diff --git a/test/Interop/Cxx/class/debug-info-irgen.swift b/test/Interop/Cxx/class/debug-info-irgen.swift
index 87bdd867c9886..772c320456d26 100644
--- a/test/Interop/Cxx/class/debug-info-irgen.swift
+++ b/test/Interop/Cxx/class/debug-info-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swiftxx-frontend -I %S/Inputs %s -emit-ir -g | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir -g | %FileCheck %s)
 
 // Validate that we don't crash when trying to deserialize C++ type debug info.
 // Note, however, that the actual debug info is not generated, see SR-13223.
diff --git a/test/Interop/Cxx/class/destructors-correct-abi-irgen.swift b/test/Interop/Cxx/class/destructors-correct-abi-irgen.swift
index 2d355bccb95e7..3d53bff43df4d 100644
--- a/test/Interop/Cxx/class/destructors-correct-abi-irgen.swift
+++ b/test/Interop/Cxx/class/destructors-correct-abi-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %swift -I %S/Inputs -enable-cxx-interop -emit-ir %s | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import Destructors
 
diff --git a/test/Interop/Cxx/class/destructors-non-trivial-implicit-irgen.swift b/test/Interop/Cxx/class/destructors-non-trivial-implicit-irgen.swift
index 39ed1424d41c3..5db68f97f8f18 100644
--- a/test/Interop/Cxx/class/destructors-non-trivial-implicit-irgen.swift
+++ b/test/Interop/Cxx/class/destructors-non-trivial-implicit-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -enable-cxx-interop -I %S/Inputs %s -emit-ir | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import Destructors
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-from-nested-struct-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-from-nested-struct-irgen.swift
index cf37774179d90..2dd5c60fb32a1 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-from-nested-struct-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-from-nested-struct-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import ConstructorCallsFunctionFromNestedStruct
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-irgen.swift
index df594af1a4399..73863ef7befac 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-function-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import ConstructorCallsFunction
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-method-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-method-irgen.swift
index 3cc710101a1ce..c2fd6cff83bbb 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-method-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/constructor-calls-method-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import ConstructorCallsMethod
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/field-init-calls-function-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/field-init-calls-function-irgen.swift
index e806bcf182101..4edaa062aff8a 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/field-init-calls-function-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/field-init-calls-function-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import FieldInitCallsFunction
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/method-calls-function-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/method-calls-function-irgen.swift
index 553349ba21b84..192eb055e9a82 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/method-calls-function-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/method-calls-function-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import MethodCallsFunction
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-from-nested-struct-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-from-nested-struct-irgen.swift
index 391c6050f233e..5a055f7fd4f84 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-from-nested-struct-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-from-nested-struct-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import MethodCallsMethodFromNestedStruct
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-irgen.swift
index 44f8b7c04173b..9613b1b2f932b 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/method-calls-method-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import MethodCallsMethod
 
diff --git a/test/Interop/Cxx/class/inline-function-codegen/static-var-init-calls-function-irgen.swift b/test/Interop/Cxx/class/inline-function-codegen/static-var-init-calls-function-irgen.swift
index 588973b252037..ba63739ae17e4 100644
--- a/test/Interop/Cxx/class/inline-function-codegen/static-var-init-calls-function-irgen.swift
+++ b/test/Interop/Cxx/class/inline-function-codegen/static-var-init-calls-function-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop -validate-tbd-against-ir=none | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir -validate-tbd-against-ir=none | %FileCheck %s)
 
 // TODO: See why -validate-tbd-against-ir=none is needed here (SR-14069)
 
diff --git a/test/Interop/Cxx/class/type-classification-non-trivial-irgen.swift b/test/Interop/Cxx/class/type-classification-non-trivial-irgen.swift
index b7c2af710568c..a7fa5fc6964bf 100644
--- a/test/Interop/Cxx/class/type-classification-non-trivial-irgen.swift
+++ b/test/Interop/Cxx/class/type-classification-non-trivial-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swiftxx-frontend -I %S/Inputs %s -emit-ir | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 // Verify that non-trival/address-only C++ classes are constructed and accessed
 // correctly. Make sure that we correctly IRGen functions that construct
diff --git a/test/Interop/Cxx/extern-var/extern-var-irgen.swift b/test/Interop/Cxx/extern-var/extern-var-irgen.swift
index c23aa07c11edb..0f5d579cf52b1 100644
--- a/test/Interop/Cxx/extern-var/extern-var-irgen.swift
+++ b/test/Interop/Cxx/extern-var/extern-var-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import ExternVar
 
