Re: [PATCH] Fix PR50999, serialize frontend specific flags (-fexceptions)

[Richard Guenther <rguenther at suse dot de>]

On Tue, 8 Nov 2011, Joseph S. Myers wrote:

> On Mon, 7 Nov 2011, Richard Guenther wrote:
> 
> > Joseph, do you have any advise on how to address frontend specific
> > options in a more general way?  I'm trying to re-construct a
> > command-line that when processed frontend agnostic would produce
> > the same end-result in global_options as if going through the frontend.
> > Is that even possible (do you have option examples that would show
> > this is impossible?)
> 
> Reconstructing command lines is never going to be particularly reliable.  
> I think the short-term fix will be saving these particular options 
> explicitly, and the longer-term fix will be representing them (anything 
> affecting IR semantics rather than just what IR gets generated) in the IR 
> so that once the front end is finished the global settings never get used.  
> (That doesn't mean moving them all to the individual GIMPLE operations, 
> although for complex-method that would be the best location; moving them 
> to struct function, with appropriate code to stream the new fields and do 
> whatever's appropriate when inlining between functions with different 
> settings, would still be useful.)

Ok, yes - that's the general direction.

I've modified the patch to use global_options again and checked in
the following.

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Richard.

2011-11-08  Richard Guenther  <rguenther@suse.de>

	PR lto/50999
	* lto-opts.c (append_to_collect_gcc_options): Split out from...
	(lto_write_options): ... here.  Prepend frontend specific flags.

Index: gcc/lto-opts.c
===================================================================
*** gcc/lto-opts.c	(revision 181150)
--- gcc/lto-opts.c	(working copy)
*************** along with GCC; see the file COPYING3.
*** 35,40 ****
--- 35,63 ----
  #include "lto-streamer.h"
  #include "toplev.h"
  
+ /* Append the option piece OPT to the COLLECT_GCC_OPTIONS string
+    set up by OB, appropriately quoted and separated by spaces
+    (if !*FIRST_P).  */
+ 
+ static void
+ append_to_collect_gcc_options (struct obstack *ob,
+ 			       bool *first_p, const char *opt)
+ {
+   const char *p, *q = opt;
+   if (!first_p)
+     obstack_grow (ob, " ", 1);
+   obstack_grow (ob, "'", 1);
+   while ((p = strchr (q, '\'')))
+     {
+       obstack_grow (ob, q, p - q);
+       obstack_grow (ob, "'\\''", 4);
+       q = ++p;
+     }
+   obstack_grow (ob, q, strlen (q));
+   obstack_grow (ob, "'", 1);
+   *first_p = false;
+ }
+ 
  /* Write currently held options to an LTO IL section.  */
  
  void
*************** lto_write_options (void)
*** 45,60 ****
    struct obstack temporary_obstack;
    unsigned int i, j;
    char *args;
  
    section_name = lto_get_section_name (LTO_section_opts, NULL, NULL);
    lto_begin_section (section_name, false);
    memset (&stream, 0, sizeof (stream));
  
    obstack_init (&temporary_obstack);
    for (i = 1; i < save_decoded_options_count; ++i)
      {
        struct cl_decoded_option *option = &save_decoded_options[i];
-       const char *q, *p;
  
        /* Skip frontend and driver specific options here.  */
        if (!(cl_options[option->opt_index].flags & (CL_COMMON|CL_TARGET|CL_LTO)))
--- 68,97 ----
    struct obstack temporary_obstack;
    unsigned int i, j;
    char *args;
+   bool first_p = true;
  
    section_name = lto_get_section_name (LTO_section_opts, NULL, NULL);
    lto_begin_section (section_name, false);
    memset (&stream, 0, sizeof (stream));
  
    obstack_init (&temporary_obstack);
+ 
+   /* Output options that affect GIMPLE IL semantics and are implicitely
+      enabled by the frontend.
+      This for now includes an explicit set of options that we also handle
+      explicitly in lto-wrapper.c.  In the end the effects on GIMPLE IL
+      semantics should be explicitely encoded in the IL or saved per
+      function rather than per compilation unit.  */
+   /* -fexceptions causes the EH machinery to be initialized, enabling
+      generation of unwind data so that explicit throw() calls work.  */
+   if (global_options.x_flag_exceptions)
+     append_to_collect_gcc_options (&temporary_obstack, &first_p,
+ 				   "-fexceptions");
+ 
+   /* Output explicitely passed options.  */
    for (i = 1; i < save_decoded_options_count; ++i)
      {
        struct cl_decoded_option *option = &save_decoded_options[i];
  
        /* Skip frontend and driver specific options here.  */
        if (!(cl_options[option->opt_index].flags & (CL_COMMON|CL_TARGET|CL_LTO)))
*************** lto_write_options (void)
*** 82,113 ****
  	  break;
  	}
  
!       if (i != 1)
! 	obstack_grow (&temporary_obstack, " ", 1);
!       obstack_grow (&temporary_obstack, "'", 1);
!       q = option->canonical_option[0];
!       while ((p = strchr (q, '\'')))
! 	{
! 	  obstack_grow (&temporary_obstack, q, p - q);
! 	  obstack_grow (&temporary_obstack, "'\\''", 4);
! 	  q = ++p;
! 	}
!       obstack_grow (&temporary_obstack, q, strlen (q));
!       obstack_grow (&temporary_obstack, "'", 1);
! 
!       for (j = 1; j < option->canonical_option_num_elements; ++j)
! 	{
! 	  obstack_grow (&temporary_obstack, " '", 2);
! 	  q = option->canonical_option[j];
! 	  while ((p = strchr (q, '\'')))
! 	    {
! 	      obstack_grow (&temporary_obstack, q, p - q);
! 	      obstack_grow (&temporary_obstack, "'\\''", 4);
! 	      q = ++p;
! 	    }
! 	  obstack_grow (&temporary_obstack, q, strlen (q));
! 	  obstack_grow (&temporary_obstack, "'", 1);
! 	}
      }
    obstack_grow (&temporary_obstack, "\0", 1);
    args = XOBFINISH (&temporary_obstack, char *);
--- 119,127 ----
  	  break;
  	}
  
!       for (j = 0; j < option->canonical_option_num_elements; ++j)
! 	append_to_collect_gcc_options (&temporary_obstack, &first_p,
! 				       option->canonical_option[j]);
      }
    obstack_grow (&temporary_obstack, "\0", 1);
    args = XOBFINISH (&temporary_obstack, char *);