Merge pull request #36046 from atrick/fix-escape

Fix EscapeAnalysis::mayReleaseContent

Author: atrick

include/swift/SILOptimizer/Analysis/EscapeAnalysis.h

@@ -989,8 +989,13 @@ class EscapeAnalysis : public BottomUpIPAnalysis {
   /// The allocator for the connection graphs in Function2ConGraph.
   llvm::SpecificBumpPtrAllocator<FunctionInfo> Allocator;
 
+  // TODO: Use per-function caches, at least for Resilient types, to use Maximal
+  // expansion.
+
   /// Cache for isPointer().
   PointerKindCache pointerKindCache;
+  /// Cache for checking the aggregate pointerness of class properties.
+  PointerKindCache classPropertiesKindCache;
 
   SILModule *M;
 
@@ -1014,6 +1019,12 @@ class EscapeAnalysis : public BottomUpIPAnalysis {
 
   PointerKind findCachedPointerKind(SILType Ty, const SILFunction &F) const;
 
+  PointerKind findClassPropertiesPointerKind(SILType Ty,
+                                             const SILFunction &F) const;
+
+  PointerKind findCachedClassPropertiesKind(SILType Ty,
+                                            const SILFunction &F) const;
+
   // Returns true if the type \p Ty must be a reference or must transitively
   // contain a reference and no other pointer or address type.
   bool hasReferenceOnly(SILType Ty, const SILFunction &F) const {
@@ -1114,6 +1125,10 @@ class EscapeAnalysis : public BottomUpIPAnalysis {
   bool canEscapeToUsePoint(SILValue value, SILInstruction *usePoint,
                            ConnectionGraph *conGraph);
 
+  /// Common implementation for mayReleaseReferenceContent and
+  /// mayReleaseAddressContent.
+  bool mayReleaseContent(SILValue releasedPtr, SILValue liveAddress);
+
   friend struct ::CGForDotView;
 
 public:
@@ -1163,8 +1178,38 @@ class EscapeAnalysis : public BottomUpIPAnalysis {
   bool canEscapeTo(SILValue V, DestroyValueInst *DVI);
 
   /// Return true if \p releasedReference deinitialization may release memory
-  /// pointed to by \p accessedAddress.
-  bool mayReleaseContent(SILValue releasedReference, SILValue accessedAddress);
+  /// pointed to by \p liveAddress.
+  ///
+  /// This determines whether a direct release of \p releasedReference, such as
+  /// destroy_value or strong_release may release memory pointed to by \p
+  /// liveAddress. It can also be used to determine whether passing a
+  /// reference-type call argument may release \p liveAddress.
+  ///
+  /// This does not distinguish between a call that releases \p
+  /// releasedReference directly, vs. a call that releases one of indirect
+  /// references.The side effects of releasing any object reachable from \p
+  /// releasedReference are a strict subset of the side effects of directly
+  /// releasing the parent reference.
+  bool mayReleaseReferenceContent(SILValue releasedReference,
+                                  SILValue liveAddress) {
+    assert(!releasedReference->getType().isAddress() &&
+           "expected a potentially nontrivial value, not an address");
+    return mayReleaseContent(releasedReference, liveAddress);
+  }
+
+  /// Return true if accessing memory at \p accessedAddress may release memory
+  /// pointed to by \p liveAddress.
+  ///
+  /// This makes sense for determining whether accessing indirect call argument
+  /// \p accessedAddress may release memory pointed to by \p liveAddress.
+  ///
+  /// "Access" to the memory can be any release of a reference pointed to by \p
+  /// accessedAddress, so '@in' and '@inout' are handled the same.
+  bool mayReleaseAddressContent(SILValue accessedAddress,
+                                SILValue liveAddress) {
+    assert(accessedAddress->getType().isAddress() && "expected an address");
+    return mayReleaseContent(accessedAddress, liveAddress);
+  }
 
   /// Returns true if the pointers \p V1 and \p V2 can possibly point to the
   /// same memory.

lib/SILOptimizer/Analysis/AliasAnalysis.cpp

@@ -723,8 +723,18 @@ bool AliasAnalysis::canApplyDecrementRefCount(FullApplySite FAS, SILValue Ptr) {
     if (ArgEffect.mayRelease()) {
       // The function may release this argument, so check if the pointer can
       // escape to it.
-      if (EA->mayReleaseContent(FAS.getArgument(Idx), Ptr))
-        return true;
+      auto arg = FAS.getArgument(Idx);
+      if (arg->getType().isAddress()) {
+        // Handle indirect argument as if they are a release to any references
+        // pointed to by the argument's address.
+        if (EA->mayReleaseAddressContent(arg, Ptr))
+          return true;
+      } else {
+        // Handle direct arguments as if they are a direct release of the
+        // reference (just like a destroy_value).
+        if (EA->mayReleaseReferenceContent(arg, Ptr))
+          return true;
+      }
     }
   }
   return false;
@@ -740,12 +750,18 @@ bool AliasAnalysis::canBuiltinDecrementRefCount(BuiltinInst *BI, SILValue Ptr) {
       continue;
 
     // A builtin can only release an object if it can escape to one of the
-    // builtin's arguments. 'EscapeAnalysis::mayReleaseContent()' expects 'Arg'
-    // to be an owned reference and disallows addresses. Conservatively handle
-    // address type arguments as and conservatively treat all other values
-    // potential owned references.
-    if (Arg->getType().isAddress() || EA->mayReleaseContent(Arg, Ptr))
-      return true;
+    // builtin's arguments.
+    if (Arg->getType().isAddress()) {
+      // Handle indirect argument as if they are a release to any references
+      // pointed to by the argument's address.
+      if (EA->mayReleaseAddressContent(Arg, Ptr))
+        return true;
+    } else {
+      // Handle direct arguments as if they are a direct release of the
+      // reference (just like a destroy_value).
+      if (EA->mayReleaseReferenceContent(Arg, Ptr))
+        return true;
+    }
   }
   return false;
 }
@@ -788,7 +804,7 @@ bool AliasAnalysis::mayValueReleaseInterfereWithInstruction(
   // accessedPointer. Access to any objects beyond the first released refcounted
   // object are irrelevant--they must already have sufficient refcount that they
   // won't be released when releasing Ptr.
-  return EA->mayReleaseContent(releasedReference, accessedPointer);
+  return EA->mayReleaseReferenceContent(releasedReference, accessedPointer);
 }
 
 void AliasAnalysis::initialize(SILPassManager *PM) {