[Driver][Darwin] Use Host Triple to infer target os version

Summary:
When clang required to infer target os version from --target option and
the os version is not specified in targets, check the host triple. If the
host and target are both macOS, use host triple to infer target os
version.

rdar://problem/41651999

Reviewers: arphaman, dexonsmith

Reviewed By: arphaman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D48849

llvm-svn: 336168

1 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/Driver/ToolChains/Darwin.cpp b/clang/lib/Driver/ToolChains/Darwin.cpp
index d0c633b1207..11f77096ae9 100644
--- a/clang/lib/Driver/ToolChains/Darwin.cpp
+++ b/clang/lib/Driver/ToolChains/Darwin.cpp
@@ -1472,10 +1472,16 @@ Optional<DarwinPlatform> inferDeploymentTargetFromSDK(DerivedArgList &Args) {
 std::string getOSVersion(llvm::Triple::OSType OS, const llvm::Triple &Triple,
                          const Driver &TheDriver) {
   unsigned Major, Minor, Micro;
+  llvm::Triple SystemTriple(llvm::sys::getProcessTriple());
   switch (OS) {
   case llvm::Triple::Darwin:
   case llvm::Triple::MacOSX:
-    if (!Triple.getMacOSXVersion(Major, Minor, Micro))
+    // If there is no version specified on triple, and both host and target are
+    // macos, use the host triple to infer OS version.
+    if (Triple.isMacOSX() && SystemTriple.isMacOSX() &&
+        !Triple.getOSMajorVersion())
+      SystemTriple.getMacOSXVersion(Major, Minor, Micro);
+    else if (!Triple.getMacOSXVersion(Major, Minor, Micro))
       TheDriver.Diag(diag::err_drv_invalid_darwin_version)
           << Triple.getOSName();
     break;