diff --git a/test/Interop/Cxx/namespace/classes-irgen.swift b/test/Interop/Cxx/namespace/classes-irgen.swift
index ecc14ef33cfbb..0a326f2521cfe 100644
--- a/test/Interop/Cxx/namespace/classes-irgen.swift
+++ b/test/Interop/Cxx/namespace/classes-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir -I %S/Inputs -enable-cxx-interop %s | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import Classes
 
diff --git a/test/Interop/Cxx/namespace/free-functions-irgen.swift b/test/Interop/Cxx/namespace/free-functions-irgen.swift
index 1e2da09ed3265..6db3c5a337f83 100644
--- a/test/Interop/Cxx/namespace/free-functions-irgen.swift
+++ b/test/Interop/Cxx/namespace/free-functions-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir -I %S/Inputs -enable-cxx-interop %s | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import FreeFunctions
 
diff --git a/test/Interop/Cxx/namespace/templates-irgen.swift b/test/Interop/Cxx/namespace/templates-irgen.swift
index 9f373ccb0328a..baa7c095dec39 100644
--- a/test/Interop/Cxx/namespace/templates-irgen.swift
+++ b/test/Interop/Cxx/namespace/templates-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir -I %S/Inputs -enable-cxx-interop %s | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import Templates
 
diff --git a/test/Interop/Cxx/static/inline-static-member-var-irgen.swift b/test/Interop/Cxx/static/inline-static-member-var-irgen.swift
index bc65b38e58481..0a3d052a43bed 100644
--- a/test/Interop/Cxx/static/inline-static-member-var-irgen.swift
+++ b/test/Interop/Cxx/static/inline-static-member-var-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir -I %S/Inputs -enable-cxx-interop %s | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import InlineStaticMemberVar
 
diff --git a/test/Interop/Cxx/static/static-member-func-irgen.swift b/test/Interop/Cxx/static/static-member-func-irgen.swift
index 84b1db7afb4f1..b387322c7f21a 100644
--- a/test/Interop/Cxx/static/static-member-func-irgen.swift
+++ b/test/Interop/Cxx/static/static-member-func-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import StaticMemberFunc
 
diff --git a/test/Interop/Cxx/templates/function-template-irgen.swift b/test/Interop/Cxx/templates/function-template-irgen.swift
index fa5bd1c221605..431d8c4cf065a 100644
--- a/test/Interop/Cxx/templates/function-template-irgen.swift
+++ b/test/Interop/Cxx/templates/function-template-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import FunctionTemplates
 
diff --git a/test/Interop/Cxx/templates/linkage-of-swift-symbols-for-imported-types-irgen.swift b/test/Interop/Cxx/templates/linkage-of-swift-symbols-for-imported-types-irgen.swift
index f3a2ae75d69ba..c3dc101443a12 100644
--- a/test/Interop/Cxx/templates/linkage-of-swift-symbols-for-imported-types-irgen.swift
+++ b/test/Interop/Cxx/templates/linkage-of-swift-symbols-for-imported-types-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import LinkageOfSwiftSymbolsForImportedTypes
 
diff --git a/test/Interop/Cxx/templates/mangling-irgen.swift b/test/Interop/Cxx/templates/mangling-irgen.swift
index c55feb8b5dc47..ae579f68937ab 100644
--- a/test/Interop/Cxx/templates/mangling-irgen.swift
+++ b/test/Interop/Cxx/templates/mangling-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 import Mangling
 
diff --git a/test/Interop/Cxx/templates/partially-pre-defined-class-template-irgen.swift b/test/Interop/Cxx/templates/partially-pre-defined-class-template-irgen.swift
index 1dc4ac92f6fee..5ce09b0a42f2b 100644
--- a/test/Interop/Cxx/templates/partially-pre-defined-class-template-irgen.swift
+++ b/test/Interop/Cxx/templates/partially-pre-defined-class-template-irgen.swift
@@ -1,5 +1,7 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
+
 // REQUIRES: rdar67257133
+
 import PartiallyPreDefinedClassTemplate
 
