diff --git a/SwiftCompilerSources/CMakeLists.txt b/SwiftCompilerSources/CMakeLists.txt
index e962132dec5..04204d62bb6 100644
--- a/SwiftCompilerSources/CMakeLists.txt
+++ b/SwiftCompilerSources/CMakeLists.txt
@@ -245,11 +245,8 @@ else()
 #define COMPILED_WITH_SWIFT
 
 #include \"Basic/BasicBridging.h\"
-#include \"AST/ASTBridging.h\"
 #include \"SIL/SILBridging.h\"
 #include \"SILOptimizer/OptimizerBridging.h\"
-
-#include \"Parse/RegexParserBridging.h\"
 ")
   add_custom_command(
     OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/HeaderDependencies.cpp"
diff --git a/SwiftCompilerSources/Package.swift b/SwiftCompilerSources/Package.swift
index 2b0c43fa9b1..8f56bacc3d8 100644
--- a/SwiftCompilerSources/Package.swift
+++ b/SwiftCompilerSources/Package.swift
@@ -67,39 +67,22 @@ let package = Package(
     .library(
       name: "swiftCompilerModules",
       type: .static,
-      targets: ["Basic", "AST", "Parse", "SIL", "Optimizer", "_CompilerRegexParser"]),
+      targets: ["Basic", "SIL", "Optimizer"]),
   ],
   dependencies: [
   ],
   // Note that targets and their dependencies must align with
   // 'SwiftCompilerSources/Sources/CMakeLists.txt'
   targets: [
-    .compilerModuleTarget(
-      name: "_CompilerRegexParser",
-      dependencies: [],
-      path: "_RegexParser_Sources",
-      swiftSettings: [
-        // Workaround until `_CompilerRegexParser` is imported as implementation-only
-        // by `_StringProcessing`.
-        .unsafeFlags([
-          "-Xfrontend",
-          "-disable-implicit-string-processing-module-import"
-        ])]),
     .compilerModuleTarget(
       name: "Basic",
       dependencies: []),
-    .compilerModuleTarget(
-      name: "AST",
-      dependencies: ["Basic"]),
-    .compilerModuleTarget(
-      name: "Parse",
-      dependencies: ["Basic", "AST", "_CompilerRegexParser"]),
     .compilerModuleTarget(
       name: "SIL",
       dependencies: ["Basic"]),
     .compilerModuleTarget(
       name: "Optimizer",
-      dependencies: ["Basic", "SIL", "Parse"]),
+      dependencies: ["Basic", "SIL"]),
   ],
   cxxLanguageStandard: .cxx17
 )
diff --git a/SwiftCompilerSources/Sources/AST/CMakeLists.txt b/SwiftCompilerSources/Sources/AST/CMakeLists.txt
deleted file mode 100644
index 3d814cad0a6..00000000000
--- a/SwiftCompilerSources/Sources/AST/CMakeLists.txt
+++ /dev/null
@@ -1,14 +0,0 @@
-# This source file is part of the Swift.org open source project
-#
-# Copyright (c) 2022 Apple Inc. and the Swift project authors
-# Licensed under Apache License v2.0 with Runtime Library Exception
-#
-# See http://swift.org/LICENSE.txt for license information
-# See http://swift.org/CONTRIBUTORS.txt for Swift project authors
-
-add_swift_compiler_module(AST
-  DEPENDS
-    Basic
-  SOURCES
-    DiagnosticEngine.swift)
-
diff --git a/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift b/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift
deleted file mode 100644
index 3d93ebadc1d..00000000000
--- a/SwiftCompilerSources/Sources/AST/DiagnosticEngine.swift
+++ /dev/null
@@ -1,130 +0,0 @@
-//===--- DiagnosticEngine.swift -------------------------------------------===//
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2022 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
-//
-// See https://swift.org/LICENSE.txt for license information
-// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
-//
-//===----------------------------------------------------------------------===//
-
-import ASTBridging
-
-import Basic
-
-public typealias DiagID = BridgedDiagID
-
-public protocol DiagnosticArgument {
-  func _withBridgedDiagnosticArgument(_ fn: (BridgedDiagnosticArgument) -> Void)
-}
-extension String: DiagnosticArgument {
-  public func _withBridgedDiagnosticArgument(_ fn: (BridgedDiagnosticArgument) -> Void) {
-    _withBridgedStringRef { fn(BridgedDiagnosticArgument($0)) }
-  }
-}
-extension Int: DiagnosticArgument {
-  public func _withBridgedDiagnosticArgument(_ fn: (BridgedDiagnosticArgument) -> Void) {
-    fn(BridgedDiagnosticArgument(self))
-  }
-}
-
-public struct DiagnosticFixIt {
-  public let start: SourceLoc
-  public let byteLength: Int
-  public let text: String
-
-  public init(start: SourceLoc, byteLength: Int, replacement text: String) {
-    self.start = start
-    self.byteLength = byteLength
-    self.text = text
-  }
-
-  func withBridgedDiagnosticFixIt(_ fn: (BridgedDiagnosticFixIt) -> Void) {
-    text._withBridgedStringRef { bridgedTextRef in
-      let bridgedDiagnosticFixIt = BridgedDiagnosticFixIt(
-        start.bridged, UInt32(byteLength),
-        bridgedTextRef)
-      fn(bridgedDiagnosticFixIt)
-    }
-  }
-}
-
-public struct DiagnosticEngine {
-  private let bridged: BridgedDiagnosticEngine
-
-  public init(bridged: BridgedDiagnosticEngine) {
-    self.bridged = bridged
-  }
-  public init?(bridged: BridgedNullableDiagnosticEngine) {
-    guard let raw = bridged.raw else {
-      return nil
-    }
-    self.bridged = BridgedDiagnosticEngine(raw: raw)
-  }
-
-  public func diagnose(_ position: SourceLoc?,
-                       _ id: DiagID,
-                       _ args: [DiagnosticArgument],
-                       highlight: CharSourceRange? = nil,
-                       fixIts: [DiagnosticFixIt] = []) {
-
-    let bridgedSourceLoc: BridgedSourceLoc = position.bridged
-    let highlightStart: BridgedSourceLoc
-    let highlightLength: UInt32
-    if let highlight = highlight {
-      highlightStart = highlight.start.bridged
-      highlightLength = highlight.byteLength
-    } else {
-      highlightStart = BridgedSourceLoc()
-      highlightLength = 0
-    }
-    var bridgedArgs: [BridgedDiagnosticArgument] = []
-    var bridgedFixIts: [BridgedDiagnosticFixIt] = []
-
-    // Build a higher-order function to wrap every 'withBridgedXXX { ... }'
-    // calls, so we don't escape anything from the closure. 'bridgedArgs' and
-    // 'bridgedFixIts' are temporary storage to store bridged values. So they
-    // should not be used after the closure is executed.
- 
-    var closure: () -> Void = {
-      bridgedArgs.withBridgedArrayRef { bridgedArgsRef in
-        bridgedFixIts.withBridgedArrayRef { bridgedFixItsRef in
-          bridged.diagnose(at: bridgedSourceLoc, id, bridgedArgsRef,
-                           highlightAt: highlightStart,
-                           highlightLength: highlightLength,
-                           fixIts: bridgedFixItsRef)
-        }
-      }
-    }
-    // 'reversed()' because the closure should be wrapped in that order.
-    for arg in args.reversed() {
-      closure = { [closure, arg] in
-        arg._withBridgedDiagnosticArgument { bridgedArg in
-          bridgedArgs.append(bridgedArg)
-          closure()
-        }
-      }
-    }
-    // 'reversed()' because the closure should be wrapped in that order.
-    for fixIt in fixIts.reversed() {
-      closure = { [closure, fixIt] in
-        fixIt.withBridgedDiagnosticFixIt { bridgedFixIt in
-          bridgedFixIts.append(bridgedFixIt)
-          closure()
-        }
-      }
-    }
-
-    closure()
-  }
-
-  public func diagnose(_ position: SourceLoc?,
-                       _ id: DiagID,
-                       _ args: DiagnosticArgument...,
-                       highlight: CharSourceRange? = nil,
-                       fixIts: DiagnosticFixIt...) {
-    diagnose(position, id, args, highlight: highlight, fixIts: fixIts)
-  }
-}
diff --git a/SwiftCompilerSources/Sources/Basic/SourceLoc.swift b/SwiftCompilerSources/Sources/Basic/SourceLoc.swift
index 0740ce874a6..7a631452b98 100644
--- a/SwiftCompilerSources/Sources/Basic/SourceLoc.swift
+++ b/SwiftCompilerSources/Sources/Basic/SourceLoc.swift
@@ -10,7 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-import ASTBridging
+import BasicBridging
 
