Merge pull request #11986 from aschwaighofer/return_dest_from_retain

runtime: return the argument from swift_retain family of functions

Author: aschwaighofer

include/swift/Runtime/Config.h

@@ -190,6 +190,15 @@
 
 #endif
 
+// The runtime implementation uses the preserve_most convention to save
+// registers spills on the hot path.
+#if __has_attribute(preserve_most) &&                                          \
+    (defined(__aarch64__) || defined(__x86_64__))
+#define SWIFT_CC_PreserveMost __attribute__((preserve_most))
+#else
+#define SWIFT_CC_PreserveMost
+#endif
+
 // Generates a name of the runtime entry's implementation by
 // adding an underscore as a prefix and a suffix.
 #define SWIFT_RT_ENTRY_IMPL(Name) _##Name##_

include/swift/Runtime/HeapObject.h

@@ -204,6 +204,10 @@ void swift_slowDealloc(void *ptr, size_t bytes, size_t alignMask)
 ///
 /// \param object - may be null, in which case this is a no-op
 ///
+/// \return object - we return the object because this enables tail call
+/// optimization and the argument register to be live through the call on
+/// architectures whose argument and return register is the same register.
+///
 /// POSSIBILITIES: We may end up wanting a bunch of different variants:
 ///  - the general version which correctly handles null values, swift
 ///     objects, and ObjC objects
@@ -213,34 +217,35 @@ void swift_slowDealloc(void *ptr, size_t bytes, size_t alignMask)
 /// It may also prove worthwhile to have this use a custom CC
 /// which preserves a larger set of registers.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_retain(HeapObject *object)
+HeapObject *swift_retain(HeapObject *object)
     SWIFT_CC(RegisterPreservingCC);
 
 SWIFT_RUNTIME_EXPORT
-void (*SWIFT_CC(RegisterPreservingCC) _swift_retain)(HeapObject *object);
+HeapObject *(*SWIFT_CC(RegisterPreservingCC) _swift_retain)(HeapObject *object);
 
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_retain_n(HeapObject *object, uint32_t n)
+HeapObject *swift_retain_n(HeapObject *object, uint32_t n)
     SWIFT_CC(RegisterPreservingCC);
 
 SWIFT_RUNTIME_EXPORT
-void (*SWIFT_CC(RegisterPreservingCC) _swift_retain_n)(HeapObject *object,
-                                                       uint32_t n);
+HeapObject *(*SWIFT_CC(RegisterPreservingCC)
+                 _swift_retain_n)(HeapObject *object, uint32_t n);
 
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_nonatomic_retain(HeapObject *object)
+HeapObject *swift_nonatomic_retain(HeapObject *object)
     SWIFT_CC(RegisterPreservingCC);
 
 SWIFT_RUNTIME_EXPORT
-void (*SWIFT_CC(RegisterPreservingCC) _swift_nonatomic_retain)(HeapObject *object);
+HeapObject *(*SWIFT_CC(RegisterPreservingCC)
+                 _swift_nonatomic_retain)(HeapObject *object);
 
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_nonatomic_retain_n(HeapObject *object, uint32_t n)
+HeapObject* swift_nonatomic_retain_n(HeapObject *object, uint32_t n)
     SWIFT_CC(RegisterPreservingCC);
 
 SWIFT_RUNTIME_EXPORT
-void (*SWIFT_CC(RegisterPreservingCC) _swift_nonatomic_retain_n)(HeapObject *object,
-                                                       uint32_t n);
+HeapObject *(*SWIFT_CC(RegisterPreservingCC)
+                 _swift_nonatomic_retain_n)(HeapObject *object, uint32_t n);
 
 /// Atomically increments the reference count of an object, unless it has
 /// already been destroyed. Returns nil if the object is dead.
@@ -525,7 +530,7 @@ struct UnownedReference {
 
 /// Increment the unowned retain count.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_unownedRetain(HeapObject *value)
+HeapObject *swift_unownedRetain(HeapObject *value)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Decrement the unowned retain count.
@@ -535,7 +540,7 @@ void swift_unownedRelease(HeapObject *value)
 
 /// Increment the unowned retain count.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_nonatomic_unownedRetain(HeapObject *value)
+void *swift_nonatomic_unownedRetain(HeapObject *value)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Decrement the unowned retain count.
@@ -545,7 +550,7 @@ void swift_nonatomic_unownedRelease(HeapObject *value)
 
 /// Increment the unowned retain count by n.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_unownedRetain_n(HeapObject *value, int n)
+HeapObject *swift_unownedRetain_n(HeapObject *value, int n)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Decrement the unowned retain count by n.
@@ -555,7 +560,7 @@ void swift_unownedRelease_n(HeapObject *value, int n)
 
