[stage1][PATCH] Provide warning for missing jobserver.

[Martin Liška]

Hi.

I'm suggesting to provide a warning when one uses -flto=jobserver
but we can't detect job server for some reason.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Ready to be installed in next stage1?
Thanks,
Martin

gcc/ChangeLog:

2020-03-26  Martin Liska  <mli...@suse.cz>

        PR driver/94330
        * lto-wrapper.c (run_gcc): When using -flto=jobserver,
        report warning when the jobserver is not detected.
---
 gcc/lto-wrapper.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)



diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
index 46a88b233f6..6263c164888 100644
--- a/gcc/lto-wrapper.c
+++ b/gcc/lto-wrapper.c
@@ -1473,10 +1473,16 @@ run_gcc (unsigned argc, char *argv[])
       auto_parallel = 0;
       parallel = 0;
     }
-  else if (!jobserver && jobserver_active_p ())
+  else
     {
-      parallel = 1;
-      jobserver = 1;
+      bool active_jobserver = jobserver_active_p ();
+      if (jobserver && !active_jobserver)
+	warning (0, "jobserver is not available.");
+      else if (!jobserver && active_jobserver)
+	{
+	  parallel = 1;
+	  jobserver = 1;
+	}
     }
 
   if (linker_output)