[PATCH] lto/114655 - -flto=4 at link time doesn't override -flto=auto at compile time

[Richard Biener]

The following adjusts -flto option processing in lto-wrapper to have
link-time -flto override any compile time setting.

LTO-boostrapped on x86_64-unknown-linux-gnu, testing in progress.

OK for trunk and branches?  GCC 11 seems to be unaffected by this.

Thanks,
Richard.

        PR lto/114655
        * lto-wrapper.cc (merge_flto_options): Add force argument.
        (merge_and_complain): Do not force here.
        (run_gcc): But here to make the link-time -flto option override
        any compile-time one.
---
 gcc/lto-wrapper.cc | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/gcc/lto-wrapper.cc b/gcc/lto-wrapper.cc
index 610594cdc2b..02579951569 100644
--- a/gcc/lto-wrapper.cc
+++ b/gcc/lto-wrapper.cc
@@ -218,15 +218,18 @@ find_option (vec<cl_decoded_option> &options, 
cl_decoded_option *option)
   return find_option (options, option->opt_index);
 }
 
-/* Merge -flto FOPTION into vector of DECODED_OPTIONS.  */
+/* Merge -flto FOPTION into vector of DECODED_OPTIONS.  If FORCE is true
+   then FOPTION overrides previous settings.  */
 
 static void
 merge_flto_options (vec<cl_decoded_option> &decoded_options,
-                   cl_decoded_option *foption)
+                   cl_decoded_option *foption, bool force)
 {
   int existing_opt = find_option (decoded_options, foption);
   if (existing_opt == -1)
     decoded_options.safe_push (*foption);
+  else if (force)
+    decoded_options[existing_opt].arg = foption->arg;
   else
     {
       if (strcmp (foption->arg, decoded_options[existing_opt].arg) != 0)
@@ -493,7 +496,7 @@ merge_and_complain (vec<cl_decoded_option> &decoded_options,
          break;
 
        case OPT_flto_:
-         merge_flto_options (decoded_options, foption);
+         merge_flto_options (decoded_options, foption, false);
          break;
        }
     }
@@ -1550,8 +1553,8 @@ run_gcc (unsigned argc, char *argv[])
          break;
 
        case OPT_flto_:
-         /* Merge linker -flto= option with what we have in IL files.  */
-         merge_flto_options (fdecoded_options, option);
+         /* Override IL file settings with a linker -flto= option.  */
+         merge_flto_options (fdecoded_options, option, true);
          if (strcmp (option->arg, "jobserver") == 0)
            jobserver_requested = true;
          break;
-- 
2.35.3