Factor out jobserver_active_p.

gcc/ChangeLog:

	* gcc.c (driver::detect_jobserver): Remove and move to
	jobserver.h.
	* lto-wrapper.c (jobserver_active_p): Likewise.
	(run_gcc): Likewise.
	* opts-jobserver.h: New file.
	* opts-common.c (jobserver_info::jobserver_info): New function.

(cherry picked from commit 1270ccda70ca09f7d4fe76b5156dca8992bd77a6)

4 files changed, 114 insertions, 61 deletions

diff --git a/gcc/gcc.c b/gcc/gcc.c
index 6d0f857..ed7099c 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -27,6 +27,7 @@ CC recognizes how to compile each input file by suffixes in the file names.
 Once it knows which kind of compilation to perform, the procedure for
 compilation is specified by a string called a "spec".  */
 
+#define INCLUDE_STRING
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
@@ -43,6 +44,7 @@ compilation is specified by a string called a "spec".  */
 #include "opts.h"
 #include "filenames.h"
 #include "spellcheck.h"
+#include "opts-jobserver.h"
 
 
 
@@ -8399,38 +8401,9 @@ driver::final_actions () const
 void
 driver::detect_jobserver () const
 {
-  /* Detect jobserver and drop it if it's not working.  */
-  const char *makeflags = env.get ("MAKEFLAGS");
-  if (makeflags != NULL)
-    {
-      const char *needle = "--jobserver-auth=";
-      const char *n = strstr (makeflags, needle);
-      if (n != NULL)
-	{
-	  int rfd = -1;
-	  int wfd = -1;
-
-	  bool jobserver
-	    = (sscanf (n + strlen (needle), "%d,%d", &rfd, &wfd) == 2
-	       && rfd > 0
-	       && wfd > 0
-	       && is_valid_fd (rfd)
-	       && is_valid_fd (wfd));
-
-	  /* Drop the jobserver if it's not working now.  */
-	  if (!jobserver)
-	    {
-	      unsigned offset = n - makeflags;
-	      char *dup = xstrdup (makeflags);
-	      dup[offset] = '\0';
-
-	      const char *space = strchr (makeflags + offset, ' ');
-	      if (space != NULL)
-		strcpy (dup + offset, space);
-	      xputenv (concat ("MAKEFLAGS=", dup, NULL));
-	    }
-	}
-    }
+  jobserver_info jinfo;
+  if (!jinfo.is_active && !jinfo.skipped_makeflags.empty ())
+    xputenv (jinfo.skipped_makeflags.c_str ());
 }
 
 /* Determine what the exit code of the driver should be.  */
diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
index e01d1ea..f558b0e 100644
--- a/gcc/lto-wrapper.c
+++ b/gcc/lto-wrapper.c
@@ -37,6 +37,7 @@ along with GCC; see the file COPYING3.  If not see
    ./ccCJuXGv.lto.ltrans.o
 */
 
+#define INCLUDE_STRING
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
@@ -48,6 +49,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "simple-object.h"
 #include "lto-section-names.h"
 #include "collect-utils.h"
+#include "opts-jobserver.h"
 
 /* Environment variable, used for passing the names of offload targets from GCC
    driver to lto-wrapper.  */
@@ -1295,32 +1297,6 @@ init_num_threads (void)
 #endif
 }
 
-/* FIXME: once using -std=c++11, we can use std::thread::hardware_concurrency.  */
-
-/* Return true when a jobserver is running and can accept a job.  */
-
-static bool
-jobserver_active_p (void)
-{
-  const char *makeflags = getenv ("MAKEFLAGS");
-  if (makeflags == NULL)
-    return false;
-
-  const char *needle = "--jobserver-auth=";
-  const char *n = strstr (makeflags, needle);
-  if (n == NULL)
-    return false;
-
-  int rfd = -1;
-  int wfd = -1;
-
-  return (sscanf (n + strlen (needle), "%d,%d", &rfd, &wfd) == 2
-	  && rfd > 0
-	  && wfd > 0
-	  && is_valid_fd (rfd)
-	  && is_valid_fd (wfd));
-}
-
 /* Execute gcc. ARGC is the number of arguments. ARGV contains the arguments. */
 
 static void
@@ -1535,10 +1511,20 @@ run_gcc (unsigned argc, char *argv[])
       auto_parallel = 0;
       parallel = 0;
     }
-  else if (!jobserver && jobserver_active_p ())
+  else
     {
-      parallel = 1;
-      jobserver = 1;
+      jobserver_info jinfo;
+      if (jobserver && !jinfo.is_active)
+	{
+	  warning (0, jinfo.error_msg.c_str ());
+	  parallel = 0;
+	  jobserver = 0;
+	}
+      else if (!jobserver && jinfo.is_active)
+	{
+	  parallel = 1;
+	  jobserver = 1;
+	}
     }
 
   if (linker_output)
@@ -1861,6 +1847,15 @@ cont:
       maybe_unlink (ltrans_output_file);
       ltrans_output_file = NULL;
 
