From 8f56846d4f86efc9dccd5b64d569878191dcaaf5 Mon Sep 17 00:00:00 2001
From: Kuba Mracek <mracek@apple.com>
Date: Fri, 14 Apr 2017 00:32:43 +0000
Subject: [PATCH] [ObjC] Fix lifetime markers of loop variable in
 EmitObjCForCollectionStmt

CodeGenFunction::EmitObjCForCollectionStmt currently emits lifetime markers for the loop variable in an inconsistent way:  lifetime.start is emitted before the loop is entered, but lifetime.end is emitted inside the loop.  AddressSanitizer uses these markers to track out-of-scope accesses to local variables, and we get false positives in Obj-C foreach loops (in the 2nd iteration of the loop). The markers of the loop variable need to be either both inside the loop (so that we poison and unpoison the variable in each iteration), or both outside. This patch implements the "both inside" approach.

Differential Revision: https://reviews.llvm.org/D32029

llvm-svn: 300287
---
 clang/lib/CodeGen/CGObjC.cpp            | 7 ++-----
 clang/test/CodeGenObjC/arc-foreach.m    | 6 +++---
 clang/test/CodeGenObjC/arc-ternary-op.m | 2 +-
 3 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index 929bda9..50252d5 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -1469,11 +1469,6 @@ void CodeGenFunction::EmitObjCForCollectionStmt(const ObjCForCollectionStmt &S){
   if (DI)
     DI->EmitLexicalBlockStart(Builder, S.getSourceRange().getBegin());
 
-  // The local variable comes into scope immediately.
-  AutoVarEmission variable = AutoVarEmission::invalid();
-  if (const DeclStmt *SD = dyn_cast<DeclStmt>(S.getElement()))
-    variable = EmitAutoVarAlloca(*cast<VarDecl>(SD->getSingleDecl()));
-
   JumpDest LoopEnd = getJumpDestInCurrentScope("forcoll.end");
 
   // Fast enumeration state.
@@ -1625,8 +1620,10 @@ void CodeGenFunction::EmitObjCForCollectionStmt(const ObjCForCollectionStmt &S){
   bool elementIsVariable;
   LValue elementLValue;
   QualType elementType;
+  AutoVarEmission variable = AutoVarEmission::invalid();
   if (const DeclStmt *SD = dyn_cast<DeclStmt>(S.getElement())) {
     // Initialize the variable, in case it's a __block variable or something.
+    variable = EmitAutoVarAlloca(*cast<VarDecl>(SD->getSingleDecl()));
     EmitAutoVarInit(variable);
 
     const VarDecl* D = cast<VarDecl>(SD->getSingleDecl());
diff --git a/clang/test/CodeGenObjC/arc-foreach.m b/clang/test/CodeGenObjC/arc-foreach.m
index db150e8..be25864 100644
--- a/clang/test/CodeGenObjC/arc-foreach.m
+++ b/clang/test/CodeGenObjC/arc-foreach.m
@@ -24,9 +24,9 @@ void test0(NSArray *array) {
 
 // CHECK-LP64-LABEL:    define void @test0(
 // CHECK-LP64:      [[ARRAY:%.*]] = alloca [[ARRAY_T:%.*]]*,
-// CHECK-LP64-NEXT: [[X:%.*]] = alloca i8*,
 // CHECK-LP64-NEXT: [[STATE:%.*]] = alloca [[STATE_T:%.*]],
 // CHECK-LP64-NEXT: [[BUFFER:%.*]] = alloca [16 x i8*], align 8
+// CHECK-LP64-NEXT: [[X:%.*]] = alloca i8*,
 // CHECK-LP64-NEXT: [[BLOCK:%.*]] = alloca [[BLOCK_T:<{.*}>]],
 
 // Initialize 'array'.
@@ -97,9 +97,9 @@ void test1(NSArray *array) {
 
 // CHECK-LP64-LABEL:    define void @test1(
 // CHECK-LP64:      alloca [[ARRAY_T:%.*]]*,
-// CHECK-LP64-NEXT: [[X:%.*]] = alloca i8*,
 // CHECK-LP64-NEXT: [[STATE:%.*]] = alloca [[STATE_T:%.*]],
 // CHECK-LP64-NEXT: alloca [16 x i8*], align 8
+// CHECK-LP64-NEXT: [[X:%.*]] = alloca i8*,
 // CHECK-LP64-NEXT: [[BLOCK:%.*]] = alloca [[BLOCK_T:<{.*}>]],
 
 // CHECK-LP64:      [[T0:%.*]] = getelementptr inbounds [[STATE_T]], [[STATE_T]]* [[STATE]], i32 0, i32 1
@@ -160,7 +160,7 @@ void test3(NSArray *array) {
 
   // CHECK-LP64-LABEL:    define void @test3(
   // CHECK-LP64:      [[ARRAY:%.*]] = alloca [[ARRAY_T]]*, align 8
-  // CHECK-LP64-NEXT: [[X:%.*]] = alloca i8*, align 8
+  // CHECK-LP64:      [[X:%.*]] = alloca i8*, align 8
   // CHECK-LP64:      [[T0:%.*]] = load i8*, i8** [[X]], align 8
   // CHECK-LP64-NEXT: [[T1:%.*]] = icmp ne i8* [[T0]], null
   // CHECK-LP64-NEXT: br i1 [[T1]],
diff --git a/clang/test/CodeGenObjC/arc-ternary-op.m b/clang/test/CodeGenObjC/arc-ternary-op.m
index 3488d2c..8d2672a 100644
--- a/clang/test/CodeGenObjC/arc-ternary-op.m
+++ b/clang/test/CodeGenObjC/arc-ternary-op.m
@@ -120,9 +120,9 @@ void test2(int cond) {
 
   // CHECK-LABEL:    define void @test2(
   // CHECK:      [[COND:%.*]] = alloca i32,
-  // CHECK:      alloca i8*
   // CHECK:      [[CLEANUP_SAVE:%.*]] = alloca i8*
   // CHECK:      [[RUN_CLEANUP:%.*]] = alloca i1
+  // CHECK:      alloca i8*
   //   Evaluate condition; cleanup disabled by default.
   // CHECK:      [[T0:%.*]] = load i32, i32* [[COND]],
   // CHECK-NEXT: icmp ne i32 [[T0]], 0
-- 
2.7.4