Fix parsing of branch target protection options on arm64 to enable BTI and PAC again by default on OpenBSD.

ok robert@

Author: kettenis

clang/lib/Driver/ToolChains/Clang.cpp

@@ -1566,15 +1566,21 @@ void AddUnalignedAccessWarning(ArgStringList &CmdArgs) {
 
 static void CollectARMPACBTIOptions(const ToolChain &TC, const ArgList &Args,
                                     ArgStringList &CmdArgs, bool isAArch64) {
+  const llvm::Triple &Triple = TC.getEffectiveTriple();
   const Arg *A = isAArch64
                      ? Args.getLastArg(options::OPT_msign_return_address_EQ,
                                        options::OPT_mbranch_protection_EQ)
                      : Args.getLastArg(options::OPT_mbranch_protection_EQ);
-  if (!A)
+  if (!A) {
+    if (Triple.isOSOpenBSD()) {
+      CmdArgs.push_back("-msign-return-address=non-leaf");
+      CmdArgs.push_back("-msign-return-address-key=a_key");
+      CmdArgs.push_back("-mbranch-target-enforce");
+    }
     return;
+  }
 
   const Driver &D = TC.getDriver();
-  const llvm::Triple &Triple = TC.getEffectiveTriple();
   if (!(isAArch64 || (Triple.isArmT32() && Triple.isArmMClass())))
     D.Diag(diag::warn_incompatible_branch_protection_option)
         << Triple.getArchName();
@@ -1613,13 +1619,6 @@ static void CollectARMPACBTIOptions(const ToolChain &TC, const ArgList &Args,
         Args.MakeArgString(Twine("-msign-return-address-key=") + Key));
   if (IndirectBranches)
     CmdArgs.push_back("-mbranch-target-enforce");
-  else {
-    if (Triple.isOSOpenBSD()) {
-      CmdArgs.push_back("-msign-return-address=non-leaf");
-      CmdArgs.push_back("-msign-return-address-key=a_key");
-      CmdArgs.push_back("-mbranch-target-enforce");
-    }
-  }
 }
 
 void Clang::AddARMTargetArgs(const llvm::Triple &Triple, const ArgList &Args,