 public struct SourceLoc {
   /// Points into a source file.
diff --git a/SwiftCompilerSources/Sources/CMakeLists.txt b/SwiftCompilerSources/Sources/CMakeLists.txt
index af6900ff8d0..622fa883889 100644
--- a/SwiftCompilerSources/Sources/CMakeLists.txt
+++ b/SwiftCompilerSources/Sources/CMakeLists.txt
@@ -8,11 +8,6 @@
 
 # NOTE: Subdirectories must be added in dependency order.
 
-if(SWIFT_BUILD_REGEX_PARSER_IN_COMPILER)
-  add_subdirectory(_RegexParser)
-endif()
 add_subdirectory(Basic)
-add_subdirectory(AST)
-add_subdirectory(Parse)
 add_subdirectory(SIL)
 add_subdirectory(Optimizer)
diff --git a/SwiftCompilerSources/Sources/Optimizer/CMakeLists.txt b/SwiftCompilerSources/Sources/Optimizer/CMakeLists.txt
index acce165e1ee..48b74e373e1 100644
--- a/SwiftCompilerSources/Sources/Optimizer/CMakeLists.txt
+++ b/SwiftCompilerSources/Sources/Optimizer/CMakeLists.txt
@@ -7,7 +7,7 @@
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
 set(dependencies)
-list(APPEND dependencies Basic SIL Parse)
+list(APPEND dependencies Basic SIL)
 
 add_swift_compiler_module(Optimizer DEPENDS ${dependencies})
 
diff --git a/SwiftCompilerSources/Sources/Optimizer/PassManager/Context.swift b/SwiftCompilerSources/Sources/Optimizer/PassManager/Context.swift
index e8bc2f65339..67e206733ad 100644
--- a/SwiftCompilerSources/Sources/Optimizer/PassManager/Context.swift
+++ b/SwiftCompilerSources/Sources/Optimizer/PassManager/Context.swift
@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import AST
 import SIL
 import OptimizerBridging
 
@@ -41,12 +40,6 @@ extension Context {
   }
 }
 
-extension Context {
-  var diagnosticEngine: DiagnosticEngine {
-    return DiagnosticEngine(bridged: _bridged.getDiagnosticEngine())
-  }
-}
-
 /// A context which allows mutation of a function's SIL.
 protocol MutatingContext : Context {
   // Called by all instruction mutations, including inserted new instructions.
diff --git a/SwiftCompilerSources/Sources/Optimizer/PassManager/PassRegistration.swift b/SwiftCompilerSources/Sources/Optimizer/PassManager/PassRegistration.swift
index b30efe9ae65..77dff2559a7 100644
--- a/SwiftCompilerSources/Sources/Optimizer/PassManager/PassRegistration.swift
+++ b/SwiftCompilerSources/Sources/Optimizer/PassManager/PassRegistration.swift
@@ -12,14 +12,12 @@
 
 import SIL
 import OptimizerBridging
-import Parse
 
 @_cdecl("initializeSwiftModules")
 public func initializeSwiftModules() {
   registerSILClasses()
   registerSwiftAnalyses()
   registerSwiftPasses()
-  initializeSwiftParseModules()
   registerOptimizerTests()
 }
 