+      if (nr > 1)
+	{
+	  jobserver_info jinfo;
+	  if (jobserver && !jinfo.is_active)
+	    warning (0, jinfo.error_msg.c_str ());
+	  else if (parallel == 0)
+	    warning (0, "using serial compilation of %d LTRANS jobs", nr);
+	}
+
       if (parallel)
 	{
 	  makefile = make_temp_file (".mk");
diff --git a/gcc/opts-common.c b/gcc/opts-common.c
index de9510a..04ae8d3 100644
--- a/gcc/opts-common.c
+++ b/gcc/opts-common.c
@@ -17,6 +17,7 @@ You should have received a copy of the GNU General Public License
 along with GCC; see the file COPYING3.  If not see
 <http://www.gnu.org/licenses/>.  */
 
+#define INCLUDE_STRING
 #include "config.h"
 #include "system.h"
 #include "intl.h"
@@ -25,6 +26,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "options.h"
 #include "diagnostic.h"
 #include "spellcheck.h"
+#include "opts-jobserver.h"
 
 static void prune_options (struct cl_decoded_option **, unsigned int *);
 
@@ -1805,3 +1807,42 @@ void prepend_xassembler_to_collect_as_options (const char *collect_as_options,
       obstack_1grow (o, '\'');
     }
 }
+
+jobserver_info::jobserver_info ()
+{
+  /* Detect jobserver and drop it if it's not working.  */
+  string js_needle = "--jobserver-auth=";
+
+  const char *envval = getenv ("MAKEFLAGS");
+  if (envval != NULL)
+    {
+      string makeflags = envval;
+      size_t n = makeflags.rfind (js_needle);
+      if (n != string::npos)
+	{
+	  if (sscanf (makeflags.c_str () + n + js_needle.size (),
+		      "%d,%d", &rfd, &wfd) == 2
+	      && rfd > 0
+	      && wfd > 0
+	      && is_valid_fd (rfd)
+	      && is_valid_fd (wfd))
+	    is_active = true;
+	  else
+	    {
+	      string dup = makeflags.substr (0, n);
+	      size_t pos = makeflags.find (' ', n);
+	      if (pos != string::npos)
+		dup += makeflags.substr (pos);
+	      skipped_makeflags = "MAKEFLAGS=" + dup;
+	      error_msg
+		= "cannot access %<" + js_needle + "%> file descriptors";
+	    }
+	}
+      error_msg = "%<" + js_needle + "%> is not present in %<MAKEFLAGS%>";
+    }
+  else
+    error_msg = "%<MAKEFLAGS%> environment variable is unset";
+
+  if (!error_msg.empty ())
+    error_msg = "jobserver is not available: " + error_msg;
+}
diff --git a/gcc/opts-jobserver.h b/gcc/opts-jobserver.h
new file mode 100644
index 0000000..68ce188
--- /dev/null
+++ b/gcc/opts-jobserver.h
@@ -0,0 +1,44 @@
+/* GNU make's jobserver related functionality.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.
+
+See dbgcnt.def for usage information.  */
+
+#ifndef GCC_JOBSERVER_H
+#define GCC_JOBSERVER_H
+
+using namespace std;
+
+struct jobserver_info
+{
+  /* Default constructor.  */
+  jobserver_info ();
+
+  /* Error message if there is a problem.  */
+  string error_msg = "";
+  /* Skipped MAKEFLAGS where --jobserver-auth is skipped.  */
+  string skipped_makeflags = "";
+  /* File descriptor for reading used for jobserver communication.  */
+  int rfd = -1;
+  /* File descriptor for writing used for jobserver communication.  */
+  int wfd = -1;
+  /* Return true if jobserver is active.  */
+  bool is_active = false;
+};
+
+#endif /* GCC_JOBSERVER_H */