: ret i8* %[[V0]]
+; CHECK: %[[V3:.*]] = tail call i8* @returner()
+; CHECK-NEXT: ret i8* %[[V3]]
+
+define i8* @test30(i1 %cond) {
+  br i1 %cond, label %bb0, label %bb1
+bb0:
+  %v0 = call i8* @returner()
+  %v1 = call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %v0)
+  %v2 = call i8* @llvm.objc.autoreleaseReturnValue(i8* %v0)
+  ret i8* %v0
+bb1:
+  %v3 = tail call i8* @returner()
+  %v4 = call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %v3)
+  %v5 = call i8* @llvm.objc.autoreleaseReturnValue(i8* %v3)
+  ret i8* %v3
+}
+
 !0 = !{}
 
 ; CHECK: attributes [[NUW]] = { nounwind }