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Re: Fix even more merging PIC and PIE options


> On Fri, 10 Aug 2018, Jan Hubicka wrote:
> 
> > Hi,
> > this patch should fix merging of PIC and PIE options so we always resort
> > to the least common denominator of the object files compiled (i.e. 
> > linking together -fpic and -fPIE will result in -fpie binary).
> > Note that we also use information about format of output passed by linker
> > plugin so we will disable pic/pie when resulting binary is not relocatable.
> > However for shared libraries and pie we want to pick right mode that makes
> > sense.
> > 
> > I wrote simple script that tries all possible options of combining two files.
> > Mode picked is specified in the output file.
> > 
> > To support targets that default to pic/pie well, I had to also hack
> > lto_write_options to always stream what mode was used in the given file.
> > 
> > lto-bootstrapped/regtested x86_64-linux, OK?
> > 
> > Honza
> > 
> > 	PR lto/86517
> > 	* lto-opts.c (lto_write_options): Always stream PIC/PIE mode.
> > 	* lto-wrapper.c (merge_and_complain): Fix merging of PIC/PIE
> > Index: lto-opts.c
> > ===================================================================
> > --- lto-opts.c	(revision 263356)
> > +++ lto-opts.c	(working copy)
> > @@ -78,6 +78,22 @@ lto_write_options (void)
> >        && !global_options.x_flag_openacc)
> >      append_to_collect_gcc_options (&temporary_obstack, &first_p,
> >  				   "-fno-openacc");
> > +  /* Append PIC/PIE mode because its default depends on target and it is
> > +     subject of merging in lto-wrapper.  */
> > +  if ((!global_options_set.x_flag_pic || global_options.x_flag_pic == 0)
> 
> why's that checked only for flag_pic?
> Shouldn't it be consistent with flag_pie?
> 
> Isn't it so that setting either -f[no-]pic or -f[no-]pie fully specifies
> the state?  So the == 0 check is superfluous?

Yep, it is superflows. I have changed it to test if at least one option is set,
re-tested and going to commit.

