Refactor getMinPlatformVersion

The definitions of how version numbers were extracted from target
triples split between the minimum platform version and for determining
the minimum inlining version.

This resulted in inlinable and transparent functions not being imported
correctly on non-Apple platforms where the version number is retained as
part of the target triple.
Specifically, `_checkExpectedExecutor` was found in the module, but
didn't have the appropriate availability version assigned, resulting in
it failing to import and the compiler silently omitting the check in
SILGen when compiling for FreeBSD.

This patch refactors the implementation of `getMinPlatformVersion` into
a separate function that is used in both places so that they cannot get
out of sync again.

Note: This changes how Windows is handled. getMinPlatformVersion
returned an empty version number for Windows, while the availability
implementation returned the OS version number. This makes both
consistently return the OS version number.

include/swift/Basic/LangOptions.h

@@ -22,6 +22,7 @@
 #include "swift/Basic/Feature.h"
 #include "swift/Basic/FunctionBodySkipping.h"
 #include "swift/Basic/LLVM.h"
+#include "swift/Basic/Platform.h"
 #include "swift/Basic/PlaygroundOption.h"
 #include "swift/Basic/Version.h"
 #include "swift/Config.h"
@@ -693,18 +694,7 @@ namespace swift {
     /// This is only implemented on certain OSs. If no target has been
     /// configured, returns v0.0.0.
     llvm::VersionTuple getMinPlatformVersion() const {
-      if (Target.isMacOSX()) {
-        llvm::VersionTuple OSVersion;
-        Target.getMacOSXVersion(OSVersion);
-        return OSVersion;
-      } else if (Target.isiOS()) {
-        return Target.getiOSVersion();
-      } else if (Target.isWatchOS()) {
-        return Target.getOSVersion();
-      } else if (Target.isXROS()) {
-        return Target.getOSVersion();
-      }
-      return llvm::VersionTuple(/*Major=*/0, /*Minor=*/0, /*Subminor=*/0);
+      return getVersionForTriple(Target);
     }
 
     /// Sets an implicit platform condition.

include/swift/Basic/Platform.h

@@ -85,6 +85,9 @@ namespace swift {
   /// returned.
   StringRef getPlatformNameForTriple(const llvm::Triple &triple);
 
+  /// Returns the version tuple for a given target triple
+  llvm::VersionTuple getVersionForTriple(const llvm::Triple &triple);
+
   /// Returns the platform Kind for Darwin triples.
   DarwinPlatformKind getDarwinPlatformKind(const llvm::Triple &triple);
 

lib/Basic/Platform.cpp

@@ -278,6 +278,23 @@ StringRef swift::getPlatformNameForTriple(const llvm::Triple &triple) {
   llvm_unreachable("unsupported OS");
 }
 
+llvm::VersionTuple swift::getVersionForTriple(const llvm::Triple &triple) {
+  if (triple.isMacOSX()) {
+    llvm::VersionTuple OSVersion;
+    triple.getMacOSXVersion(OSVersion);
+    return OSVersion;
+  } else if (triple.isiOS()) {
+    return triple.getiOSVersion();
+  } else if (triple.isWatchOS()) {
+    return triple.getOSVersion();
+  } else if (triple.isXROS()) {
+    return triple.getOSVersion();
+  } else if (triple.isOSWindows()) {
+    return triple.getOSVersion();
+  }
+  return llvm::VersionTuple(/*Major=*/0, /*Minor=*/0, /*Subminor=*/0);
+}
+
 StringRef swift::getMajorArchitectureName(const llvm::Triple &Triple) {
   if (Triple.isOSLinux()) {
     switch (Triple.getSubArch()) {

lib/Frontend/CompilerInvocation.cpp

@@ -56,17 +56,6 @@ swift::CompilerInvocation::CompilerInvocation() {
   setTargetTriple(llvm::sys::getDefaultTargetTriple());
 }
 
-/// Converts a llvm::Triple to a llvm::VersionTuple.
-static llvm::VersionTuple
-getVersionTuple(const llvm::Triple &triple) {
-  if (triple.isMacOSX()) {
-    llvm::VersionTuple OSVersion;
-    triple.getMacOSXVersion(OSVersion);
-    return OSVersion;
-  }
-  return triple.getOSVersion();
-}
-
 void CompilerInvocation::computeRuntimeResourcePathFromExecutablePath(
     StringRef mainExecutablePath, bool shared,
     llvm::SmallVectorImpl<char> &runtimeResourcePath) {
@@ -1623,7 +1612,7 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   // First, set up default minimum inlining target versions.
   auto getDefaultMinimumInliningTargetVersion =
       [&](const llvm::Triple &triple) -> llvm::VersionTuple {
-    const auto targetVersion = getVersionTuple(triple);
+    const auto targetVersion = getVersionForTriple(triple);
 
     // In API modules, default to the version when Swift first became available.
     if (Opts.LibraryLevel == LibraryLevel::API) {