diff --git a/SwiftCompilerSources/Sources/Parse/CMakeLists.txt b/SwiftCompilerSources/Sources/Parse/CMakeLists.txt
deleted file mode 100644
index 7e5c1c7d977..00000000000
--- a/SwiftCompilerSources/Sources/Parse/CMakeLists.txt
+++ /dev/null
@@ -1,19 +0,0 @@
-# This source file is part of the Swift.org open source project
-#
-# Copyright (c) 2022 Apple Inc. and the Swift project authors
-# Licensed under Apache License v2.0 with Runtime Library Exception
-#
-# See http://swift.org/LICENSE.txt for license information
-# See http://swift.org/CONTRIBUTORS.txt for Swift project authors
-
-set(dependencies Basic AST)
-if(SWIFT_BUILD_REGEX_PARSER_IN_COMPILER)
-  list(APPEND dependencies _CompilerRegexParser)
-endif()
-
-add_swift_compiler_module(Parse
-  DEPENDS
-    ${dependencies}
-  SOURCES
-    Parse.swift
-    Regex.swift)
diff --git a/SwiftCompilerSources/Sources/Parse/Parse.swift b/SwiftCompilerSources/Sources/Parse/Parse.swift
deleted file mode 100644
index a8a79489fc5..00000000000
--- a/SwiftCompilerSources/Sources/Parse/Parse.swift
+++ /dev/null
@@ -1,16 +0,0 @@
-//===--- Parse.swift - SourceLoc bridiging utilities ------------------===//
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2022 Apple Inc. and the Swift project authors
-// Licensed under Apache License v2.0 with Runtime Library Exception
-//
-// See https://swift.org/LICENSE.txt for license information
-// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
-//
-//===----------------------------------------------------------------------===//
-
-@_cdecl("initializeSwiftParseModules")
-public func initializeSwiftParseModules() {
-  registerRegexParser()
-}
diff --git a/SwiftCompilerSources/Sources/_RegexParser/CMakeLists.txt b/SwiftCompilerSources/Sources/_RegexParser/CMakeLists.txt
deleted file mode 100644
index d202c421e84..00000000000
--- a/SwiftCompilerSources/Sources/_RegexParser/CMakeLists.txt
+++ /dev/null
@@ -1,20 +0,0 @@
-# This source file is part of the Swift.org open source project
-#
-# Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
-# Licensed under Apache License v2.0 with Runtime Library Exception
-#
-# See http://swift.org/LICENSE.txt for license information
-# See http://swift.org/CONTRIBUTORS.txt for Swift project authors
-
-file(GLOB_RECURSE _LIBSWIFT_REGEX_PARSER_SOURCES
-  "${SWIFT_PATH_TO_STRING_PROCESSING_SOURCE}/Sources/_RegexParser/*.swift")
-set(LIBSWIFT_REGEX_PARSER_SOURCES)
-foreach(source ${_LIBSWIFT_REGEX_PARSER_SOURCES})
-  file(TO_CMAKE_PATH "${source}" source)
-  list(APPEND LIBSWIFT_REGEX_PARSER_SOURCES ${source})
-endforeach()
-message(STATUS "Using Experimental String Processing library for libswift _RegexParser (${SWIFT_PATH_TO_STRING_PROCESSING_SOURCE}).")
-
-add_swift_compiler_module(_CompilerRegexParser
-  SOURCES
-  "${LIBSWIFT_REGEX_PARSER_SOURCES}")
diff --git a/SwiftCompilerSources/_RegexParser_Sources b/SwiftCompilerSources/_RegexParser_Sources
deleted file mode 120000
index 8c4799dab65..00000000000
--- a/SwiftCompilerSources/_RegexParser_Sources
+++ /dev/null
@@ -1 +0,0 @@
-../../swift-experimental-string-processing/Sources/_RegexParser
\ No newline at end of file
diff --git a/SwiftCompilerSources/stubs.cpp b/SwiftCompilerSources/stubs.cpp
index 36df93a14d9..075c963152d 100644
--- a/SwiftCompilerSources/stubs.cpp
+++ b/SwiftCompilerSources/stubs.cpp
@@ -13,9 +13,6 @@
 extern "C" {
 
 void initializeSwiftModules();
-void initializeSwiftParseModules();
-
 }
 
 void initializeSwiftModules() {}
-void initializeSwiftParseModules() {}
diff --git a/include/swift/AST/DiagnosticsParse.def b/include/swift/AST/DiagnosticsParse.def
index 84dc1347e6b..a70257be826 100644
--- a/include/swift/AST/DiagnosticsParse.def
+++ b/include/swift/AST/DiagnosticsParse.def
@@ -2073,13 +2073,6 @@ ERROR(expected_closure_literal,none,
 ERROR(expected_multiple_closures_block_rbrace,none,
       "expected '}' at the end of a trailing closures block", ())
 
-//------------------------------------------------------------------------------
-// MARK: diagnostics emitted by Swift libraries
-//------------------------------------------------------------------------------
-
-ERROR(foreign_diagnostic,none,
-      "%0", (StringRef))
-
 //------------------------------------------------------------------------------
 // MARK: macros
 //------------------------------------------------------------------------------
diff --git a/include/swift/Basic/InitializeSwiftModules.h b/include/swift/Basic/InitializeSwiftModules.h
index e627525be03..d7984af4c4e 100644
--- a/include/swift/Basic/InitializeSwiftModules.h
+++ b/include/swift/Basic/InitializeSwiftModules.h
@@ -18,7 +18,6 @@ extern "C" {
 #endif
 
 void initializeSwiftModules();
-void initializeSwiftParseModules();
 
 #ifdef __cplusplus
 }
diff --git a/include/swift/Bridging/ASTGen.h b/include/swift/Bridging/ASTGen.h
index f6a52845c09..f83ea9622ad 100644
--- a/include/swift/Bridging/ASTGen.h
+++ b/include/swift/Bridging/ASTGen.h
@@ -134,6 +134,20 @@ swift::Stmt *_Nullable swift_ASTGen_buildStmt(
     BridgedASTContext astContext, BridgedLegacyParser legacyParser,
     BridgedSourceLoc *_Nonnull endSourceLoc);
 
+// MARK: - Regex parsing
+
+bool swift_ASTGen_lexRegexLiteral(const char *_Nonnull *_Nonnull curPtrPtr,
+                                  const char *_Nonnull bufferEndPtr,
+                                  bool mustBeRegex,
+                                  BridgedNullableDiagnosticEngine diagEngine);
+
+bool swift_ASTGen_parseRegexLiteral(BridgedStringRef inputPtr,
+                                    size_t *_Nonnull versionOut,
+                                    void *_Nonnull UnsafeMutableRawPointer,
+                                    size_t captureStructureSize,
+                                    BridgedSourceLoc diagLoc,
+                                    BridgedDiagnosticEngine diagEngine);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/ASTGen/CMakeLists.txt b/lib/ASTGen/CMakeLists.txt
index cc0ec257acd..1da4b6c04dd 100644
--- a/lib/ASTGen/CMakeLists.txt
+++ b/lib/ASTGen/CMakeLists.txt
@@ -5,6 +5,26 @@ add_pure_swift_host_library(swiftLLVMJSON STATIC EMIT_MODULE
     swiftBasic
 )
 
