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KeyPaths: Take a bit for encoding "let"-ness of stored properties.

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If we know a key path component can be accessed as a stored property, then we should also know whether it's a `let` or not, so it should be safe to encode this in the key path pattern. Stage this change in by changing the number of bits used to store in-line offsets, fixing up the parts of the key path implementation that assumed that it took up the entire payload bitfield.
This commit is contained in:
Joe Groff
2018-08-16 13:17:28 -07:00
parent c11aacc576
commit 00b50ce6ab
7 changed files with 73 additions and 47 deletions
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51
stdlib/public/core/KeyPath.swift
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@@ -758,6 +758,9 @@ internal struct RawKeyPathComponent {
internal static var endOfReferencePrefixFlag: UInt32 {
return _SwiftKeyPathComponentHeader_EndOfReferencePrefixFlag
}
internal static var storedOffsetPayloadMask: UInt32 {
return _SwiftKeyPathComponentHeader_StoredOffsetPayloadMask
}
internal static var outOfLineOffsetPayload: UInt32 {
return _SwiftKeyPathComponentHeader_OutOfLineOffsetPayload
}
@@ -852,6 +855,20 @@ internal struct RawKeyPathComponent {
_value = _value & ~Header.payloadMask | newValue
}
}
internal var storedOffsetPayload: UInt32 {
get {
_sanityCheck(kind == .struct || kind == .class,
"not a stored component")
return _value & Header.storedOffsetPayloadMask
}
set {
_sanityCheck(kind == .struct || kind == .class,
"not a stored component")
_sanityCheck(newValue & Header.storedOffsetPayloadMask == newValue,
"payload too big")
_value = _value & ~Header.storedOffsetPayloadMask | newValue
}
}
internal var endOfReferencePrefix: Bool {
get {
return _value & Header.endOfReferencePrefixFlag != 0
@@ -913,12 +930,12 @@ internal struct RawKeyPathComponent {
internal func _componentBodySize(forPropertyDescriptor: Bool) -> Int {
switch kind {
case .struct, .class:
if payload == Header.unresolvedFieldOffsetPayload
|| payload == Header.outOfLineOffsetPayload {
if storedOffsetPayload == Header.unresolvedFieldOffsetPayload
|| storedOffsetPayload == Header.outOfLineOffsetPayload {
// A 32-bit offset is stored in the body.
return MemoryLayout<UInt32>.size
}
if payload == Header.unresolvedIndirectOffsetPayload {
if storedOffsetPayload == Header.unresolvedIndirectOffsetPayload {
// A pointer-aligned, pointer-sized pointer is stored in the body.
return Header.pointerAlignmentSkew + MemoryLayout<Int>.size
}
@@ -959,7 +976,9 @@ internal struct RawKeyPathComponent {
let ptrSize = MemoryLayout<Int>.size
switch header.kind {
case .struct, .class:
if header.payload == Header.payloadMask { return 4 } // overflowed
if header.storedOffsetPayload == Header.outOfLineOffsetPayload {
return 4 // overflowed
}
return 0
case .external:
// align to pointer + pointer to external descriptor
@@ -993,13 +1012,13 @@ internal struct RawKeyPathComponent {
"no offset for this kind")
// An offset too large to fit inline is represented by a signal and stored
// in the body.
if header.payload == Header.outOfLineOffsetPayload {
if header.storedOffsetPayload == Header.outOfLineOffsetPayload {
// Offset overflowed into body
_sanityCheck(body.count >= MemoryLayout<UInt32>.size,
"component not big enough")
return Int(body.load(as: UInt32.self))
}
return Int(header.payload)
return Int(header.storedOffsetPayload)
}
internal var _computedIDValue: Int {
@@ -1165,7 +1184,7 @@ internal struct RawKeyPathComponent {
switch header.kind {
case .struct,
.class:
if header.payload == Header.outOfLineOffsetPayload {
if header.storedOffsetPayload == Header.outOfLineOffsetPayload {
let overflowOffset = body.load(as: UInt32.self)
buffer.storeBytes(of: overflowOffset, toByteOffset: 4,
as: UInt32.self)
@@ -2292,11 +2311,11 @@ internal func _getKeyPathClassAndInstanceSizeFromPattern(
// reassigned.
