[SR-237] Move stdlib deployment targets to Python

Migrate the logic that determines which platforms to build the stdlib
for to Python. This is applies both as an effort to migrate more of the
build script to Python (https://bugs.swift.org/browse/SR-237), but also
as a means of splitting up the work necessary to cross-compile the Swift
stdlib from OS X to Linux.

Author: modocache

utils/build-script

@@ -306,6 +306,12 @@ details of the setups of other systems or automated environments.""")
              "target. The built LLVM and Clang will be used to compile Swift "
              "for the cross-compilation targets.",
         default=swift_build_support.targets.host_target())
+    targets_group.add_argument(
+        "--stdlib-deployment-targets",
+        help="list of targets to compile or cross-compile the Swift standard "
+             "library for. %(default)s by default.",
+        nargs="*",
+        default=swift_build_support.targets.stdlib_deployment_targets())
 
     projects_group = parser.add_argument_group(
         title="Options to select projects")
@@ -756,6 +762,7 @@ the number of parallel build jobs to use""",
         '--darwin-xcrun-toolchain',
         '--cmake',
         '--host-target',
+        '--stdlib-deployment-targets',
         '--skip-build',
         '--show-sdks',
         '--install-prefix',
@@ -772,7 +779,7 @@ the number of parallel build jobs to use""",
         '--skip-test-watchos-host',
     ]))
 
-    if args.host_target is None:
+    if args.host_target is None or args.stdlib_deployment_targets is None:
         print_with_argv0("Unknown operating system.")
         return 1
 
@@ -1110,6 +1117,8 @@ the number of parallel build jobs to use""",
         "--build-dir", build_dir,
         "--install-prefix", os.path.abspath(args.install_prefix),
         "--host-target", args.host_target,
+        "--stdlib-deployment-targets",
+        " ".join(args.stdlib_deployment_targets),
         "--host-cc", host_clang.cc,
         "--host-cxx", host_clang.cxx,
         "--darwin-xcrun-toolchain", args.darwin_xcrun_toolchain,

utils/build-script-impl

@@ -186,6 +186,7 @@ KNOWN_SETTINGS=(
     install-libdispatch         ""               "whether to install libdispatch"
     darwin-install-extract-symbols ""            "whether to extract symbols with dsymutil during installations"
     host-target                 ""               "The host target. LLVM, Clang, and Swift will be built for this target. The built LLVM and Clang will be used to compile Swift for the cross-compilation targets. **This argument is required**"
+    stdlib-deployment-targets   ""               "space-separated list of targets to compile or cross-compile the Swift standard library for"
     cross-compile-tools-deployment-targets ""    "space-separated list of targets to cross-compile host Swift tools for"
     skip-merge-lipo-cross-compile-tools ""       "set to skip running merge-lipo after installing cross-compiled host Swift tools"
     darwin-deployment-version-osx     "10.9"     "minimum deployment target version for OS X"
@@ -897,76 +898,6 @@ function is_cross_tools_deployment_target() {
     done
 }
 
-# A list of deployment targets that we compile or cross-compile the
-# Swift standard library for.
-STDLIB_DEPLOYMENT_TARGETS=()
-case "$(uname -s -m)" in
-    Linux\ x86_64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-x86_64"
-            "android-armv7"
-        )
-        ;;
-    Linux\ armv6*)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-armv6"
-        )
-        ;;
-    Linux\ armv7*)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-armv7"
-        )
-        ;;
-    Linux\ aarch64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-aarch64"
-        )
-        ;;
-    Linux\ ppc64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-powerpc64"
-        )
-        ;;
-    Linux\ ppc64le)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "linux-powerpc64le"
-        )
-        ;;
-    Darwin\ x86_64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "macosx-x86_64"
-            "iphonesimulator-i386"
-            "iphonesimulator-x86_64"
-            "appletvsimulator-x86_64"
-            "watchsimulator-i386"
-
-            # Put iOS native targets last so that we test them last (it takes a
-            # long time).
-            "iphoneos-arm64"
-            "iphoneos-armv7"
-            "appletvos-arm64"
-            "watchos-armv7k"
-        )
-        ;;
-
-    FreeBSD\ amd64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "freebsd-x86_64"
-        )
-        ;;
-
-    CYGWIN_NT-10.0\ x86_64)
-        STDLIB_DEPLOYMENT_TARGETS=(
-            "cygwin-x86_64"
-        )
-        ;;
-
-    *)
-        echo "Unknown operating system"
-        exit 1
-        ;;
-esac
-
 #
 # Calculate source directories for each product.
 #
@@ -1058,6 +989,7 @@ SWIFT_STDLIB_TARGETS=()
 SWIFT_BENCHMARK_TARGETS=()
 SWIFT_RUN_BENCHMARK_TARGETS=()
 SWIFT_TEST_TARGETS=()
+STDLIB_DEPLOYMENT_TARGETS=($STDLIB_DEPLOYMENT_TARGETS)
 for deployment_target in "${STDLIB_DEPLOYMENT_TARGETS[@]}"; do
     build_for_this_target=1
     test_this_target=1

utils/swift_build_support/swift_build_support/targets.py

@@ -51,6 +51,57 @@ def host_target():
     return None
 
 
+def stdlib_deployment_targets():
+    """
+    Return deployment targets for the Swift stdlib, based on the host machine.
+    If the host machine is not one of the recognized ones, return None.
+    """
+    system = platform.system()
+    machine = platform.machine()
+
+    if system == 'Linux':
+        if machine == 'x86_64':
+            return [
+                'linux-x86_64',
+                'android-armv7',
+            ]
+        elif machine.startswith('armv6'):
+            # linux-armv6* is canonicalized to 'linux-armv6'
+            return ['linux-armv6']
+        elif machine.startswith('armv7'):
+            # linux-armv7* is canonicalized to 'linux-armv7'
+            return ['linux-armv7']
+        elif machine == 'aarch64':
+            return ['linux-aarch64']
+        elif machine == 'ppc64':
+            return ['linux-ppc64']
+        elif machine == 'ppc64le':
+            return ['linux-ppc64le']
+    elif system == 'Darwin':
+        if machine == 'x86_64':
+            return [
+                'macosx-x86_64',
+                'iphonesimulator-i386',
+                'iphonesimulator-x86_64',
+                'appletvsimulator-x86_64',
+                'watchsimulator-i386',
+                # Put iOS native targets last so that we test them last
+                # (it takes a long time).
+                'iphoneos-arm64',
+                'iphoneos-armv7',
+                'appletvos-arm64',
+                'watchos-armv7k',
+            ]
+    elif system == 'FreeBSD':
+        if machine == 'amd64':
+            return ['freebsd-x86_64']
+    elif system == 'CYGWIN_NT-10.0':
+        if machine == 'x86_64':
+            return ['cygwin-x86_64']
+
+    return None
+
+
 def install_prefix():
     """
     Returns the default path at which built Swift products (like bin, lib,