Re: [stage1][PATCH] Add gcc_assert that &global_options are not dirty modified.

["Martin Liška" <mliska@suse.cz>]

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On 3/19/20 5:13 PM, Martin Sebor wrote:
> On 3/19/20 9:32 AM, Martin Liška wrote:
>> On 3/19/20 10:09 AM, Jakub Jelinek wrote:
>>> I mean, optimize for the !flag_checking case...
>>>> Sure, I transformed both situations into heap memory allocation.
>> In gcc/c-family/c-attribs.c I faced maybe uninitialized warning when
>> I only assigned (and checked) the variable in flag_checking context.
> 

Hi Martin.

> I was mostly just curious about what was being checked and how so
> I might be misunderstanding something but it looks to me like
> the code generated by the loop below will be a very long series
> (of hundreds?) of if statements, each doing the same thing but
> each hardcoding different options names.  If that's correct, is
> there an easy way to turn that repetitive series into a loop to
> keep code (and string) size growth to a minimum?

Thank you very much for the feedback, it was useful. I realized that
the patch made a huge code bloat (mainly because of the string constants
and the fact that it didn't end quickly (with an internal_error).

The loop is here not possible because we compare struct fields.

> 
> Also, since the function prints output and the caller then aborts
> on failure, would calling internal_error for the first mismatch
> instead be more in keeping with how internal errors with additional
> output are reported?

I decided to call internal_error without string description of the error.
With that I have a reasonable code growth:

bloaty /tmp/cc1plus-after -- /tmp/cc1plus-before
      VM SIZE                     FILE SIZE
  --------------               --------------
   +0.1% +20.9Ki .text         +20.9Ki  +0.1%
   [ = ]       0 .debug_line   +2.38Ki  +0.0%
   [ = ]       0 .debug_info      +369  +0.0%
   [ = ]       0 .debug_str        +75  +0.0%
   +0.0%     +64 .rodata           +64  +0.0%
   [ = ]       0 .debug_ranges     +48  +0.0%
   +0.0%     +45 .dynstr           +45  +0.0%
   [ = ]       0 .strtab           +45  +0.0%
   +0.0%     +40 .eh_frame         +40  +0.0%
   +0.0%     +24 .dynsym           +24  +0.0%
   [ = ]       0 .symtab           +24  +0.0%
   +0.0%      +8 .eh_frame_hdr      +8  +0.0%
   +0.0%      +4 .gnu.hash          +4  +0.0%
   +0.0%      +4 .hash              +4  +0.0%
   +0.0%      +2 .gnu.version       +2  +0.0%
    +14%      +1 [LOAD [R]]         +1   +14%
   [ = ]       0 .debug_loc       -355  -0.0%
   [ = ]       0 [Unmapped]    -1.05Ki -36.5%
   +0.1% +21.0Ki TOTAL         +22.6Ki  +0.0%

So for debugging one will have to take a look at corresponding option-save.c line.
It does not seem to me a problem.

> 
> One last question/suggestion: if the efficiency of the checking is
> at all a concern, would calling memcmp on the arrays first and only
> looping to find the position of the mismatch, be viable? (I have no
> idea if changes to some of the options are acceptable; if they are
> this wouldn't work).

Well, I skip some fields in the struct and there can be string pointers, so I'm suggesting
not to use memcmp.

There's updated tested patch.
Martin

> 
> Martin
> 
> PS Since the function doesn't modify the option arrays it could
> declare them const.
> 
> diff --git a/gcc/opth-gen.awk b/gcc/opth-gen.awk
> index 856a69168a5..586213da3d3 100644
> --- a/gcc/opth-gen.awk
> +++ b/gcc/opth-gen.awk
> @@ -119,6 +119,41 @@ print "#endif"
>   print "#endif"
>   print ""
> 
> +print "#if !defined(IN_LIBGCC2) && !defined(IN_TARGET_LIBS) && !defined(IN_RTS)"
> +print "#ifndef GENERATOR_FILE"
> +print "static inline bool gcc_options_check (gcc_options *ptr1, gcc_options *ptr2)"
> +print "{"
> +print "  bool result = true;"
> +
> +# all these options are mentioned in PR92860
> +checked_options["flag_merge_constants"]++
> +checked_options["param_max_fields_for_field_sensitive"]++
> +checked_options["flag_omit_frame_pointer"]++
> +checked_options["unroll_only_small_loops"]++
> +
> +for (i = 0; i < n_opts; i++) {
> +    name = var_name(flags[i]);
> +    if (name == "")
> +        continue;
> +
> +    if (name in checked_options)
> +        continue;
> +    checked_options[name]++
> +
> +    print "  if (ptr1->x_" name " != ptr2->x_" name ")"
> +    print "  {"
> +    print "    if (result)"
> +    print "      fprintf (stderr, \"Error: global_options are modified in local context:\\n\");"
> +    print "    fprintf (stderr, \"  " name " (%ld/%ld)\\n\", (long int)ptr1->x_" name ", (long int)ptr2->x_" name ");"
> +    print "    result = false;"
> +    print "  }"
> +}
> +
> +print "  return result;"
> +print "}"
> +print "#endif"
> +print "#endif"
> +
>   # All of the optimization switches gathered together so they can be saved and restored.
>   # This will allow attribute((cold)) to turn on space optimization.
> 


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From 94f01ce8a662293dc6bc44a0e3047c5fe54fc15d Mon Sep 17 00:00:00 2001
From: Martin Liska <mliska@suse.cz>
Date: Tue, 10 Dec 2019 19:41:08 +0100
Subject: [PATCH] Add gcc_assert that &global_options are not dirty modified.