+set(ASTGen_Swift_dependencies)
+
+# If requested, build the regular expression parser into the compiler itself.
+if(SWIFT_BUILD_REGEX_PARSER_IN_COMPILER)
+  file(GLOB_RECURSE _COMPILER_REGEX_PARSER_SOURCES
+    "${SWIFT_PATH_TO_STRING_PROCESSING_SOURCE}/Sources/_RegexParser/*.swift")
+  set(COMPILER_REGEX_PARSER_SOURCES)
+  foreach(source ${_COMPILER_REGEX_PARSER_SOURCES})
+    file(TO_CMAKE_PATH "${source}" source)
+    list(APPEND COMPILER_REGEX_PARSER_SOURCES ${source})
+  endforeach()
+  message(STATUS "Using Experimental String Processing library for _CompilerRegexParser (${SWIFT_PATH_TO_STRING_PROCESSING_SOURCE}).")
+
+  add_pure_swift_host_library(_CompilerRegexParser STATIC EMIT_MODULE
+    "${COMPILER_REGEX_PARSER_SOURCES}"
+  )
+
+  list(APPEND ASTGen_Swift_dependencies _CompilerRegexParser)
+endif()
+
 add_pure_swift_host_library(swiftASTGen STATIC
   Sources/ASTGen/ASTGen.swift
   Sources/ASTGen/Bridge.swift
@@ -19,6 +39,7 @@ add_pure_swift_host_library(swiftASTGen STATIC
   Sources/ASTGen/ParameterClause.swift
   Sources/ASTGen/Patterns.swift
   Sources/ASTGen/PluginHost.swift
+  Sources/ASTGen/Regex.swift
   Sources/ASTGen/SourceFile.swift
   Sources/ASTGen/SourceManager.swift
   Sources/ASTGen/SourceManager+MacroExpansionContext.swift
@@ -39,6 +60,7 @@ add_pure_swift_host_library(swiftASTGen STATIC
     SwiftSyntaxMacros
     SwiftSyntaxMacroExpansion
     swiftLLVMJSON
+    ${ASTGen_Swift_dependencies}
 )
 
 set(c_include_paths
diff --git a/lib/ASTGen/Package.swift b/lib/ASTGen/Package.swift
index e61b6b4aa70..4d41a0eec0f 100644
--- a/lib/ASTGen/Package.swift
+++ b/lib/ASTGen/Package.swift
@@ -64,6 +64,7 @@ let package = Package(
         .product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
         .product(name: "SwiftSyntaxMacroExpansion", package: "swift-syntax"),
         "swiftLLVMJSON",
+        "_CompilerRegexParser",
       ],
       path: "Sources/ASTGen",
       swiftSettings: swiftSetttings
@@ -74,6 +75,12 @@ let package = Package(
       path: "Sources/LLVMJSON",
       swiftSettings: swiftSetttings
     ),
+    .target(
+      name: "_CompilerRegexParser",
+      dependencies: [],
+      path: "_RegexParser_Sources",
+      swiftSettings: swiftSetttings
+    ),
   ],
   cxxLanguageStandard: .cxx17
 )
diff --git a/lib/ASTGen/Sources/ASTGen/Bridge.swift b/lib/ASTGen/Sources/ASTGen/Bridge.swift
index 69566a097cf..3d095e75289 100644
--- a/lib/ASTGen/Sources/ASTGen/Bridge.swift
+++ b/lib/ASTGen/Sources/ASTGen/Bridge.swift
@@ -81,6 +81,13 @@ extension BridgedSourceRange {
 }
 
 extension String {
+  init(bridged: BridgedStringRef) {
+    self.init(
+      decoding: UnsafeBufferPointer(start: bridged.data, count: bridged.count),
+      as: UTF8.self
+    )
+  }
+
   mutating func withBridgedString<R>(_ body: (BridgedStringRef) throws -> R) rethrows -> R {
     try withUTF8 { buffer in
       try body(BridgedStringRef(data: buffer.baseAddress, count: buffer.count))
diff --git a/SwiftCompilerSources/Sources/Parse/Regex.swift b/lib/ASTGen/Sources/ASTGen/Regex.swift
similarity index 71%
rename from SwiftCompilerSources/Sources/Parse/Regex.swift
rename to lib/ASTGen/Sources/ASTGen/Regex.swift
index 13e53185fd9..573910ada64 100644
--- a/SwiftCompilerSources/Sources/Parse/Regex.swift
+++ b/lib/ASTGen/Sources/ASTGen/Regex.swift
@@ -11,27 +11,22 @@
 //===----------------------------------------------------------------------===//
 
 import _RegexParserBridging
-import AST
-import Basic
+import ASTBridging
+import BasicBridging
 
 #if canImport(_CompilerRegexParser)
 @_spi(CompilerInterface) import _CompilerRegexParser
 
-func registerRegexParser() {
-  Parser_registerRegexLiteralParsingFn(_RegexLiteralParsingFn)
-  Parser_registerRegexLiteralLexingFn(_RegexLiteralLexingFn)
-}
-
 /// Bridging between C++ lexer and swiftCompilerLexRegexLiteral.
 ///
 /// Attempt to lex a regex literal string.
 ///
 /// - Parameters:
-///   - CurPtrPtr: A pointer to the current pointer of lexer, which should be
+///   - curPtrPtr: A pointer to the current pointer of lexer, which should be
 ///                the start of the literal. This will be advanced to the point
 ///                at which the lexer should resume, or will remain the same if
 ///                this is not a regex literal.
-///   - BufferEndPtr: A pointer to the end of the buffer, which should not be
+///   - bufferEndPtr: A pointer to the end of the buffer, which should not be
 ///                   lexed past.
 ///   - mustBeRegex: A bool value whether an error during lexing should be
 ///                  considered a regex literal, or some thing else. If true
@@ -42,12 +37,13 @@ func registerRegexParser() {
 /// - Returns: A bool indicating whether lexing was completely erroneous, and
 ///            cannot be recovered from, or false if there either was no error,
 ///            or there was a recoverable error.
-private func _RegexLiteralLexingFn(
+@_cdecl("swift_ASTGen_lexRegexLiteral")
+public func _RegexLiteralLexingFn(
   _ curPtrPtr: UnsafeMutablePointer<UnsafePointer<CChar>>,
   _ bufferEndPtr: UnsafePointer<CChar>,
-  _ mustBeRegex: CBool,
+  _ mustBeRegex: Bool,
   _ bridgedDiagnosticEngine: BridgedNullableDiagnosticEngine
-) -> /*CompletelyErroneous*/ CBool {
+) -> /*CompletelyErroneous*/ Bool {
   let inputPtr = curPtrPtr.pointee
 