// Check the final instantiated size of the offset.
if header.payload == RawKeyPathComponent.Header.unresolvedFieldOffsetPayload
|| header.payload == RawKeyPathComponent.Header.outOfLineOffsetPayload {
if header.storedOffsetPayload == RawKeyPathComponent.Header.unresolvedFieldOffsetPayload
|| header.storedOffsetPayload == RawKeyPathComponent.Header.outOfLineOffsetPayload {
_ = buffer.pop(UInt32.self)
}
if header.payload == RawKeyPathComponent.Header.unresolvedIndirectOffsetPayload {
if header.storedOffsetPayload == RawKeyPathComponent.Header.unresolvedIndirectOffsetPayload {
_ = buffer.pop(Int.self)
// On 64-bit systems the pointer to the ivar offset variable is
// pointer-sized and -aligned, but the resulting offset ought to be
@@ -2363,7 +2382,7 @@ internal func _getKeyPathClassAndInstanceSizeFromPattern(
// The final component will be a stored component with just an offset.
// If the offset requires resolution, then it'll be stored out of
// line after the header.
if descriptorHeader.payload
if descriptorHeader.storedOffsetPayload
> RawKeyPathComponent.Header.maximumOffsetPayload {
newComponentSize = MemoryLayout<RawKeyPathComponent.Header>.size
+ MemoryLayout<UInt32>.size
@@ -2617,7 +2636,7 @@ internal func _instantiateKeyPathBuffer(
func tryToResolveOffset(header: RawKeyPathComponent.Header,
getOutOfLineOffset: () -> UInt32) {
if header.payload == RawKeyPathComponent.Header.unresolvedFieldOffsetPayload {
if header.storedOffsetPayload == RawKeyPathComponent.Header.unresolvedFieldOffsetPayload {
// Look up offset in type metadata. The value in the pattern is the
// offset within the metadata object.
let metadataPtr = unsafeBitCast(base, to: UnsafeRawPointer.self)
@@ -2634,20 +2653,20 @@ internal func _instantiateKeyPathBuffer(
// Rewrite the header for a resolved offset.
var newHeader = header
newHeader.payload = RawKeyPathComponent.Header.outOfLineOffsetPayload
newHeader.storedOffsetPayload = RawKeyPathComponent.Header.outOfLineOffsetPayload
pushDest(newHeader)
pushDest(offset)
return
}
if header.payload == RawKeyPathComponent.Header.unresolvedIndirectOffsetPayload {
if header.storedOffsetPayload == RawKeyPathComponent.Header.unresolvedIndirectOffsetPayload {
// Look up offset in the indirectly-referenced variable we have a
// pointer.
let offsetVar = patternBuffer.pop(UnsafeRawPointer.self)
let offsetValue = UInt32(offsetVar.load(as: UInt.self))
// Rewrite the header for a resolved offset.
var newHeader = header
newHeader.payload = RawKeyPathComponent.Header.outOfLineOffsetPayload
newHeader.storedOffsetPayload = RawKeyPathComponent.Header.outOfLineOffsetPayload
pushDest(newHeader)
pushDest(offsetValue)
return
@@ -2655,7 +2674,7 @@ internal func _instantiateKeyPathBuffer(
// Otherwise, just transfer the pre-resolved component.
pushDest(header)
if header.payload == RawKeyPathComponent.Header.outOfLineOffsetPayload {
if header.storedOffsetPayload == RawKeyPathComponent.Header.outOfLineOffsetPayload {
let offset = getOutOfLineOffset() //patternBuffer.pop(UInt32.self)
pushDest(offset)
}