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, 24 insertions, 2 deletions

diff --git a/gcc/lto-wrapper.c b/gcc/lto-wrapper.c
index 49894e4..e95b0d8 100644
--- a/gcc/lto-wrapper.c
+++ b/gcc/lto-wrapper.c
@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.  If not see
 /* Environment variable, used for passing the names of offload targets from GCC
    driver to lto-wrapper.  */
 #define OFFLOAD_TARGET_NAMES_ENV	"OFFLOAD_TARGET_NAMES"
+#define OFFLOAD_TARGET_DEFAULT_ENV	"OFFLOAD_TARGET_DEFAULT"
 
 /* By default there is no special suffix for target executables.  */
 #ifdef TARGET_EXECUTABLE_SUFFIX
@@ -906,6 +907,13 @@ compile_offload_image (const char *target, const char *compiler_path,
 	compiler = paths[i];
 	break;
       }
+#if OFFLOAD_DEFAULTED
+  if (!compiler && getenv (OFFLOAD_TARGET_DEFAULT_ENV))
+    {
+      free_array_of_ptrs ((void **) paths, n_paths);
+      return NULL;
+    }
+#endif
 
   if (!compiler)
     fatal_error (input_location,
@@ -976,6 +984,7 @@ compile_images_for_offload_targets (unsigned in_argc, char *in_argv[],
   if (!target_names)
     return;
   unsigned num_targets = parse_env_var (target_names, &names, NULL);
+  int next_name_entry = 0;
 
   const char *compiler_path = getenv ("COMPILER_PATH");
   if (!compiler_path)
@@ -986,15 +995,28 @@ compile_images_for_offload_targets (unsigned in_argc, char *in_argv[],
   offload_names = XCNEWVEC (char *, num_targets + 1);
   for (unsigned i = 0; i < num_targets; i++)
     {
-      offload_names[i]
+      offload_names[next_name_entry]
 	= compile_offload_image (names[i], compiler_path, in_argc, in_argv,
 				 compiler_opts, compiler_opt_count,
 				 linker_opts, linker_opt_count);
-      if (!offload_names[i])
+      if (!offload_names[next_name_entry])
+#if OFFLOAD_DEFAULTED
+	continue;
+#else
 	fatal_error (input_location,
 		     "problem with building target image for %s", names[i]);
+#endif
+      next_name_entry++;
     }
 
+#if OFFLOAD_DEFAULTED
+  if (next_name_entry == 0)
+    {
+      free (offload_names);
+      offload_names = NULL;
+    }
+#endif
+
  out:
   free_array_of_ptrs ((void **) names, num_targets);
 }