   guard let (resumePtr, error) = swiftCompilerLexRegexLiteral(
@@ -62,9 +58,16 @@ private func _RegexLiteralLexingFn(
 
   if let error = error {
     // Emit diagnostic if diagnostics are enabled.
-    if let diagEngine = DiagnosticEngine(bridged: bridgedDiagnosticEngine) {
-      let startLoc = SourceLoc(bridged: BridgedSourceLoc(raw: error.location))!
-      diagEngine.diagnose(startLoc, .foreign_diagnostic, error.message)
+    if let diagEnginePtr = bridgedDiagnosticEngine.raw {
+      var message = error.message
+      message.withBridgedString { message in
+        BridgedDiagnostic(
+          at: BridgedSourceLoc(raw: error.location),
+          message: message,
+          severity: .error,
+          engine: BridgedDiagnosticEngine(raw: diagEnginePtr)
+        ).finish()
+      }
     }
     return error.completelyErroneous
   }
@@ -74,27 +77,26 @@ private func _RegexLiteralLexingFn(
 /// Bridging between C++ parser and swiftCompilerParseRegexLiteral.
 ///
 /// - Parameters:
-///   - inputPtr: A null-terminated C string.
-///   - errOut: A buffer accepting an error string upon error.
-///   - versionOut: A buffer accepting a regex literal format
-///     version.
+///   - input: Regex literal text.
+///   - versionOut: A buffer accepting a regex literal format version.
 ///   - captureStructureOut: A buffer accepting a byte sequence representing the
 ///     capture structure.
 ///   - captureStructureSize: The size of the capture structure buffer. Must be
-///     greater than or equal to `strlen(inputPtr)`.
+///     greater than or equal to `input.size()`.
 ///   - bridgedDiagnosticBaseLoc: Source location of the start of the literal
 ///   - bridgedDiagnosticEngine: Diagnostic engine to emit diagnostics.
 ///
 /// - Returns: `true` if there was a parse error, `false` otherwise.
+@_cdecl("swift_ASTGen_parseRegexLiteral")
 public func _RegexLiteralParsingFn(
-  _ inputPtr: UnsafePointer<CChar>,
-  _ versionOut: UnsafeMutablePointer<CUnsignedInt>,
+  _ input: BridgedStringRef,
+  _ versionOut: UnsafeMutablePointer<UInt>,
   _ captureStructureOut: UnsafeMutableRawPointer,
-  _ captureStructureSize: CUnsignedInt,
+  _ captureStructureSize: UInt,
   _ bridgedDiagnosticBaseLoc: BridgedSourceLoc,
   _ bridgedDiagnosticEngine: BridgedDiagnosticEngine
 ) -> Bool {
-  let str = String(cString: inputPtr)
+  let str = String(bridged: input)
   let captureBuffer = UnsafeMutableRawBufferPointer(
     start: captureStructureOut, count: Int(captureStructureSize))
   do {
@@ -102,16 +104,23 @@ public func _RegexLiteralParsingFn(
     // For now, it is the same as the input.
     let (_, version) = try swiftCompilerParseRegexLiteral(
       str, captureBufferOut: captureBuffer)
-    versionOut.pointee = CUnsignedInt(version)
+    versionOut.pointee = UInt(version)
     return false
   } catch let error as CompilerParseError {
-    var diagLoc = SourceLoc(bridged: bridgedDiagnosticBaseLoc)
-    let diagEngine = DiagnosticEngine(bridged: bridgedDiagnosticEngine)
-    if let _diagLoc = diagLoc, let errorLoc = error.location {
+    var diagLoc = bridgedDiagnosticBaseLoc
+    if diagLoc.isValid, let errorLoc = error.location {
       let offset = str.utf8.distance(from: str.startIndex, to: errorLoc)
-      diagLoc = _diagLoc.advanced(by: offset)
+      diagLoc = diagLoc.advanced(by: offset)
+    }
+    var message = error.message
+    message.withBridgedString { message in
+      BridgedDiagnostic(
+        at: diagLoc,
+        message: message,
+        severity: .error,
+        engine: bridgedDiagnosticEngine
+      ).finish()
     }
-    diagEngine.diagnose(diagLoc, .foreign_diagnostic, error.message)
     return true
   } catch {
     fatalError("Expected CompilerParseError")
@@ -121,6 +130,5 @@ public func _RegexLiteralParsingFn(
 #else // canImport(_CompilerRegexParser)
 
 #warning("Regex parsing is disabled")
-func registerRegexParser() {}
 
 #endif // canImport(_CompilerRegexParser)
diff --git a/lib/ASTGen/_RegexParser_Sources b/lib/ASTGen/_RegexParser_Sources
new file mode 120000
index 00000000000..b52a98d0897
--- /dev/null
+++ b/lib/ASTGen/_RegexParser_Sources
@@ -0,0 +1 @@
+../../../swift-experimental-string-processing/Sources/_RegexParser
\ No newline at end of file
diff --git a/lib/Parse/CMakeLists.txt b/lib/Parse/CMakeLists.txt
index 0f3aa941851..367a540ee86 100644
--- a/lib/Parse/CMakeLists.txt
+++ b/lib/Parse/CMakeLists.txt
@@ -58,6 +58,13 @@ if (SWIFT_BUILD_SWIFT_SYNTAX)
   )
 endif()
 
