SwiftCompilerSources/SIL: Fix APInt assertion failure on rebranch

The assertion is hit through `TypeValueInst.simplify` when constructing
an integer literal instruction with a negative 64-bit `Swift.Int` and a
bit width of 32 (the target pointer bit width for arm64_32 watchOS).
This happens because we tell the `llvm::APInt` constructor to treat the
input integer as unsigned by default in `getAPInt`, and a negative
64-bit signed integer does not fit into 32 bits when interpreted as
unsigned.

Fix this by flipping the default signedness assumption for the Swift API
and introducing a convenience method for constructing a 1-bit integer
literal instruction, where the correct signedness assumption depends on
whether you want to use 1 or -1 for 'true'.

In the context of using an integer to construct an `llvm::APInt`, there
are 2 other cases where signedness matters that come to mind:
1. A non-decimal integer literal narrower than 64 bits, such as
   `0xABCD`, is used.
2. The desired bit width is >64, since `llvm::APInt` can either
   zero-extend or sign-extend the 64-bit integer it accepts.

Neither of these appear to be exercised in SwiftCompilerSources, and
if we ever do, the caller should be responsible for either (1)
appropriately extending the literal manually, e.g.
`Int(Int16(bitPattern: 0xABCD))`, or (2) passing along the appropriate
signedness.

Author: AnthonyLatsis

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyBeginCOWMutation.swift

@@ -65,8 +65,8 @@ private extension BeginCOWMutationInst {
       return
     }
     let builder = Builder(before: self, location: location, context)
-    let zero = builder.createIntegerLiteral(0, type: uniquenessResult.type);
-    uniquenessResult.uses.replaceAll(with: zero, context)
+    let falseLiteral = builder.createBoolLiteral(false)
+    uniquenessResult.uses.replaceAll(with: falseLiteral, context)
   }
 
   func optimizeEmptyBeginEndPair(_ context: SimplifyContext) -> Bool {

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyBuiltin.swift

@@ -81,7 +81,7 @@ private extension BuiltinInst {
       return
     }
     let builder = Builder(before: self, context)
-    let result = builder.createIntegerLiteral(hasArchetype ? 0 : 1, type: type)
+    let result = builder.createBoolLiteral(!hasArchetype)
     uses.replaceAll(with: result, context)
     context.erase(instruction: self)
   }
@@ -94,7 +94,7 @@ private extension BuiltinInst {
       return
     }
     let builder = Builder(before: self, context)
-    let result = builder.createIntegerLiteral(equal ? 1 : 0, type: type)
+    let result = builder.createBoolLiteral(equal)
 
     uses.replaceAll(with: result, context)
   }
@@ -250,7 +250,7 @@ private extension BuiltinInst {
        operands[0].value.lookThroughScalarCasts is StringLiteralInst
     {
       let builder = Builder(before: self, context)
-      let result = builder.createIntegerLiteral(isEqual ? 0 : 1, type: type)
+      let result = builder.createBoolLiteral(!isEqual)
       uses.replaceAll(with: result, context)
       context.erase(instruction: self)
       return true

SwiftCompilerSources/Sources/Optimizer/InstructionSimplification/SimplifyClassifyBridgeObject.swift

@@ -23,7 +23,7 @@ extension ClassifyBridgeObjectInst : OnoneSimplifiable, SILCombineSimplifiable {
     }
 
     let builder = Builder(before: self, context)
-    let falseLiteral = builder.createIntegerLiteral(0, type: context.getBuiltinIntegerType(bitWidth: 1))
+    let falseLiteral = builder.createBoolLiteral(false)
     let tp = builder.createTuple(type: self.type, elements: [falseLiteral, falseLiteral])
     uses.replaceAll(with: tp, context)
     context.erase(instruction: self)

SwiftCompilerSources/Sources/Optimizer/Utilities/Devirtualization.swift

@@ -288,7 +288,7 @@ private func devirtualize(builtinDestroyArray: BuiltinInst, _ context: some Muta
   let preheaderBuilder = Builder(atEndOf: preheaderBlock, location: builtinDestroyArray.location, context)
   let zero = preheaderBuilder.createIntegerLiteral(0, type: indexType)
   let one = preheaderBuilder.createIntegerLiteral(1, type: indexType)
-  let falseValue = preheaderBuilder.createIntegerLiteral(0, type: boolType)
+  let falseValue = preheaderBuilder.createBoolLiteral(false);
   let baseAddress = preheaderBuilder.createPointerToAddress(pointer: basePointer,
                                                             addressType: elementType.addressType,
                                                             isStrict: true, isInvariant: false)

SwiftCompilerSources/Sources/SIL/Builder.swift

@@ -190,11 +190,21 @@ public struct Builder {
     }
   }
 
-  public func createIntegerLiteral(_ value: Int, type: Type) -> IntegerLiteralInst {
-    let literal = bridged.createIntegerLiteral(type.bridged, value)
+  private func createIntegerLiteral(_ value: Int, type: Type, treatAsSigned: Bool) -> IntegerLiteralInst {
+    let literal = bridged.createIntegerLiteral(type.bridged, value, treatAsSigned)
     return notifyNew(literal.getAs(IntegerLiteralInst.self))
   }
-    
+
+  public func createIntegerLiteral(_ value: Int, type: Type) -> IntegerLiteralInst {
+    createIntegerLiteral(value, type: type, treatAsSigned: true)
+  }
+
+  /// Creates a `Builtin.Int1` integer literal instruction with the given value.
+  public func createBoolLiteral(_ value: Bool) -> IntegerLiteralInst {
+    let boolType = notificationHandler.getBuiltinIntegerType(1).type
+    return createIntegerLiteral(value ? 1 : 0, type: boolType, treatAsSigned: false)
+  }
+
   public func createAllocRef(_ type: Type, isObjC: Bool = false, canAllocOnStack: Bool = false, isBare: Bool = false,
                              tailAllocatedTypes: TypeArray, tailAllocatedCounts: [Value]) -> AllocRefInst {
     return tailAllocatedCounts.withBridgedValues { countsRef in

include/swift/SIL/SILBridging.h

@@ -1197,7 +1197,8 @@ struct BridgedBuilder{
                                           BridgedValueArray arguments) const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedInstruction createCondFail(BridgedValue condition,
                                                                        BridgedStringRef message) const;
-  SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedInstruction createIntegerLiteral(BridgedType type, SwiftInt value) const;
+  SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedInstruction createIntegerLiteral(
+      BridgedType type, SwiftInt value, bool treatAsSigned) const;
 
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedInstruction createAllocRef(BridgedType type,
     bool objc, bool canAllocOnStack, bool isBare,

include/swift/SIL/SILBridgingImpl.h

@@ -2219,9 +2219,11 @@ BridgedInstruction BridgedBuilder::createCondFail(BridgedValue condition, Bridge
                                      message.unbridged())};
 }
 
-BridgedInstruction BridgedBuilder::createIntegerLiteral(BridgedType type, SwiftInt value) const {
-  return {
-      unbridged().createIntegerLiteral(regularLoc(), type.unbridged(), value)};
+BridgedInstruction
+BridgedBuilder::createIntegerLiteral(BridgedType type, SwiftInt value,
+                                     bool treatAsSigned) const {
+  return {unbridged().createIntegerLiteral(regularLoc(), type.unbridged(),
+                                           value, treatAsSigned)};
 }
 
 BridgedInstruction BridgedBuilder::createAllocRef(BridgedType type,