[clang][Driver] Update/cleanup LTO logic to ensure that the last lto argument is honored

- Make flto an alias of flto=full.
- Make foffload-lto an alias of foffload-lto=full.
- Make flto_EQ_jobserver, flto_EQ_auto aliases of flto=full,
  since they are being treated as full lto right now.
- Clean up the code for parseLTOMode and setLTOMode.
- Replace uses of OPT_flto with OPT_flto_EQ since they alias now.

Differential Revision: https://reviews.llvm.org/D108881

Change-Id: I5d867db83a680434fba5c8d85c9a83135d3b81ee

1 files changed, 3 insertions, 2 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 014595c..c23740fd 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1419,7 +1419,7 @@ void CompilerInvocation::GenerateCodeGenArgs(
   }
 
   if (Opts.PrepareForLTO && !Opts.PrepareForThinLTO)
-    GenerateArg(Args, OPT_flto, SA);
+    GenerateArg(Args, OPT_flto_EQ, "full", SA);
 
   if (Opts.PrepareForThinLTO)
     GenerateArg(Args, OPT_flto_EQ, "thin", SA);
@@ -1706,9 +1706,10 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
     }
   }
 
-  Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
+  Opts.PrepareForLTO = false;
   Opts.PrepareForThinLTO = false;
   if (Arg *A = Args.getLastArg(OPT_flto_EQ)) {
+    Opts.PrepareForLTO = true;
     StringRef S = A->getValue();
     if (S == "thin")
       Opts.PrepareForThinLTO = true;