+if(SWIFT_BUILD_REGEX_PARSER_IN_COMPILER)
+  target_compile_definitions(swiftParse
+    PRIVATE
+    SWIFT_BUILD_REGEX_PARSER_IN_COMPILER
+  )
+endif()
+
 if(SWIFT_COMPILER_VERSION)
   set_property(SOURCE ParseVersion.cpp APPEND_STRING PROPERTY COMPILE_FLAGS
     " -DSWIFT_COMPILER_VERSION=\"\\\"${SWIFT_COMPILER_VERSION}\\\"\"")
diff --git a/lib/Parse/Lexer.cpp b/lib/Parse/Lexer.cpp
index aa5d9c0f840..dabf5a3241f 100644
--- a/lib/Parse/Lexer.cpp
+++ b/lib/Parse/Lexer.cpp
@@ -19,6 +19,7 @@
 #include "swift/AST/Identifier.h"
 #include "swift/Basic/LangOptions.h"
 #include "swift/Basic/SourceManager.h"
+#include "swift/Bridging/ASTGen.h"
 #include "swift/Parse/Confusables.h"
 #include "swift/Parse/RegexParserBridging.h"
 #include "llvm/ADT/SmallString.h"
@@ -33,12 +34,6 @@
 
 #include <limits>
 
-// Regex lexing delivered via libSwift.
-static RegexLiteralLexingFn regexLiteralLexingFn = nullptr;
-void Parser_registerRegexLiteralLexingFn(RegexLiteralLexingFn fn) {
-  regexLiteralLexingFn = fn;
-}
-
 using namespace swift;
 
 // clang::isAsciiIdentifierStart and clang::isAsciiIdentifierContinue are
@@ -2040,9 +2035,10 @@ bool Lexer::isPotentialUnskippableBareSlashRegexLiteral(const Token &Tok) const
 const char *Lexer::tryScanRegexLiteral(const char *TokStart, bool MustBeRegex,
                                        DiagnosticEngine *Diags,
                                        bool &CompletelyErroneous) const {
+#if SWIFT_BUILD_REGEX_PARSER_IN_COMPILER
   // We need to have experimental string processing enabled, and have the
   // parsing logic for regex literals available.
-  if (!LangOpts.EnableExperimentalStringProcessing || !regexLiteralLexingFn)
+  if (!LangOpts.EnableExperimentalStringProcessing)
     return nullptr;
 
   bool IsForwardSlash = (*TokStart == '/');
@@ -2088,9 +2084,9 @@ const char *Lexer::tryScanRegexLiteral(const char *TokStart, bool MustBeRegex,
   // - Ptr will not be advanced if this is not for a regex literal.
   // - CompletelyErroneous will be set if there was an error that cannot be
   //   recovered from.
-  auto *Ptr = TokStart;
+  const char *Ptr = TokStart;
   CompletelyErroneous =
-      regexLiteralLexingFn(&Ptr, BufferEnd, MustBeRegex, Diags);
+      swift_ASTGen_lexRegexLiteral(&Ptr, BufferEnd, MustBeRegex, Diags);
 
   // If we didn't make any lexing progress, this isn't a regex literal and we
   // should fallback to lexing as something else.
@@ -2178,6 +2174,9 @@ const char *Lexer::tryScanRegexLiteral(const char *TokStart, bool MustBeRegex,
   }
   assert(Ptr > TokStart && Ptr <= BufferEnd);
   return Ptr;
+#else
+  return nullptr;
+#endif
 }
 
 bool Lexer::tryLexRegexLiteral(const char *TokStart) {
diff --git a/lib/Parse/ParseRegex.cpp b/lib/Parse/ParseRegex.cpp
index b42fea1b89d..93b8d8c09c2 100644
--- a/lib/Parse/ParseRegex.cpp
+++ b/lib/Parse/ParseRegex.cpp
@@ -15,35 +15,29 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/AST/DiagnosticsParse.h"
+#include "swift/Bridging/ASTGen.h"
 #include "swift/Parse/Parser.h"
 
-// Regex parser delivered via Swift modules.
-#include "swift/Parse/RegexParserBridging.h"
-static RegexLiteralParsingFn regexLiteralParsingFn = nullptr;
-void Parser_registerRegexLiteralParsingFn(RegexLiteralParsingFn fn) {
-  regexLiteralParsingFn = fn;
-}
-
 using namespace swift;
 
 ParserResult<Expr> Parser::parseExprRegexLiteral() {
   assert(Tok.is(tok::regex_literal));
-  assert(regexLiteralParsingFn);
 
+#if SWIFT_BUILD_REGEX_PARSER_IN_COMPILER
   auto regexText = Tok.getText();
 
   // Let the Swift library parse the contents, returning an error, or null if
   // successful.
-  unsigned version = 0;
+  size_t version = 0;
   auto capturesBuf = Context.AllocateUninitialized<uint8_t>(
       RegexLiteralExpr::getCaptureStructureSerializationAllocationSize(
           regexText.size()));
-  bool hadError = regexLiteralParsingFn(
-      regexText.str().c_str(), &version,
-      /*captureStructureOut*/ capturesBuf.data(),
-      /*captureStructureSize*/ capturesBuf.size(),
-      /*diagBaseLoc*/ {(const uint8_t *)(Tok.getLoc().getOpaquePointerValue())},
-      &Diags);
+  bool hadError = swift_ASTGen_parseRegexLiteral(
+      regexText,
+      /*versionOut=*/&version,
+      /*captureStructureOut=*/capturesBuf.data(),
+      /*captureStructureSize=*/capturesBuf.size(),
+      /*diagBaseLoc=*/Tok.getLoc(), &Diags);
   auto loc = consumeToken();
   SourceMgr.recordRegexLiteralStartLoc(loc);
 
