offload-defaulted: Config option to silently ignore uninstalled offload compilers

If configured with --enable-offload-defaulted, configured but not installed
offload compilers and libgomp plugins are silently ignored.  Useful for
distribution compilers where those are in separate optional packages.

2021-04-28  Jakub Jelinek  <jakub@redhat.com>
	    Tobias Burnus  <tobias@codesourcery.com>

ChangeLog:

	* configure.ac (--enable-offload-defaulted): New.
	* configure: Regenerate.

gcc/ChangeLog:

	* configure.ac (OFFLOAD_DEFAULTED): AC_DEFINE if offload-defaulted.
	* gcc.c (process_command): New variable.
	(driver::maybe_putenv_OFFLOAD_TARGETS): If OFFLOAD_DEFAULTED,
	set it if -foffload is defaulted.
	* lto-wrapper.c (OFFLOAD_TARGET_DEFAULT_ENV): Define.
	(compile_offload_image): If OFFLOAD_DEFAULTED and
	OFFLOAD_TARGET_DEFAULT is in the environment, don't fail
	if corresponding mkoffload can't be found.
	(compile_images_for_offload_targets): Likewise.  Free and clear
	offload_names if no valid offload is found.
	* config.in: Regenerate.
	* configure: Regenerate.

libgomp/ChangeLog:

	* configure.ac (OFFLOAD_DEFAULTED): AC_DEFINE if offload-defaulted.
	* target.c (gomp_load_plugin_for_device): If set and if a plugin
	can't be dlopened, silently assume it has no devices.
	* Makefile.in: Regenerate.
	* config.h.in: Regenerate.
	* configure: Regenerate.

1 files changed, 16 insertions, 1 deletions

diff --git a/gcc/gcc.c b/gcc/gcc.c
index 7837553..bd561ac 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -319,6 +319,12 @@ static const char *spec_host_machine = DEFAULT_REAL_TARGET_MACHINE;
 
 static char *offload_targets = NULL;
 
+#if OFFLOAD_DEFAULTED
+/* Set to true if -foffload has not been used and offload_targets
+   is set to the configured in default.  */
+static bool offload_targets_default;
+#endif
+
 /* Nonzero if cross-compiling.
    When -b is used, the value comes from the `specs' file.  */
 
@@ -4828,7 +4834,12 @@ process_command (unsigned int decoded_options_count,
   /* If the user didn't specify any, default to all configured offload
      targets.  */
   if (ENABLE_OFFLOADING && offload_targets == NULL)
-    handle_foffload_option (OFFLOAD_TARGETS);
+    {
+      handle_foffload_option (OFFLOAD_TARGETS);
+#if OFFLOAD_DEFAULTED
+      offload_targets_default = true;
+#endif
+    }
 
   if (output_file
       && strcmp (output_file, "-") != 0
@@ -8484,6 +8495,10 @@ driver::maybe_putenv_OFFLOAD_TARGETS () const
       obstack_grow (&collect_obstack, offload_targets,
 		    strlen (offload_targets) + 1);
       xputenv (XOBFINISH (&collect_obstack, char *));
+#if OFFLOAD_DEFAULTED
+      if (offload_targets_default)
+	xputenv ("OFFLOAD_TARGET_DEFAULT=1");
+#endif
     }
 
   free (offload_targets);