From 03648657c7327175f0e6349fb7a83115a0562d9d Mon Sep 17 00:00:00 2001
From: Ted Kremenek <kremenek@apple.com>
Date: Thu, 3 Jul 2008 22:25:27 +0000
Subject: [PATCH] Fix a bug in the dead stores checker reported in the
 following email:

  http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-July/002157.html

Essentially the observer mechanism in LiveVariables was observing block-level
expressions multiple times, leading to a case where the dead store checker could
see a value as dead when it was really live.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@53115 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/LiveVariables.cpp | 14 ++++++++++---
 test/Analysis/dead-stores.m    | 36 ++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)
 create mode 100644 test/Analysis/dead-stores.m

diff --git a/lib/Analysis/LiveVariables.cpp b/lib/Analysis/LiveVariables.cpp
index 54e2195a77..8f391dc561 100644
--- a/lib/Analysis/LiveVariables.cpp
+++ b/lib/Analysis/LiveVariables.cpp
@@ -133,15 +133,23 @@ public:
 };
       
 void TransferFuncs::Visit(Stmt *S) {
-  if (AD.Observer)
-    AD.Observer->ObserveStmt(S,AD,LiveState);
   
   if (S == getCurrentBlkStmt()) {
+    
+    if (AD.Observer)
+      AD.Observer->ObserveStmt(S,AD,LiveState);
+    
     if (getCFG().isBlkExpr(S)) LiveState(S,AD) = Dead;
     StmtVisitor<TransferFuncs,void>::Visit(S);
   }
-  else if (!getCFG().isBlkExpr(S))
+  else if (!getCFG().isBlkExpr(S)) {
+    
+    if (AD.Observer)
+      AD.Observer->ObserveStmt(S,AD,LiveState);
+    
     StmtVisitor<TransferFuncs,void>::Visit(S);
+    
+  }
   else
     // For block-level expressions, mark that they are live.
     LiveState(S,AD) = Alive;
diff --git a/test/Analysis/dead-stores.m b/test/Analysis/dead-stores.m
new file mode 100644
index 0000000000..f58c2c135f
--- /dev/null
+++ b/test/Analysis/dead-stores.m
@@ -0,0 +1,36 @@
+// RUN: clang -warn-dead-stores -verify %s
+
+typedef signed char BOOL;
+typedef unsigned int NSUInteger;
+typedef struct _NSZone NSZone;
+@class NSInvocation, NSMethodSignature, NSCoder, NSString, NSEnumerator;
+@protocol NSObject  - (BOOL)isEqual:(id)object; @end
+@protocol NSCopying  - (id)copyWithZone:(NSZone *)zone; @end
+@protocol NSCoding  - (void)encodeWithCoder:(NSCoder *)aCoder; @end
+@interface NSObject <NSObject> {} @end
+extern id NSAllocateObject(Class aClass, NSUInteger extraBytes, NSZone *zone);
+@interface NSValue : NSObject <NSCopying, NSCoding>  - (void)getValue:(void *)value; @end
+typedef float CGFloat;
+typedef struct _NSPoint {} NSRange;
+@interface NSValue (NSValueRangeExtensions)  + (NSValue *)valueWithRange:(NSRange)range;
+- (BOOL)containsObject:(id)anObject;
+@end
+@class NSURLAuthenticationChallenge;
+@interface NSResponder : NSObject <NSCoding> {} @end
+@class NSArray, NSDictionary, NSString;
+@interface NSObject (NSKeyValueBindingCreation)
++ (void)exposeBinding:(NSString *)binding;
+- (NSArray *)exposedBindings;
+@end
+extern NSString *NSAlignmentBinding;
+
+// This test case was reported as a false positive due to a bug in the
+// LiveVariables <-> DeadStores interplay.  We should not flag a warning
+// here.  The test case was reported in:
+//  http://lists.cs.uiuc.edu/pipermail/cfe-dev/2008-July/002157.html
+void DeadStoreTest(NSObject *anObject) {
+  NSArray *keys;
+  if ((keys = [anObject exposedBindings]) &&   // no-warning
+      ([keys containsObject:@"name"] && [keys containsObject:@"icon"])) {}
+}
+
-- 
2.40.0