[NFCi] Switch ordering of ParseLangArgs and ParseCodeGenArgs.

[plotfi]

Summary

After speaking with @ab and @rjmccall on https://reviews.llvm.org/D72841#2027740 and https://github.com/apple/llvm-project/pull/1202.

it sounds like code-gen option parsing should depend on language-option parsing, not the other way around. Apple Clang llvm-project master does this in the right order but upstream llvm.org does it in the opposite order.

This patch changes the order to the way apple-master does it, which we think is the correct order. At the moment D72841 causes some bot failures on apple-master (only on tests added in D72841). I think D72841 should be reverted, and then reapplied after _this_ patch is landed.

[rjmccall]

I don't think the reversion is necessary; it's being fixed to remove the dependency. This is a good change, though.

[plotfi]

In D79730#2030037, @rjmccall wrote:

I don't think the reversion is necessary; it's being fixed to remove the dependency. This is a good change, though.

Should I still try to land this diff so that it matches the behavior on Apple master? Might catch any future dependency issues.

[rjmccall]

I think it makes sense; if nothing else, we're trying to upstream all that work.

[plotfi]

In D79730#2030530, @rjmccall wrote:

I think it makes sense; if nothing else, we're trying to upstream all that work.

@rjmccall Should I still try to land this or should this stuff get pushed in as part of the apple/master upstreaming effort @dexonsmith mentioned on the llvm list? I can abandon this diff if thats the plan.

[rjmccall]

Either way, I think.

[plotfi]

Update for harbormaster.

clang/lib/Frontend/CompilerInvocation.cpp

   InputKind DashX = ParseFrontendArgs(Res.getFrontendOpts(), Args, Diags,
                                       LangOpts.IsHeaderFile);
   ParseTargetArgs(Res.getTargetOpts(), Args, Diags);
-  Success &= ParseCodeGenArgs(Res.getCodeGenOpts(), Args, DashX, Diags,
-                              Res.getTargetOpts(), Res.getFrontendOpts());
   ParseHeaderSearchArgs(Res.getHeaderSearchOpts(), Args,
                         Res.getFileSystemOpts().WorkingDir);
   llvm::Triple T(Res.getTargetOpts().Triple);

   LangOpts.FunctionAlignment =
       getLastArgIntValue(Args, OPT_function_alignment, 0, Diags);
 
+  Success &= ParseCodeGenArgs(Res.getCodeGenOpts(), Args, DashX, Diags,
+                              Res.getTargetOpts(), Res.getFrontendOpts());
+
   if (LangOpts.CUDA) {
     // During CUDA device-side compilation, the aux triple is the
     // triple used for host compilation.