@@ -53,4 +47,7 @@ ParserResult<Expr> Parser::parseExprRegexLiteral() {
   assert(version >= 1);
   return makeParserResult(RegexLiteralExpr::createParsed(
       Context, loc, regexText, version, capturesBuf));
+#else
+  llvm_unreachable("Lexer should not emit tok::regex_literal");
+#endif
 }
diff --git a/test/IDE/complete_regex.swift b/test/IDE/complete_regex.swift
index 587c3b24324..c5da4e05e02 100644
--- a/test/IDE/complete_regex.swift
+++ b/test/IDE/complete_regex.swift
@@ -1,4 +1,4 @@
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-ide-test -enable-bare-slash-regex -batch-code-completion -source-filename %s -filecheck %raw-FileCheck -completion-output-dir %t
diff --git a/test/SourceKit/CodeComplete/rdar95772803.swift b/test/SourceKit/CodeComplete/rdar95772803.swift
index b68bca2571a..eec4f67e38a 100644
--- a/test/SourceKit/CodeComplete/rdar95772803.swift
+++ b/test/SourceKit/CodeComplete/rdar95772803.swift
@@ -11,4 +11,4 @@ var qux: Regex<Substring> { / x}/ }
 // RUN: -req=complete -pos=4:28 %s -- -enable-bare-slash-regex %s == \
 // RUN: -req=complete -pos=5:28 %s -- -enable-bare-slash-regex %s
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
diff --git a/test/StringProcessing/Frontend/enable-flag.swift b/test/StringProcessing/Frontend/enable-flag.swift
index 601cdb71e1a..b1768a913dc 100644
--- a/test/StringProcessing/Frontend/enable-flag.swift
+++ b/test/StringProcessing/Frontend/enable-flag.swift
@@ -2,7 +2,7 @@
 // RUN: %target-typecheck-verify-swift -disable-availability-checking -enable-experimental-string-processing -enable-bare-slash-regex
 // RUN: %target-typecheck-verify-swift -disable-availability-checking -disable-experimental-string-processing -enable-experimental-string-processing -enable-bare-slash-regex
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 prefix operator /
 
diff --git a/test/StringProcessing/Parse/forward-slash-regex-disabled.swift b/test/StringProcessing/Parse/forward-slash-regex-disabled.swift
index 4c491a4a863..db403c97dfe 100644
--- a/test/StringProcessing/Parse/forward-slash-regex-disabled.swift
+++ b/test/StringProcessing/Parse/forward-slash-regex-disabled.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -disable-availability-checking
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 prefix operator /
 prefix operator ^/
diff --git a/test/StringProcessing/Parse/forward-slash-regex-skipping-allowed.swift b/test/StringProcessing/Parse/forward-slash-regex-skipping-allowed.swift
index e9b9c2b122c..1974bd55c60 100644
--- a/test/StringProcessing/Parse/forward-slash-regex-skipping-allowed.swift
+++ b/test/StringProcessing/Parse/forward-slash-regex-skipping-allowed.swift
@@ -4,7 +4,7 @@
 // RUN: %{python} %utils/process-stats-dir.py --set-csv-baseline %t/stats.csv %t
 // RUN: %FileCheck -input-file %t/stats.csv %s
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // Make sure we can skip in all of the below cases.
 
diff --git a/test/StringProcessing/Parse/forward-slash-regex-skipping-invalid.swift b/test/StringProcessing/Parse/forward-slash-regex-skipping-invalid.swift
index ccebc28bee8..23e3e8c16f9 100644
--- a/test/StringProcessing/Parse/forward-slash-regex-skipping-invalid.swift
+++ b/test/StringProcessing/Parse/forward-slash-regex-skipping-invalid.swift
@@ -2,7 +2,7 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -experimental-skip-non-inlinable-function-bodies-without-types
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -experimental-skip-non-inlinable-function-bodies
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // We don't consider this a regex literal when skipping as it has an initial
 // space.
diff --git a/test/StringProcessing/Parse/forward-slash-regex-skipping.swift b/test/StringProcessing/Parse/forward-slash-regex-skipping.swift
index e3e9c9d0704..031bef3a1ef 100644
--- a/test/StringProcessing/Parse/forward-slash-regex-skipping.swift
+++ b/test/StringProcessing/Parse/forward-slash-regex-skipping.swift
@@ -2,7 +2,7 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -experimental-skip-non-inlinable-function-bodies-without-types
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -experimental-skip-non-inlinable-function-bodies
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // Make sure we properly handle `/.../` regex literals in skipped function
 // bodies. Currently we detect them and avoid skipping, but in the future we
diff --git a/test/StringProcessing/Parse/forward-slash-regex.swift b/test/StringProcessing/Parse/forward-slash-regex.swift
index 22c6a654e6d..f4990d4fcb4 100644
--- a/test/StringProcessing/Parse/forward-slash-regex.swift
+++ b/test/StringProcessing/Parse/forward-slash-regex.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -typo-correction-limit 0
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 // REQUIRES: concurrency
 
 prefix operator /
diff --git a/test/StringProcessing/Parse/prefix-slash.swift b/test/StringProcessing/Parse/prefix-slash.swift
index 4be97f55397..dbe33cac8d9 100644
--- a/test/StringProcessing/Parse/prefix-slash.swift
+++ b/test/StringProcessing/Parse/prefix-slash.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // Test the behavior of prefix '/' with regex literals enabled.
 
diff --git a/test/StringProcessing/Parse/regex.swift b/test/StringProcessing/Parse/regex.swift
index 797fc2af85e..a25db9de001 100644
--- a/test/StringProcessing/Parse/regex.swift
+++ b/test/StringProcessing/Parse/regex.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 _ = /abc/
 _ = #/abc/#
diff --git a/test/StringProcessing/Parse/regex_parse_end_of_buffer.swift b/test/StringProcessing/Parse/regex_parse_end_of_buffer.swift
index 5c62181c0c8..a31ddb71b35 100644
--- a/test/StringProcessing/Parse/regex_parse_end_of_buffer.swift
+++ b/test/StringProcessing/Parse/regex_parse_end_of_buffer.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // Note there is purposefully no trailing newline here.
 // expected-error@+2:20 {{unterminated regex literal}}
diff --git a/test/StringProcessing/Parse/regex_parse_error.swift b/test/StringProcessing/Parse/regex_parse_error.swift
index c719e33ad9b..ffa05d1ac9a 100644
--- a/test/StringProcessing/Parse/regex_parse_error.swift
+++ b/test/StringProcessing/Parse/regex_parse_error.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 _ = /(/ // expected-error@:7 {{expected ')'}}
 _ = #/(/# // expected-error@:8 {{expected ')'}}
diff --git a/test/StringProcessing/Runtime/regex_basic.swift b/test/StringProcessing/Runtime/regex_basic.swift
index 9ad6c31d306..498894cd1df 100644
--- a/test/StringProcessing/Runtime/regex_basic.swift
+++ b/test/StringProcessing/Runtime/regex_basic.swift
@@ -1,6 +1,6 @@
 // RUN: %target-run-simple-swift(-Xfrontend -enable-bare-slash-regex)
 