 public func getWrappedMagicInt() -> CInt {
diff --git a/test/Interop/Cxx/value-witness-table/custom-destructors-non-virtual-irgen.swift b/test/Interop/Cxx/value-witness-table/custom-destructors-non-virtual-irgen.swift
index 19c4fef206c9f..588fec97e5193 100644
--- a/test/Interop/Cxx/value-witness-table/custom-destructors-non-virtual-irgen.swift
+++ b/test/Interop/Cxx/value-witness-table/custom-destructors-non-virtual-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend -enable-cxx-interop -I %S/Inputs %s -emit-ir | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 // This tests output needs to be updated for arm64.
 // XFAIL: CPU=arm64e
diff --git a/test/Interop/Cxx/value-witness-table/witness-layout-opts-irgen.swift b/test/Interop/Cxx/value-witness-table/witness-layout-opts-irgen.swift
index 42bea66b5b03d..2ef68551621dd 100644
--- a/test/Interop/Cxx/value-witness-table/witness-layout-opts-irgen.swift
+++ b/test/Interop/Cxx/value-witness-table/witness-layout-opts-irgen.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-ir %s -I %S/Inputs -enable-cxx-interop | %FileCheck %s
+// RUN: %cxx-all-targets(-I %S/Inputs %s -emit-ir | %FileCheck %s)
 
 // This test checks that the compiler uses well-known witness tables for types
 // that have the appropriate size/shape (for example, { i8 x 4 } -> i32).
diff --git a/test/lit.cfg b/test/lit.cfg
index b311cd0307649..4c2458dac7c58 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -2203,6 +2203,16 @@ if platform.system() != 'Darwin' or swift_test_mode == 'optimize_none_with_impli
 #
 
 config.substitutions.append(('%target-clangxx', '%s -std=c++11' % config.target_clang))
+config.substitutions.append(('%cxx-all-targets\(([^)]+)\)',
+                             SubstituteCaptures(r"%s -disable-legacy-type-info -enable-cxx-interop -I %s/uswift-macos-arm64/swift -target arm64-apple-macosx10.9 \1 && "
+                                                r"%s -disable-legacy-type-info -enable-cxx-interop -I %s/uswift-macos-x86_64/swift -target x86_64-apple-macosx10.9 \1 && "
+                                                r"%s -enable-cxx-interop -I %s/uswift-linux-armv7/swift -target armv7-unknown-linux-androideabi \1 &&"
+                                                r"%s -enable-cxx-interop -I %s/uswift-windows-x86_64/swift -target x86_64-unknown-windows-msvc \1 "
+                                                % (config.swift_frontend, shell_quote(os.path.realpath(swift_obj_root).replace("\\", "/")),
+                                                   config.swift_frontend, shell_quote(os.path.realpath(swift_obj_root).replace("\\", "/")),
+                                                   config.swift_frontend, shell_quote(os.path.realpath(swift_obj_root).replace("\\", "/")),
+                                                   config.swift_frontend, shell_quote(os.path.realpath(swift_obj_root).replace("\\", "/"))) )
+                           ))
 config.substitutions.append(('%target-swiftxx-frontend', '%s -enable-cxx-interop' % config.target_swift_frontend))
 
