[Bug gcov-profile/58250] New: -fprofile-use causes: "warning: -fprefetch-loop-arrays is not supported with -Os"

[markus at trippelsdorf dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58250

            Bug ID: 58250
           Summary: -fprofile-use causes: "warning: -fprefetch-loop-arrays
                    is not supported with -Os"
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: markus at trippelsdorf dot de

Just noticed this issue during a PGO/LTO Firefox build.
During the -fprofile-use phase I always get the following warning:
 warning: -fprefetch-loop-arrays is not supported with -Os [enabled by default]

This is caused by rev.193135:
   /* Enable sw prefetching at -O3 for CPUS that prefetching is helpful.  */
   if (flag_prefetch_loop_arrays < 0
       && HAVE_prefetch
-      && optimize >= 3
+      && (optimize >= 3 || flag_profile_use)
       && TARGET_SOFTWARE_PREFETCHING_BENEFICIAL)
     flag_prefetch_loop_arrays = 1;


Does the following patch look OK?

diff --git a/gcc/toplev.c b/gcc/toplev.c
index 53f53fd..9955ed4 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1506,7 +1506,7 @@ process_options (void)

   /* This combination of options isn't handled for i386 targets and doesn't
      make much sense anyway, so don't allow it.  */
-  if (flag_prefetch_loop_arrays > 0 && optimize_size)
+  if (flag_prefetch_loop_arrays > 0 && optimize_size && !flag_profile_use)
     {
       warning (0, "-fprefetch-loop-arrays is not supported with -Os");
       flag_prefetch_loop_arrays = 0;