plugins: Allow plugins to handle global_options changes

Any time somebody adds or removes an option in some *.opt file (which e.g.
on the 10 branch after branching off 11 happened 7 times already), many
offsets in global_options variable change and so plugins that ever access
GCC options or other global_options values are ABI dependent on it.  It is
true we don't guarantee ABI stability for plugins, but we change the most
often used data structures on the release branches only very rarely and so
the options changes are the most problematic for ABI stability of plugins.

Annobin uses a way to remap accesses to some of the global_options.x_* by
looking them up in the cl_options array where we have
offsetof (struct gcc_options, x_flag_lto)
etc. remembered, but sadly doesn't do it for all options (e.g. some flag_*
etc. option accesses may be hidden in various macros like POINTER_SIZE),
and more importantly some struct gcc_options offsets are not covered at all.
E.g. there is no offsetof (struct gcc_options, x_optimize),
offsetof (struct gcc_options, x_flag_sanitize) etc.  Those are usually:
Variable
int optimize
in the *.opt files.

The following patch allows the plugins to deal with reshuffling of even
the global_options fields that aren't tracked in cl_options by adding
another array that describes those, which adds an 816 bytes long array
and 1039 bytes in string literals, so 1855 .rodata bytes in total ATM.
And adds it only if --enable-plugin (the default), with --disable-plugin
it will not be compiled in.

2020-11-18  Jakub Jelinek  <jakub@redhat.com>

	* opts.h (struct cl_var): New type.
	(cl_vars): Declare.
	* optc-gen.awk: Generate cl_vars array.

diff --git a/gcc/optc-gen.awk b/gcc/optc-gen.awk
index 9e7e9970395d38656ab4f9cb29615762692c0e49..be5566b960a259b134db748a5e2e1978f35605dc 100644 (file)
--- a/gcc/optc-gen.awk
+++ b/gcc/optc-gen.awk
@@ -595,5 +595,29 @@ for (i = 0; i < n_opts; i++) {
 }
 print "}               "
 
+split("", var_seen, ":")
+print "\n#if !defined(GENERATOR_FILE) && defined(ENABLE_PLUGIN)"
+print "DEBUG_VARIABLE const struct cl_var cl_vars[] =\n{"
+
+for (i = 0; i < n_opts; i++) {
+       name = var_name(flags[i]);
+       if (name == "")
+               continue;
+       var_seen[name] = 1;
 }
 
+for (i = 0; i < n_extra_vars; i++) {
+       var = extra_vars[i]
+       sub(" *=.*", "", var)
+       name = var
+       sub("^.*[ *]", "", name)
+       sub("\\[.*\\]$", "", name)
+       if (name in var_seen)
+               continue;
+       print "  { " quote name quote ", offsetof (struct gcc_options, x_" name ") },"
+       var_seen[name] = 1
+}
+
+print "  { NULL, (unsigned short) -1 }\n};\n#endif"
+
+}

diff --git a/gcc/opts.h b/gcc/opts.h
index 7d1e126f217cbe80a19feaa5cc5434b9839529d1..d62bfcfdf6af1dcdfc3c94e4401ee9fbab63e6a9 100644 (file)
--- a/gcc/opts.h
+++ b/gcc/opts.h
@@ -124,6 +124,14 @@ struct cl_option
   int range_max;
 };
 
+struct cl_var
+{
+  /* Name of the variable.  */
+  const char *var_name;
+  /* Offset of field for this var in struct gcc_options.  */
+  unsigned short var_offset;
+};
+
 /* Records that the state of an option consists of SIZE bytes starting
    at DATA.  DATA might point to CH in some cases.  */
 struct cl_option_state {
@@ -134,6 +142,9 @@ struct cl_option_state {
 
 extern const struct cl_option cl_options[];
 extern const unsigned int cl_options_count;
+#ifdef ENABLE_PLUGIN
+extern const struct cl_var cl_vars[];
+#endif
 extern const char *const lang_names[];
 extern const unsigned int cl_lang_count;