 config.substitutions.append(('%target-runtime', config.target_runtime))
diff --git a/utils/build-script-impl b/utils/build-script-impl
index 355f1a086d86d..dd14358e3bbea 100755
--- a/utils/build-script-impl
+++ b/utils/build-script-impl
@@ -1245,6 +1245,7 @@ NINJA_SOURCE_DIR="${WORKSPACE}/ninja"
 SWIFT_SOURCE_DIR="${WORKSPACE}/swift"
 LLVM_SOURCE_DIR="${WORKSPACE}/llvm-project/llvm"
 CMARK_SOURCE_DIR="${WORKSPACE}/cmark"
+USWIFT_SOURCE_DIR="${WORKSPACE}/uswift"
 LLDB_SOURCE_DIR="${WORKSPACE}/llvm-project/lldb"
 LLBUILD_SOURCE_DIR="${WORKSPACE}/llbuild"
 STRESSTEST_PACKAGE_DIR="${WORKSPACE}/swift-stress-tester"
@@ -1266,6 +1267,7 @@ PRODUCTS=(llvm)
 [[ "${SKIP_BUILD_LIBCXX}" ]] || PRODUCTS+=(libcxx)
 [[ "${SKIP_BUILD_LIBICU}" ]] || PRODUCTS+=(libicu)
 [[ "${SKIP_BUILD_SWIFT}" ]] || PRODUCTS+=(swift)
+PRODUCTS+=(uswift)
 [[ "${SKIP_BUILD_LLDB}" ]] || PRODUCTS+=(lldb)
 [[ "${SKIP_BUILD_LIBDISPATCH}" ]] || PRODUCTS+=(libdispatch)
 [[ "${SKIP_BUILD_STATIC_LIBDISPATCH}" ]] || PRODUCTS+=(libdispatch_static)
@@ -1356,6 +1358,8 @@ function build_directory_bin() {
                 ;;
             libicu)
                 ;;
+            uswift)
+                ;;
             *)
                 echo "error: unknown product: ${product}"
                 exit 1
@@ -1759,6 +1763,91 @@ for host in "${ALL_HOSTS[@]}"; do
                 build_targets=(all)
                 ;;
 
+            uswift)
+                uswift_targets=(
+                    "macos-arm64" "arm64-apple-macosx10.9"
+                    "macos-x86_64" "x86_64-apple-macosx10.9"
+                    "linux-armv7" "armv7-unknown-linux-androideabi"
+                    "windows-x86_64" "x86_64-unknown-windows-msvc"
+                )
+                uswift_targets_length=${#uswift_targets[@]}
+
+                cmake_options=(
+                    "${cmake_options[@]}"
+                    -D BUILD_SHARED_LIBS=NO
+                    -D CMAKE_Swift_COMPILER_WORKS=YES
+                    -D CMAKE_BUILD_TYPE=Release
+                    -D CMAKE_Swift_COMPILER=$(build_directory ${host} swift)/bin/swiftc
+                )
+
+                # Build uswift for each target.
+                for (( i=1; i<${uswift_targets_length}+1; i+=2 ));
+                do
+                    uswift_target_name=${uswift_targets[$i-1]}
+                    uswift_target=${uswift_targets[$i]}
+                    all_cmake_options=(
+                        "${cmake_options[@]}"
+                        -D CMAKE_Swift_COMPILER_TARGET=${uswift_target}
+                    )
+
+                    if [[ "$uswift_target_name" == "windows-x86_64" ]] ; then
+                        all_cmake_options=(
+                            "${all_cmake_options[@]}"
+                            -D CMAKE_Swift_FLAGS="-use-ld=$(build_directory ${LOCAL_HOST} llvm)/bin/lld-link"
+                        )
+                    else
+                        all_cmake_options=(
+                            "${all_cmake_options[@]}"
+                            -D CMAKE_Swift_FLAGS="-Xfrontend -disable-legacy-type-info"
+                        )
+                    fi
+
+                    build_dir=$(build_directory ${uswift_target_name} ${product})
+
+                    generator_output_path=""
+                    if [[ "${CMAKE_GENERATOR}" == "Ninja" ]] ; then
+                        generator_output_path="${build_dir}/build.ninja"
+                    fi
+
+                    # Configure if necessary.
+                    cmake_cache_path="${build_dir}/CMakeCache.txt"
+                    if [[  "${RECONFIGURE}" || ! -f "${cmake_cache_path}" || \
+                                ( ! -z "${generator_output_path}" && ! -f "${generator_output_path}" ) ]] ; then
+                        call mkdir -p "${build_dir}"
+
+                        # Use `cmake-file-api` in case it is available.
+                        call mkdir -p "${build_dir}/.cmake/api/v1/query"
+                        call touch "${build_dir}/.cmake/api/v1/query/codemodel-v2" "${build_dir}/.cmake/api/v1/query/cache-v2"
+
+                        if [[ -n "${DISTCC}" ]]; then
+                            EXTRA_DISTCC_OPTIONS=("DISTCC_HOSTS=localhost,lzo,cpp")
+                        fi
+                        with_pushd "${build_dir}" \
+                            call env "${EXTRA_DISTCC_OPTIONS[@]}" "${CMAKE}" "${all_cmake_options[@]}" "${EXTRA_CMAKE_OPTIONS[@]}" "${source_dir}"
+                    fi
+
+                    # Note: unconditionally build uswift because it is required for running some tests.
+                    if [[ "${CMAKE_GENERATOR}" == "Xcode" ]] ; then
+                        # Xcode generator uses "ALL_BUILD" instead of "all".
+                        # Also, xcodebuild uses -target instead of bare names.
+                        build_targets=("${build_targets[@]/all/ALL_BUILD}")
+                        build_targets=("${build_targets[@]/#/${BUILD_TARGET_FLAG} }")
+
+                        # Xcode can't restart itself if it turns out we need to reconfigure.
+                        # Do an advance build to handle that.
+                        call "${CMAKE_BUILD[@]}" "${build_dir}" $(cmake_config_opt ${product})
+                    fi
+
+                    call "${CMAKE_BUILD[@]}" "${build_dir}" $(cmake_config_opt ${product}) -- "${BUILD_ARGS[@]}" ${build_targets[@]}
+
+                    # Copy over the uswift build.
+                    cp -a $(build_directory ${uswift_target_name} uswift) $(build_directory ${host} swift)
+                done
+
+                # We've already run cmake/build so we can just break out here.
+                continue
+                ;;
+
             llvm)
                 if [[ -n "${LLVM_NINJA_TARGETS_FOR_CROSS_COMPILE_HOSTS}" && $(is_cross_tools_host ${host}) ]] ; then
                     build_targets=("${LLVM_NINJA_TARGETS_FOR_CROSS_COMPILE_HOSTS[@]}")
@@ -1817,7 +1906,7 @@ for host in "${ALL_HOSTS[@]}"; do
                     "${llvm_cmake_options[@]}"
                 )
 
