averello/swift-mirror
1
0
Fork 0
mirror of https://github.com/apple/swift.git synced 2025-12-21 12:14:44 +01:00
Code Issues Packages Projects Releases Wiki Activity

Add a Builtin.BridgeObject type.

Browse Source 
This is a type that has ownership of a reference while allowing access to the
spare bits inside the pointer, but which can also safely hold an ObjC tagged pointer
reference (with no spare bits of course). It additionally blesses one
Foundation-coordinated bit with the meaning of "has swift refcounting" in order
to get a faster short-circuit to native refcounting. It supports the following
builtin operations:

- Builtin.castToBridgeObject<T>(ref: T, bits: Builtin.Word) ->
  Builtin.BridgeObject

  Creates a BridgeObject that contains the bitwise-OR of the bit patterns of
  "ref" and "bits". It is the user's responsibility to ensure "bits" doesn't
  interfere with the reference identity of the resulting value. In other words,
  it is undefined behavior unless:

    castReferenceFromBridgeObject(castToBridgeObject(ref, bits)) === ref

  This means "bits" must be zero if "ref" is a tagged pointer. If "ref" is a real
  object pointer, "bits" must not have any non-spare bits set (unless they're
  already set in the pointer value). The native discriminator bit may only be set
  if the object is Swift-refcounted.

- Builtin.castReferenceFromBridgeObject<T>(bo: Builtin.BridgeObject) -> T

  Extracts the reference from a BridgeObject.

- Builtin.castBitPatternFromBridgeObject(bo: Builtin.BridgeObject) -> Builtin.Word

  Presents the bit pattern of a BridgeObject as a Word.

BridgeObject's bits are set up as follows on the various platforms:

i386, armv7:

  No ObjC tagged pointers
  Swift native refcounting flag bit: 0x0000_0001
  Other available spare bits:        0x0000_0002

x86_64:

  Reserved for ObjC tagged pointers: 0x8000_0000_0000_0001
  Swift native refcounting flag bit: 0x0000_0000_0000_0002
  Other available spare bits:        0x7F00_0000_0000_0004

arm64:

  Reserved for ObjC tagged pointers: 0x8000_0000_0000_0000
  Swift native refcounting flag bit: 0x4000_0000_0000_0000
  Other available spare bits:        0x3F00_0000_0000_0007

TODO: BridgeObject doesn't present any extra inhabitants. It ought to at least provide null as an extra inhabitant for Optional.

Swift SVN r22880
This commit is contained in:
Joe Groff
2014-10-23 00:09:23 +00:00
parent 0b7836bbdf
commit 5a2f48e3be
56 changed files with 1004 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
lib/SILAnalysis/AliasAnalysis.cpp
View File

@@ -418,22 +418,14 @@ static bool typedAccessTBAAMayAlias(SILType LTy, SILType RTy, SILModule &Mod) {
ClassDecl *LTyClass = LTy.getClassOrBoundGenericClass();
// If RTy is a Builtin unknown object address type...
if (RTy.is<BuiltinUnknownObjectType>()) {
// And LTy is a swift class address type, they can not alias since swift
// classes and objective-c classes are allocated differently.
if (LTyClass)
return false;
// Otherwise bail and assume that the two values can alias.
// The Builtin reference types can alias any class instance.
if (RTy.is<BuiltinUnknownObjectType>() && LTyClass)
return true;
}
// If RTy is a Builtin Native Object Type, since Builtin Native Object is the
// root of the class hierarchy, it may alias any class.
if (RTy.is<BuiltinNativeObjectType>() && LTyClass)
return true;
if (RTy.is<BuiltinBridgeObjectType>() && LTyClass)
return true;
// If one type is an aggregate and it contains the other type then the record
// reference may alias the aggregate reference.
if (LTy.aggregateContainsRecord(RTy, Mod) ||