gcc/ChangeLog:

2020-03-20  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/92860
	* optc-save-gen.awk: Generate new function cl_optimization_compare.
	* opth-gen.awk: Generate declaration of the function.

gcc/c-family/ChangeLog:

2020-03-20  Martin Liska  <mliska@suse.cz>

	PR tree-optimization/92860
	* c-attribs.c (handle_optimize_attribute):
	Save global options and compare it after parsing of function
	attribute.
	* c-pragma.c (opt_stack::saved_global_options): New field.
	(handle_pragma_push_options): Save global_options.
	(handle_pragma_pop_options): Compare them after pop.
---
 gcc/c-family/c-attribs.c | 12 ++++++++++++
 gcc/c-family/c-pragma.c  | 11 +++++++++++
 gcc/optc-save-gen.awk    | 25 +++++++++++++++++++++++++
 gcc/opth-gen.awk         |  3 +++
 4 files changed, 51 insertions(+)

diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 9abf81d0248..095986dead4 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -4448,6 +4448,13 @@ handle_optimize_attribute (tree *node, tree name, tree args,
 
       /* If we previously had some optimization options, use them as the
 	 default.  */
+      gcc_options *saved_global_options = NULL;
+      if (flag_checking)
+	{
+	  saved_global_options = XNEW (gcc_options);
+	  *saved_global_options = global_options;
+	}
+
       if (old_opts)
 	cl_optimization_restore (&global_options,
 				 TREE_OPTIMIZATION (old_opts));
@@ -4459,6 +4466,11 @@ handle_optimize_attribute (tree *node, tree name, tree args,
 
       /* Restore current options.  */
       cl_optimization_restore (&global_options, &cur_opts);
+      if (saved_global_options != NULL)
+	{
+	  cl_optimization_compare (saved_global_options, &global_options);
+	  free (saved_global_options);
+	}
     }
 
   return NULL_TREE;
diff --git a/gcc/c-family/c-pragma.c b/gcc/c-family/c-pragma.c
index 7c35741745b..e3169e68fb6 100644
--- a/gcc/c-family/c-pragma.c
+++ b/gcc/c-family/c-pragma.c
@@ -1003,6 +1003,7 @@ struct GTY(()) opt_stack {
   tree target_strings;
   tree optimize_binary;
   tree optimize_strings;
+  gcc_options * GTY ((skip)) saved_global_options;
 };
 
 static GTY(()) struct opt_stack * options_stack;
@@ -1028,6 +1029,11 @@ handle_pragma_push_options (cpp_reader *ARG_UNUSED(dummy))
   options_stack = p;
 
   /* Save optimization and target flags in binary format.  */
+  if (flag_checking)
+    {
+      p->saved_global_options = XNEW (gcc_options);
+      *p->saved_global_options = global_options;
+    }
   p->optimize_binary = build_optimization_node (&global_options);
   p->target_binary = build_target_option_node (&global_options);
 
@@ -1079,6 +1085,11 @@ handle_pragma_pop_options (cpp_reader *ARG_UNUSED(dummy))
 				      p->optimize_binary);
       optimization_current_node = p->optimize_binary;
     }
+  if (flag_checking)
+    {
+      cl_optimization_compare (p->saved_global_options, &global_options);
+      free (p->saved_global_options);
+    }
 
   current_target_pragma = p->target_strings;
   current_optimize_pragma = p->optimize_strings;
diff --git a/gcc/optc-save-gen.awk b/gcc/optc-save-gen.awk
index 6033f519866..4a0e5ab64f3 100644
--- a/gcc/optc-save-gen.awk
+++ b/gcc/optc-save-gen.awk
@@ -945,5 +945,30 @@ for (i = 0; i < n_opt_val; i++) {
 	      print "    free (const_cast <char *>(ptr->" name"));";
 	}
 }
+print "}";
+
+print "void";
+print "cl_optimization_compare (gcc_options *ptr1, gcc_options *ptr2)"
+print "{"
+
+# all these options are mentioned in PR92860
+checked_options["flag_merge_constants"]++
+checked_options["param_max_fields_for_field_sensitive"]++
+checked_options["flag_omit_frame_pointer"]++
+checked_options["unroll_only_small_loops"]++
+
+for (i = 0; i < n_opts; i++) {
+	name = var_name(flags[i]);
+	if (name == "")
+		continue;
+
+	if (name in checked_options)
+		continue;
+	checked_options[name]++
+
+	print "  if (ptr1->x_" name " != ptr2->x_" name ")"
+	print "    internal_error (\"Error: global_options are modified in local context\\n\");";
+}
+
 print "}";
 }
diff --git a/gcc/opth-gen.awk b/gcc/opth-gen.awk
index 856a69168a5..472fd591413 100644
--- a/gcc/opth-gen.awk
+++ b/gcc/opth-gen.awk
@@ -318,6 +318,9 @@ print "";
 print "/* Free heap memory used by optimization options.  */";
 print "extern void cl_optimization_option_free (cl_optimization *ptr1);"
 print "";
+print "/* Compare and report difference for a part of cl_optimization options.  */";
+print "extern void cl_optimization_compare (gcc_options *ptr1, gcc_options *ptr2);";
+print "";
 print "/* Generator files may not have access to location_t, and don't need these.  */"
 print "#if defined(UNKNOWN_LOCATION)"
 print "bool                                                                  "
-- 
2.25.1