-                llvm_enable_projects=("clang")
+                llvm_enable_projects=("clang" "lld")
 
                 if [[ ! "${SKIP_BUILD_COMPILER_RT}" && ! $(is_cross_tools_host ${host}) ]]; then
                     llvm_enable_projects+=("compiler-rt")
@@ -1827,18 +1916,6 @@ for host in "${ALL_HOSTS[@]}"; do
                     llvm_enable_projects+=("clang-tools-extra")
                 fi
 
-                # On non-Darwin platforms, build lld so we can always have a
-                # linker that is compatible with the swift we are using to
-                # compile the stdlib.
-                #
-                # This makes it easier to build target stdlibs on systems that
-                # have old toolchains without more modern linker features.
-                if [[ "$(uname -s)" != "Darwin" ]] ; then
-                    if [[ ! "${SKIP_BUILD_LLD}" ]]; then
-                        llvm_enable_projects+=("lld")
-                    fi
-                fi
-
                 cmake_options+=(
                     -DLLVM_ENABLE_PROJECTS="$(join ";" ${llvm_enable_projects[@]})"
                 )
@@ -1898,7 +1975,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 ;;
 
             swift)
-
                 if [[ "${ANDROID_API_LEVEL}" ]]; then
                     cmake_options=(
                         "${cmake_options[@]}"
@@ -2808,6 +2884,9 @@ for host in "${ALL_HOSTS[@]}"; do
             libcxx)
                 continue # We don't test libc++
                 ;;
+            uswift)
+                continue # We don't test uswift
+                ;;
             swift)
                 executable_target=
                 results_targets=
@@ -3159,6 +3238,9 @@ for host in "${ALL_HOSTS[@]}"; do
                 fi
                 INSTALL_TARGETS=install-swift-components
                 ;;
+            uswift)
+                continue
+                ;;
             llbuild)
                 if [[ -z "${INSTALL_LLBUILD}" ]] ; then
                     continue
diff --git a/utils/build_swift/build_swift/driver_arguments.py b/utils/build_swift/build_swift/driver_arguments.py
index 738042364c5a9..d2565074e04b1 100644
--- a/utils/build_swift/build_swift/driver_arguments.py
+++ b/utils/build_swift/build_swift/driver_arguments.py
@@ -346,7 +346,7 @@ def create_argument_parser():
            help='enable code coverage analysis in Swift (false, not-merged, '
                 'merged).')
 