OK for release branch after some soaking?
Honza

> 
> The rest of the patch looks OK to me.
> 
> Thanks,
> Richard.
> 
> > +      && !global_options_set.x_flag_pie)
> > +    {
> > +       append_to_collect_gcc_options (&temporary_obstack, &first_p,
> > +				      global_options.x_flag_pic == 2
> > +				      ? "-fPIC"
> > +				      : global_options.x_flag_pic == 1
> > +				      ? "-fpic"
> > +				      : global_options.x_flag_pie == 2
> > +				      ? "-fPIE"
> > +				      : global_options.x_flag_pie == 1
> > +				      ? "-fpie"
> > +				      : "-fno-pie");
> > +    }
> >  
> >    /* Append options from target hook and store them to offload_lto section.  */
> >    if (lto_stream_offload_p)
> > Index: lto-wrapper.c
> > ===================================================================
> > --- lto-wrapper.c	(revision 263356)
> > +++ lto-wrapper.c	(working copy)
> > @@ -408,6 +408,11 @@ merge_and_complain (struct cl_decoded_op
> >       It is a common mistake to mix few -fPIC compiled objects into otherwise
> >       non-PIC code.  We do not want to build everything with PIC then.
> >  
> > +     Similarly we merge PIE options, however in addition we keep
> > +      -fPIC + -fPIE = -fPIE
> > +      -fpic + -fPIE = -fpie
> > +      -fPIC/-fpic + -fpie = -fpie
> > +
> >       It would be good to warn on mismatches, but it is bit hard to do as
> >       we do not know what nothing translates to.  */
> >      
> > @@ -415,11 +420,38 @@ merge_and_complain (struct cl_decoded_op
> >      if ((*decoded_options)[j].opt_index == OPT_fPIC
> >          || (*decoded_options)[j].opt_index == OPT_fpic)
> >        {
> > -	if (!pic_option
> > -	    || (pic_option->value > 0) != ((*decoded_options)[j].value > 0))
> > -	  remove_option (decoded_options, j, decoded_options_count);
> > -	else if (pic_option->opt_index == OPT_fPIC
> > -		 && (*decoded_options)[j].opt_index == OPT_fpic)
> > +	/* -fno-pic in one unit implies -fno-pic everywhere.  */
> > +	if ((*decoded_options)[j].value == 0)
> > +	  j++;
> > +	/* If we have no pic option or merge in -fno-pic, we still may turn
> > +	   existing pic/PIC mode into pie/PIE if -fpie/-fPIE is present.  */
> > +	else if ((pic_option && pic_option->value == 0)
> > +		 || !pic_option)
> > +	  {
> > +	    if (pie_option)
> > +	      {
> > +		bool big = (*decoded_options)[j].opt_index == OPT_fPIC
> > +			   && pie_option->opt_index == OPT_fPIE;
> > +	        (*decoded_options)[j].opt_index = big ? OPT_fPIE : OPT_fpie;
> > +		if (pie_option->value)
> > +	          (*decoded_options)[j].canonical_option[0] = big ? "-fPIE" : "-fpie";
> > +		else
> > +	          (*decoded_options)[j].canonical_option[0] = big ? "-fno-pie" : "-fno-pie";
> > +		(*decoded_options)[j].value = pie_option->value;
> > +	        j++;
> > +	      }
> > +	    else if (pic_option)
> > +	      {
> > +	        (*decoded_options)[j] = *pic_option;
> > +	        j++;
> > +	      }
> > +	    /* We do not know if target defaults to pic or not, so just remove
> > +	       option if it is missing in one unit but enabled in other.  */
> > +	    else
> > +	      remove_option (decoded_options, j, decoded_options_count);
> > +	  }
> > +	else if (pic_option->opt_index == OPT_fpic
> > +		 && (*decoded_options)[j].opt_index == OPT_fPIC)
> >  	  {
> >  	    (*decoded_options)[j] = *pic_option;
> >  	    j++;
> > @@ -430,11 +462,42 @@ merge_and_complain (struct cl_decoded_op
> >     else if ((*decoded_options)[j].opt_index == OPT_fPIE
> >              || (*decoded_options)[j].opt_index == OPT_fpie)
> >        {
> > -	if (!pie_option
> > -	    || pie_option->value != (*decoded_options)[j].value)
> > -	  remove_option (decoded_options, j, decoded_options_count);
> > -	else if (pie_option->opt_index == OPT_fPIE
> > -		 && (*decoded_options)[j].opt_index == OPT_fpie)
> > +	/* -fno-pie in one unit implies -fno-pie everywhere.  */
> > +	if ((*decoded_options)[j].value == 0)
> > +	  j++;
> > +	/* If we have no pie option or merge in -fno-pie, we still preserve
> > +	   PIE/pie if pic/PIC is present.  */
> > +	else if ((pie_option && pie_option->value == 0)
> > +		 || !pie_option)
> > +	  {
> > +	    /* If -fPIC/-fpic is given, merge it with -fPIE/-fpie.  */
> > +	    if (pic_option)
> > +	      {
> > +		if (pic_option->opt_index == OPT_fpic
> > +		    && (*decoded_options)[j].opt_index == OPT_fPIE)
> > +		  {
> > +	            (*decoded_options)[j].opt_index = OPT_fpie;
> > +	            (*decoded_options)[j].canonical_option[0]
> > +			 = pic_option->value ? "-fpie" : "-fno-pie";
> > +		  }
> > +		else if (!pic_option->value)
> > +		  (*decoded_options)[j].canonical_option[0] = "-fno-pie";
> > +		(*decoded_options)[j].value = pic_option->value;
> > +		j++;
> > +	      }
> > +	    else if (pie_option)
> > +	      {
> > +	        (*decoded_options)[j] = *pie_option;
> > +		j++;
> > +	      }
> > +	    /* Because we always append pic/PIE options this code path should
> > +	       not happen unless the LTO object was built by old lto1 which
> > +	       did not contain that logic yet.  */
> > +	    else
> > +	      remove_option (decoded_options, j, decoded_options_count);
> > +	  }
> > +	else if (pie_option->opt_index == OPT_fpie
> > +		 && (*decoded_options)[j].opt_index == OPT_fPIE)
> >  	  {
> >  	    (*decoded_options)[j] = *pie_option;
> >  	    j++;
> > 
> 
> -- 
> Richard Biener <rguenther@suse.de>
> SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)


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