[llvm] f2c7c3c - [ObjC][ARC] Invalidate an entry of UnderlyingObjCPtrCache when the

[Akira Hatanaka via llvm-commits]

Author: Akira Hatanaka
Date: 2021-11-08T14:41:06-08:00
New Revision: f2c7c3c7c7b19e77a2948de3c1dd982bf3840377

URL: https://github.com/llvm/llvm-project/commit/f2c7c3c7c7b19e77a2948de3c1dd982bf3840377
DIFF: https://github.com/llvm/llvm-project/commit/f2c7c3c7c7b19e77a2948de3c1dd982bf3840377.diff

LOG: [ObjC][ARC] Invalidate an entry of UnderlyingObjCPtrCache when the
instruction the key points to is deleted

Use weak value handles for both the key and the value. The entry is
invalid if either value handle is null.

This fixes an assertion failure in BasicAAResult::alias that is caused
by UnderlyingObjCPtrCache returning a wrong value.

I don't have a test case for this patch that fails reliably.

rdar://83984790

Added: 
    

Modified: 
    llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
    llvm/lib/Transforms/ObjCARC/ProvenanceAnalysis.h

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h b/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
index 8402b6465104c..87d2c56331766 100644
--- a/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
+++ b/llvm/include/llvm/Analysis/ObjCARCAnalysisUtils.h
@@ -78,14 +78,17 @@ inline const Value *GetUnderlyingObjCPtr(const Value *V) {
 }
 
 /// A wrapper for GetUnderlyingObjCPtr used for results memoization.
-inline const Value *
-GetUnderlyingObjCPtrCached(const Value *V,
-                           DenseMap<const Value *, WeakTrackingVH> &Cache) {
-  if (auto InCache = Cache.lookup(V))
-    return InCache;
+inline const Value *GetUnderlyingObjCPtrCached(
+    const Value *V,
+    DenseMap<const Value *, std::pair<WeakVH, WeakTrackingVH>> &Cache) {
+  // The entry is invalid if either value handle is null.
+  auto InCache = Cache.lookup(V);
+  if (InCache.first && InCache.second)
+    return InCache.second;
 
   const Value *Computed = GetUnderlyingObjCPtr(V);
-  Cache[V] = const_cast<Value *>(Computed);
+  Cache[V] =
+      std::make_pair(const_cast<Value *>(V), const_cast<Value *>(Computed));
   return Computed;
 }
 

diff  --git a/llvm/lib/Transforms/ObjCARC/ProvenanceAnalysis.h b/llvm/lib/Transforms/ObjCARC/ProvenanceAnalysis.h
index a63e356ce1fc1..6d0a67c91cfaf 100644
--- a/llvm/lib/Transforms/ObjCARC/ProvenanceAnalysis.h
+++ b/llvm/lib/Transforms/ObjCARC/ProvenanceAnalysis.h
@@ -56,7 +56,8 @@ class ProvenanceAnalysis {
 
   CachedResultsTy CachedResults;
 
-  DenseMap<const Value *, WeakTrackingVH> UnderlyingObjCPtrCache;
+  DenseMap<const Value *, std::pair<WeakVH, WeakTrackingVH>>
+      UnderlyingObjCPtrCache;
 
   bool relatedCheck(const Value *A, const Value *B);
   bool relatedSelect(const SelectInst *A, const Value *B);