-    option('--swift-disable-dead-stripping', toggle_true, 
+    option('--swift-disable-dead-stripping', toggle_true,
            help="Turn off Darwin-specific dead stripping for Swift host tools")
 
     option('--build-subdir', store,
@@ -1252,6 +1252,8 @@ def create_argument_parser():
            help='skip building llvm')
     option('--skip-build-swift', toggle_false('build_swift'),
            help='skip building swift')
+    option('--skip-build-uswift', toggle_false('build_uswift'),
+           help='skip building uswift')
 
     # We need to list --skip-test-swift explicitly because otherwise argparse
     # will auto-expand arguments like --skip-test-swift to the only known
diff --git a/utils/build_swift/tests/expected_options.py b/utils/build_swift/tests/expected_options.py
index 9984cf0c439f3..9d4415fd69f76 100644
--- a/utils/build_swift/tests/expected_options.py
+++ b/utils/build_swift/tests/expected_options.py
@@ -58,6 +58,7 @@
     'build_foundation': False,
     'build_cmark': True,
     'build_swift': True,
+    'build_uswift': True,
     'build_llvm': True,
     'build_freebsd': True,
     'build_ios': True,
@@ -597,6 +598,7 @@ class BuildScriptImplOption(_BaseOption):
     DisableOption('--skip-build-cmark', dest='build_cmark'),
     DisableOption('--skip-build-llvm', dest='build_llvm'),
     DisableOption('--skip-build-swift', dest='build_swift'),
+    DisableOption('--skip-build-uswift', dest='build_uswift'),
 
     DisableOption('--skip-build-android', dest='build_android'),
     DisableOption('--skip-build-benchmarks', dest='build_benchmarks'),
diff --git a/utils/swift_build_support/swift_build_support/build_script_invocation.py b/utils/swift_build_support/swift_build_support/build_script_invocation.py
index 3ae3002f5d906..9390eda48060a 100644
--- a/utils/swift_build_support/swift_build_support/build_script_invocation.py
+++ b/utils/swift_build_support/swift_build_support/build_script_invocation.py
@@ -250,6 +250,7 @@ def convert_to_impl_arguments(self):
             (args.build_cmark, "cmark"),
             (args.build_llvm, "llvm"),
             (args.build_swift, "swift"),
+            (args.build_uswift, "uswift"),
             (args.build_foundation, "foundation"),
             (args.build_xctest, "xctest"),
             (args.build_lldb, "lldb"),
@@ -562,6 +563,8 @@ def compute_product_pipelines(self):
                                  is_enabled=self.args.build_libicu)
         builder.add_impl_product(products.Swift,
                                  is_enabled=self.args.build_swift)
+        builder.add_impl_product(products.USwift,
+                                 is_enabled=self.args.build_uswift)
         builder.add_impl_product(products.LLDB,
                                  is_enabled=self.args.build_lldb)
 
diff --git a/utils/swift_build_support/swift_build_support/products/__init__.py b/utils/swift_build_support/swift_build_support/products/__init__.py
index 7cdd61fb504fb..8de2336cc8b7d 100644
--- a/utils/swift_build_support/swift_build_support/products/__init__.py
+++ b/utils/swift_build_support/swift_build_support/products/__init__.py
@@ -14,6 +14,7 @@
 from .benchmarks import Benchmarks
 from .cmark import CMark
 from .earlyswiftdriver import EarlySwiftDriver
+from .uswift import USwift
 from .foundation import Foundation
 from .indexstoredb import IndexStoreDB
 from .libcxx import LibCXX
@@ -40,6 +41,7 @@
 
