On PowerPC, Secure-PLT by default for FreeBSD 13 and higher

[dim]

Summary

In https://svnweb.freebsd.org/changeset/base/349351, FreeBSD 13 and
higher transitioned to Secure-PLT for PowerPC. This part contains the
changes in llvm's PPC subtarget.

[jhibbits]

Thanks for pushing these through. They've been sitting in my private repo for too long now out of laziness.

llvm/trunk/lib/Target/PowerPC/PPCSubtarget.cpp

void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
   // support it, ignore.
   if (IsPPC64 && has64BitSupport())
     Use64BitRegs = true;
 
   // Set up darwin-specific properties.
   if (isDarwin())
     HasLazyResolverStubs = true;
 
-  if (TargetTriple.isOSNetBSD() || TargetTriple.isOSOpenBSD() ||
+  if ((TargetTriple.isOSFreeBSD() && TargetTriple.getOSMajorVersion() >= 13) ||
+      TargetTriple.isOSNetBSD() || TargetTriple.isOSOpenBSD() ||
       TargetTriple.isMusl())
     SecurePlt = true;
 
   if (HasSPE && IsPPC64)
     report_fatal_error( "SPE is only supported for 32-bit targets.\n", false);
   if (HasSPE && (HasAltivec || HasQPX || HasVSX || HasFPU))
     report_fatal_error(
         "SPE and traditional floating point cannot both be enabled.\n", false);