Merge pull request swiftlang#16890 from eeckstein/stdlib-perf-changes

Some performance improvements in the stdlib, mainly for small string literals

Author: eeckstein

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -686,20 +686,6 @@ SILInstruction *SILCombiner::visitCondFailInst(CondFailInst *CFI) {
   return nullptr;
 }
 
-static bool isValueToBridgeObjectremovable(ValueToBridgeObjectInst *VTBOI) {
-  SILValue operand = VTBOI->getOperand();
-  // If operand is a struct $UInt (% : $Builtin.), fetch the real source
-  if (auto *SI = dyn_cast<StructInst>(operand)) {
-    assert(SI->SILInstruction::getAllOperands().size() == 1 &&
-           "Expected a single operand");
-    operand = SI->getOperand(0);
-  }
-  if (auto *BI = dyn_cast<BuiltinInst>(operand)) {
-    return (BI->getBuiltinInfo().ID == BuiltinValueKind::StringObjectOr);
-  }
-  return false;
-}
-
 SILInstruction *SILCombiner::visitStrongRetainInst(StrongRetainInst *SRI) {
   // Retain of ThinToThickFunction is a no-op.
   SILValue funcOper = SRI->getOperand();
@@ -718,8 +704,7 @@ SILInstruction *SILCombiner::visitStrongRetainInst(StrongRetainInst *SRI) {
   // builtin "stringObjectOr_Int64" (or to tag the string)
   // value_to_bridge_object (cast the UInt to bridge object)
   if (auto *VTBOI = dyn_cast<ValueToBridgeObjectInst>(SRI->getOperand())) {
-    if (isValueToBridgeObjectremovable(VTBOI))
-      return eraseInstFromFunction(*SRI);
+    return eraseInstFromFunction(*SRI);
   }
 
   // Sometimes in the stdlib due to hand offs, we will see code like:
@@ -1169,8 +1154,7 @@ SILInstruction *SILCombiner::visitStrongReleaseInst(StrongReleaseInst *SRI) {
   // builtin "stringObjectOr_Int64" (or to tag the string)
   // value_to_bridge_object (cast the UInt to bridge object)
   if (auto *VTBOI = dyn_cast<ValueToBridgeObjectInst>(SRI->getOperand())) {
-    if (isValueToBridgeObjectremovable(VTBOI))
-      return eraseInstFromFunction(*SRI);
+    return eraseInstFromFunction(*SRI);
   }
 
   // Release of a classbound existential converted from a class is just a

stdlib/public/core/CMakeLists.txt

@@ -108,7 +108,6 @@ set(SWIFTLIB_ESSENTIAL
   Runtime.swift.gyb
   RuntimeFunctionCounters.swift
   SipHash.swift
-  SentinelCollection.swift
   Sequence.swift
   SequenceAlgorithms.swift
   SequenceWrapper.swift

stdlib/public/core/ExistentialCollection.swift.gyb

@@ -413,6 +413,7 @@ internal final class _${Kind}Box<S : ${Kind}> : _Any${Kind}Box<S.Iterator.Elemen
 {
   internal typealias Element = S.Element
 
+  @inline(__always)
   @inlinable
   internal override func _makeIterator() -> AnyIterator<Element> {
     return AnyIterator(_base.makeIterator())
@@ -710,6 +711,7 @@ extension Any${Kind} {
 %   else:
   /// Returns an iterator over the elements of this collection.
 %   end
+  @inline(__always)
   @inlinable
   public func makeIterator() -> Iterator {
     return _box._makeIterator()

stdlib/public/core/GroupInfo.json

@@ -63,7 +63,6 @@
     "Repeat.swift",
     "Sort.swift",
     "Range.swift",
-    "SentinelCollection.swift",
     "ClosedRange.swift",
     "CollectionOfOne.swift",
     "HeapBuffer.swift",

stdlib/public/core/SentinelCollection.swift

@@ -127,25 +127,30 @@ extension _SmallUTF8String {
 #endif
   }
 
+  @inline(__always)
   @inlinable
+  @effects(readonly)
   public // @testable
   init?(_ codeUnits: UnsafeBufferPointer<UInt8>) {
 #if arch(i386) || arch(arm)
     return nil // Never form small strings on 32-bit
 #else
     let count = codeUnits.count
     guard count <= _SmallUTF8String.capacity else { return nil }
-    self.init()
-    self._withAllUnsafeMutableBytes { rawBufPtr in
-      let rawDst = rawBufPtr.baseAddress._unsafelyUnwrappedUnchecked
-      memcpy_(
-        dst: rawDst.assumingMemoryBound(to: UInt8.self),
-        src: codeUnits.baseAddress._unsafelyUnwrappedUnchecked,
-        count: count
-      )
+
+    let addr = codeUnits.baseAddress._unsafelyUnwrappedUnchecked
+    var high: UInt
+    let lowCount: Int
+    if count > 8 {
+      lowCount = 8
+      high = _bytesToUInt(addr + 8, count &- 8)
+    } else {
+      lowCount = count
+      high = 0
     }
-    _sanityCheck(self.count == 0, "overwrote count early?")
-    self.count = count
+    high |= (UInt(count) &<< (8*15))
+    let low = _bytesToUInt(addr, lowCount)
+    _storage = (low, high)
 
     // FIXME: support transcoding
     if !self.isASCII { return nil }
@@ -169,6 +174,18 @@ extension _SmallUTF8String {
   }
 }
 
+@inline(__always)
+@inlinable
+func _bytesToUInt(_ input: UnsafePointer<UInt8>, _ c: Int) -> UInt {
+  var r: UInt = 0
+  var shift: Int = 0
+  for idx in 0..<c {
+    r = r | (UInt(input[idx]) &<< shift)
+    shift = shift &+ 8
+  }
+  return r
+}
+
 //
 // Small string read interface
 //

stdlib/public/core/SmallString.swift

@@ -231,11 +231,8 @@ extension String {
     decodingCString nullTerminatedCodeUnits: UnsafePointer<Encoding.CodeUnit>,
     as sourceEncoding: Encoding.Type) {
 
-    let codeUnits = _SentinelCollection(
-      UnsafeBufferPointer(_unboundedStartingAt: nullTerminatedCodeUnits),
-      until: _IsZero()
-    )
-    self.init(decoding: codeUnits, as: sourceEncoding)
+    self = String.decodeCString(
+      nullTerminatedCodeUnits, as: sourceEncoding)!.result
   }
 
   /// Calls the given closure with a pointer to the contents of the string,
@@ -737,6 +734,7 @@ extension String : _ExpressibleByBuiltinUTF16StringLiteral {
 }
 
 extension String : _ExpressibleByBuiltinStringLiteral {
+  @inline(__always)
   @inlinable
   @effects(readonly)
   @_semantics("string.makeUTF8")