Re: Ram initialization and small c.

[Steve Gehlbach]

Eric W. Biederman wrote:
> Oh.  I think I can have some answers in less than a month.  That is
> just what I have allocated for investigation.  But it will take a week
> or so to get something working well enough to compare with the inline
> tweaking approach.
>
> Plus write now I am enjoying the change of pace.

Cool, let's see how it goes.  Feed it the decode routine from nrv2b.c 
and see how it likes that. gcc is a long ways from doing this in 
registers without a major re-write, which is probably about as much work 
as your implementation in assy.  Very clever assy code, BTW.

Also I think the .S files don't have to be kept if we use a trivial post 
processing program like below.

-Steve

#!/usr/bin/perl
#
# program to process a .s file generated by gcc
# to eliminate gcc gingerbread so the file
# can be used for linuxbios.
# Also check for register spillage and use of the
# stack since this code is intended to run without
# ram.
#
# GPL for the linuxbios project
#
# by. Steve M. Gehlbach (steve @ kesa . com)
#

$ret = 0;
while (<STDIN>) {
#
# save everything and go over it
# once to check for errors
#
     $line = $_;
# get everthing up to comment
# we don't want to bail out on items
# in comments.
     $_ = (split(/#/))[0];
     next unless ($_);
#
# now check for things that indicate that
# the stack is being used, which means that gcc
# failed to fully inline code
# with no stack pushes
     &Abort if /(%esp)/;
     if (/(%ebp)/) {
         &Abort unless /%esp/;
     }
     &Abort if /\scall\s/;
     &Abort if /.Lfe2:/;
     /pushl/ && ($line = '#'.$line);
     /pop/ && ($line = '#'.$line);
     /leave/ && ($line = '#'.$line);
     /%esp/ && ($line = '#'.$line);
     /ret/ && do
         {
             # only one return should be there
             &Abort if ($ret);
             # convert the last return to a jump in case
             # ret is in middle of code; rel jump okay?
             $line =~ s/ret/jmp .Lfe1/;
             $ret++;
         };
     # save the processed line
     push @lines,$line;
}
#
# okay so print it out
#
while ($_ = shift @lines) {
     print $_;
}
exit (0);
#
# error print it with gas pseudo-ops
# and bail
#
sub Abort {
     chomp $line;
     print ".print "$line   <<< ERROR*** gcc uses stack or failed to 
inline code!"\n";
     print ".err\n";
     exit (1);
}