-// REQUIRES: swift_in_compiler,string_processing,executable_test
+// REQUIRES: swift_swift_parser,string_processing,executable_test
 
 import StdlibUnittest
 
diff --git a/test/StringProcessing/SILGen/regex_literal_silgen.swift b/test/StringProcessing/SILGen/regex_literal_silgen.swift
index 7d16c82d810..3cfa2bba161 100644
--- a/test/StringProcessing/SILGen/regex_literal_silgen.swift
+++ b/test/StringProcessing/SILGen/regex_literal_silgen.swift
@@ -1,5 +1,5 @@
 // RUN: %target-swift-frontend -emit-silgen -enable-bare-slash-regex -disable-availability-checking %s | %FileCheck %s
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 var s = #/abc/#
 // CHECK: [[REGEX_STR_LITERAL:%[0-9]+]] = string_literal utf8 "#/abc/#"
diff --git a/test/StringProcessing/Sema/regex_builder_fix_import_after_imports.swift b/test/StringProcessing/Sema/regex_builder_fix_import_after_imports.swift
index 29e7881822a..acaf229511b 100644
--- a/test/StringProcessing/Sema/regex_builder_fix_import_after_imports.swift
+++ b/test/StringProcessing/Sema/regex_builder_fix_import_after_imports.swift
@@ -7,7 +7,7 @@
 
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking -I %t
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 import A
 
diff --git a/test/StringProcessing/Sema/regex_builder_fix_import_decl.swift b/test/StringProcessing/Sema/regex_builder_fix_import_decl.swift
index 31feb674449..a0df60f6cdf 100644
--- a/test/StringProcessing/Sema/regex_builder_fix_import_decl.swift
+++ b/test/StringProcessing/Sema/regex_builder_fix_import_decl.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 struct S {
   func foo() {
diff --git a/test/StringProcessing/Sema/regex_builder_fix_import_top_level.swift b/test/StringProcessing/Sema/regex_builder_fix_import_top_level.swift
index eaae0554689..155b43f50d7 100644
--- a/test/StringProcessing/Sema/regex_builder_fix_import_top_level.swift
+++ b/test/StringProcessing/Sema/regex_builder_fix_import_top_level.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 Regex {} // expected-error {{regex builder requires the 'RegexBuilder' module be imported'}} {{5:1-1=import RegexBuilder\n\n}}
 
diff --git a/test/StringProcessing/Sema/regex_builder_unavailable.swift b/test/StringProcessing/Sema/regex_builder_unavailable.swift
index 38bf6049b31..7167315c87a 100644
--- a/test/StringProcessing/Sema/regex_builder_unavailable.swift
+++ b/test/StringProcessing/Sema/regex_builder_unavailable.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -target %target-cpu-apple-macosx12.0
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 // REQUIRES: OS=macosx
 
 import RegexBuilder
diff --git a/test/StringProcessing/Sema/regex_literal_availability.swift b/test/StringProcessing/Sema/regex_literal_availability.swift
index ec688558767..bcf8cdce2d0 100644
--- a/test/StringProcessing/Sema/regex_literal_availability.swift
+++ b/test/StringProcessing/Sema/regex_literal_availability.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -target %target-cpu-apple-macosx12.0
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 // REQUIRES: OS=macosx
 
 _ = /x/ // expected-error {{'Regex' is only available in}}
diff --git a/test/StringProcessing/Sema/regex_literal_diagnostics.swift b/test/StringProcessing/Sema/regex_literal_diagnostics.swift
index 0a0f0629669..e3ec4b77c70 100644
--- a/test/StringProcessing/Sema/regex_literal_diagnostics.swift
+++ b/test/StringProcessing/Sema/regex_literal_diagnostics.swift
@@ -1,6 +1,6 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
 
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 postfix operator ^^
 postfix func ^^ <T> (_ x: T) -> T { x }
diff --git a/test/StringProcessing/Sema/regex_literal_type_inference.swift b/test/StringProcessing/Sema/regex_literal_type_inference.swift
index 9cce7a1b0e7..5ea94df139e 100644
--- a/test/StringProcessing/Sema/regex_literal_type_inference.swift
+++ b/test/StringProcessing/Sema/regex_literal_type_inference.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -enable-bare-slash-regex -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 let r0 = #/./#
 let _: Regex<Substring> = r0
diff --git a/test/StringProcessing/Sema/string_processing_import.swift b/test/StringProcessing/Sema/string_processing_import.swift
index 5a83931364d..200e0729f8b 100644
--- a/test/StringProcessing/Sema/string_processing_import.swift
+++ b/test/StringProcessing/Sema/string_processing_import.swift
@@ -1,5 +1,5 @@
 // RUN: %target-typecheck-verify-swift -disable-implicit-string-processing-module-import -disable-availability-checking
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 // expected-error @+1 {{missing 'Regex' declaration, probably because the '_StringProcessing' module was not imported properly}}
 let r0 = #/./#
diff --git a/test/stmt/then_stmt.swift b/test/stmt/then_stmt.swift
index 2ce031e2725..ec531f99fff 100644
--- a/test/stmt/then_stmt.swift
+++ b/test/stmt/then_stmt.swift
@@ -4,7 +4,7 @@
 // REQUIRES: asserts
 
 // Required for regex
-// REQUIRES: swift_in_compiler
+// REQUIRES: swift_swift_parser
 
 func then(_: Int = 0, x: Int = 0, fn: () -> Void = {}) {}
 
diff --git a/tools/libSwiftScan/libSwiftScan.cpp b/tools/libSwiftScan/libSwiftScan.cpp
index 8afd331b4dd..d1377cbcca3 100644
--- a/tools/libSwiftScan/libSwiftScan.cpp
+++ b/tools/libSwiftScan/libSwiftScan.cpp
@@ -14,7 +14,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "swift/Basic/InitializeSwiftModules.h"
 #include "swift/Basic/LLVMInitialize.h"
 #include "swift/DependencyScan/DependencyScanImpl.h"
 #include "swift/DependencyScan/DependencyScanningTool.h"
@@ -131,9 +130,6 @@ void swiftscan_scanner_cache_reset(swiftscan_scanner_t scanner) {
 
 swiftscan_scanner_t swiftscan_scanner_create(void) {
   INITIALIZE_LLVM();
-  // We must initialize the swift modules responsible for parsing functionality,
-  // such as parsing regex.
-  initializeSwiftParseModules();
   return wrap(new DependencyScanningTool());
 }