 /// Increment the unowned retain count by n.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_nonatomic_unownedRetain_n(HeapObject *value, int n)
+HeapObject *swift_nonatomic_unownedRetain_n(HeapObject *value, int n)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Decrement the unowned retain count by n.
@@ -566,13 +571,13 @@ void swift_nonatomic_unownedRelease_n(HeapObject *value, int n)
 /// Increment the strong retain count of an object, aborting if it has
 /// been deallocated.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_unownedRetainStrong(HeapObject *value)
+HeapObject *swift_unownedRetainStrong(HeapObject *value)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Increment the strong retain count of an object, aborting if it has
 /// been deallocated.
 SWIFT_RT_ENTRY_VISIBILITY
-void swift_nonatomic_unownedRetainStrong(HeapObject *value)
+HeapObject *swift_nonatomic_unownedRetainStrong(HeapObject *value)
     SWIFT_CC(RegisterPreservingCC);
 
 /// Increment the strong retain count of an object which may have been
@@ -770,46 +775,46 @@ void *swift_nonatomic_bridgeObjectRetain_n(void *value, int n)
 /// Increment the strong retain count of an object which might not be a native
 /// Swift object.
 SWIFT_RUNTIME_EXPORT
-void swift_unknownRetain(void *value)
+void *swift_unknownRetain(void *value)
     SWIFT_CC(DefaultCC);
 /// Increment the strong retain count of an object which might not be a native
 /// Swift object by n.
 SWIFT_RUNTIME_EXPORT
-void swift_unknownRetain_n(void *value, int n)
+void *swift_unknownRetain_n(void *value, int n)
     SWIFT_CC(DefaultCC);
 
 /// Increment the strong retain count of an object which might not be a native
 /// Swift object.
 SWIFT_RUNTIME_EXPORT
-void swift_nonatomic_unknownRetain(void *value)
+void *swift_nonatomic_unknownRetain(void *value)
     SWIFT_CC(DefaultCC);
 /// Increment the strong retain count of an object which might not be a native
 /// Swift object by n.
 SWIFT_RUNTIME_EXPORT
-void swift_nonatomic_unknownRetain_n(void *value, int n)
+void *swift_nonatomic_unknownRetain_n(void *value, int n)
     SWIFT_CC(DefaultCC);
 
 
 #else
 
-static inline void swift_unknownRetain(void *value)
+static inline void *swift_unknownRetain(void *value)
     SWIFT_CC(DefaultCC) {
-  swift_retain(static_cast<HeapObject *>(value));
+  return swift_retain(static_cast<HeapObject *>(value));
 }
 
-static inline void swift_unknownRetain_n(void *value, int n)
+static inline void *swift_unknownRetain_n(void *value, int n)
     SWIFT_CC(DefaultCC) {
-  swift_retain_n(static_cast<HeapObject *>(value), n);
+  return swift_retain_n(static_cast<HeapObject *>(value), n);
 }
 
-static inline void swift_nonatomic_unknownRetain(void *value)
+static inline void *swift_nonatomic_unknownRetain(void *value)
     SWIFT_CC(DefaultCC) {
-  swift_nonatomic_retain(static_cast<HeapObject *>(value));
+  return swift_nonatomic_retain(static_cast<HeapObject *>(value));
 }
 
-static inline void swift_nonatomic_unknownRetain_n(void *value, int n)
+static inline void *swift_nonatomic_unknownRetain_n(void *value, int n)
     SWIFT_CC(DefaultCC) {
-  swift_nonatomic_retain_n(static_cast<HeapObject *>(value), n);
+  return swift_nonatomic_retain_n(static_cast<HeapObject *>(value), n);
 }
 
 

include/swift/Runtime/InstrumentsSupport.h

@@ -29,11 +29,11 @@ SWIFT_RUNTIME_EXPORT
 BoxPair::Return (*_swift_allocBox)(Metadata const *type);
 
 SWIFT_RUNTIME_EXPORT
-void (*_swift_retain)(HeapObject *object);
+HeapObject *(*_swift_retain)(HeapObject *object);
 SWIFT_RUNTIME_EXPORT
-void (*_swift_retain_n)(HeapObject *object, uint32_t n);
+HeapObject *(*_swift_retain_n)(HeapObject *object, uint32_t n);
 SWIFT_RUNTIME_EXPORT
-void (*_swift_nonatomic_retain)(HeapObject *object);
+HeapObject *(*_swift_nonatomic_retain)(HeapObject *object);
 SWIFT_RUNTIME_EXPORT
 HeapObject *(*_swift_tryRetain)(HeapObject *object);
 SWIFT_RUNTIME_EXPORT