 __all__ = [
     'BackDeployConcurrency',
+    'USwift',
     'CMark',
     'Ninja',
     'Foundation',
diff --git a/utils/swift_build_support/swift_build_support/products/uswift.py b/utils/swift_build_support/swift_build_support/products/uswift.py
new file mode 100644
index 0000000000000..9f37f8696cf3a
--- /dev/null
+++ b/utils/swift_build_support/swift_build_support/products/uswift.py
@@ -0,0 +1,28 @@
+# swift_build_support/products/cmark.py -------------------------*- python -*-
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2017 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
+#
+# ----------------------------------------------------------------------------
+
+from . import product
+
+
+class USwift(product.Product):
+    @classmethod
+    def is_build_script_impl_product(cls):
+        """is_build_script_impl_product -> bool
+
+        Whether this product is produced by build-script-impl.
+        """
+        return True
+
+    # This is the root of the build-graph, so it doesn't have any dependencies.
+    @classmethod
+    def get_dependencies(cls):
+        return []
diff --git a/utils/update_checkout/update-checkout-config.json b/utils/update_checkout/update-checkout-config.json
index 5b3e3b3be5c69..d88d27b4b98cd 100644
--- a/utils/update_checkout/update-checkout-config.json
+++ b/utils/update_checkout/update-checkout-config.json
@@ -11,7 +11,7 @@
         "swift-argument-parser": {
             "remote": { "id": "apple/swift-argument-parser" } },
         "swift-atomics": {
-            "remote": { "id": "apple/swift-atomics" } },       
+            "remote": { "id": "apple/swift-atomics" } },
         "swift-collections": {
             "remote": { "id": "apple/swift-collections" } },
         "swift-crypto": {
@@ -19,7 +19,7 @@
         "swift-driver": {
             "remote": { "id": "apple/swift-driver" } },
         "swift-numerics": {
-            "remote": { "id": "apple/swift-numerics" } },        
+            "remote": { "id": "apple/swift-numerics" } },
         "swift-tools-support-core": {
             "remote": { "id": "apple/swift-tools-support-core" } },
         "swiftpm": {
@@ -80,7 +80,9 @@
         "swift-experimental-string-processing": {
             "remote": { "id": "apple/swift-experimental-string-processing" } },
         "llvm-project": {
-            "remote": { "id": "apple/llvm-project" } }
+            "remote": { "id": "apple/llvm-project" } },
+        "uswift": {
+          "remote": { "id": "compnerd/uswift" } }
     },
     "default-branch-scheme": "main",
     "branch-schemes": {
@@ -123,7 +125,8 @@
                 "swift-cmark-gfm": "gfm",
                 "swift-nio": "2.31.2",
                 "swift-nio-ssl": "2.15.0",
-                "swift-experimental-string-processing": "dev/6"
+                "swift-experimental-string-processing": "dev/6",
+                "uswift": "main"
             }
         },
         "rebranch": {
@@ -198,7 +201,8 @@
                 "swift-markdown": "release/5.6",
                 "swift-cmark-gfm": "release/5.6-gfm",
                 "swift-nio": "2.31.2",
-                "swift-nio-ssl": "2.15.0"
+                "swift-nio-ssl": "2.15.0",
+                "uswift": "main"
             }
         },
        "release/5.5": {
@@ -288,12 +292,12 @@
                 "swiftpm": "main",
                 "swift-argument-parser": "1.0.3",
                 "swift-atomics": "1.0.2",
-                "swift-collections": "1.0.1",                
-                "swift-crypto": "1.1.5",                
+                "swift-collections": "1.0.1",
+                "swift-crypto": "1.1.5",
                 "swift-driver": "main",
                 "swift-numerics": "1.0.1",
                 "swift-syntax": "main",
-                "swift-system": "1.1.1",                
+                "swift-system": "1.1.1",
                 "swift-stress-tester": "main",
                 "swift-corelibs-xctest": "main",
                 "swift-corelibs-foundation": "main",
@@ -308,7 +312,8 @@
                 "sourcekit-lsp": "main",
                 "swift-format": "main",
                 "swift-installer-scripts": "main",
-                "swift-experimental-string-processing": "dev/6"
+                "swift-experimental-string-processing": "dev/6",
+                "uswift": "main"
             }
         },
         "release/5.4": {