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openssl/crypto/bn/asm/x86-mont.pl
David Benjamin 32be631ca1 Do not silently truncate files on perlasm errors 
If one of the perlasm xlate drivers crashes, OpenSSL's build will
currently swallow the error and silently truncate the output to however
far the driver got. This will hopefully fail to build, but better to
check such things.

Handle this by checking for errors when closing STDOUT (which is a pipe
to the xlate driver).

Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/10883)
2020-01-22 18:11:30 +01:00

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#! /usr/bin/env perl
# Copyright 2005-2018 The OpenSSL Project Authors. All Rights Reserved.
#
# Licensed under the Apache License 2.0 (the "License"). You may not use
# this file except in compliance with the License. You can obtain a copy
# in the file LICENSE in the source distribution or at
# https://www.openssl.org/source/license.html
# ====================================================================
# Written by Andy Polyakov <appro@openssl.org> for the OpenSSL
# project. The module is, however, dual licensed under OpenSSL and
# CRYPTOGAMS licenses depending on where you obtain it. For further
# details see http://www.openssl.org/~appro/cryptogams/.
# ====================================================================
# October 2005
#
# This is a "teaser" code, as it can be improved in several ways...
# First of all non-SSE2 path should be implemented (yes, for now it
# performs Montgomery multiplication/convolution only on SSE2-capable
# CPUs such as P4, others fall down to original code). Then inner loop
# can be unrolled and modulo-scheduled to improve ILP and possibly
# moved to 128-bit XMM register bank (though it would require input
# rearrangement and/or increase bus bandwidth utilization). Dedicated
# squaring procedure should give further performance improvement...
# Yet, for being draft, the code improves rsa512 *sign* benchmark by
# 110%(!), rsa1024 one - by 70% and rsa4096 - by 20%:-)
# December 2006
#
# Modulo-scheduling SSE2 loops results in further 15-20% improvement.
# Integer-only code [being equipped with dedicated squaring procedure]
# gives ~40% on rsa512 sign benchmark...
$0 =~ m/(.*[\/\\])[^\/\\]+$/; $dir=$1;
push(@INC,"${dir}","${dir}../../perlasm");
require "x86asm.pl";
$output = pop and open STDOUT,">$output";
&asm_init($ARGV[0]);
$sse2=0;
for (@ARGV) { $sse2=1 if (/-DOPENSSL_IA32_SSE2/); }
&external_label("OPENSSL_ia32cap_P") if ($sse2);
&function_begin("bn_mul_mont");
$i="edx";
$j="ecx";
$ap="esi"; $tp="esi"; # overlapping variables!!!
$rp="edi"; $bp="edi"; # overlapping variables!!!
$np="ebp";
$num="ebx";
$_num=&DWP(4*0,"esp"); # stack top layout
$_rp=&DWP(4*1,"esp");
$_ap=&DWP(4*2,"esp");
$_bp=&DWP(4*3,"esp");
$_np=&DWP(4*4,"esp");
$_n0=&DWP(4*5,"esp"); $_n0q=&QWP(4*5,"esp");
$_sp=&DWP(4*6,"esp");
$_bpend=&DWP(4*7,"esp");
$frame=32; # size of above frame rounded up to 16n
&xor ("eax","eax");
&mov ("edi",&wparam(5)); # int num
&cmp ("edi",4);
&jl (&label("just_leave"));
&lea ("esi",&wparam(0)); # put aside pointer to argument block
&lea ("edx",&wparam(1)); # load ap
&add ("edi",2); # extra two words on top of tp
&neg ("edi");
&lea ("ebp",&DWP(-$frame,"esp","edi",4)); # future alloca($frame+4*(num+2))
&neg ("edi");
# minimize cache contention by arranging 2K window between stack
# pointer and ap argument [np is also position sensitive vector,
# but it's assumed to be near ap, as it's allocated at ~same
# time].
&mov ("eax","ebp");
&sub ("eax","edx");
&and ("eax",2047);
&sub ("ebp","eax"); # this aligns sp and ap modulo 2048
&xor ("edx","ebp");
&and ("edx",2048);
&xor ("edx",2048);
&sub ("ebp","edx"); # this splits them apart modulo 4096
&and ("ebp",-64); # align to cache line
# An OS-agnostic version of __chkstk.
#
# Some OSes (Windows) insist on stack being "wired" to
# physical memory in strictly sequential manner, i.e. if stack
# allocation spans two pages, then reference to farmost one can
# be punishable by SEGV. But page walking can do good even on
# other OSes, because it guarantees that villain thread hits
# the guard page before it can make damage to innocent one...
&mov ("eax","esp");
&sub ("eax","ebp");
&and ("eax",-4096);
&mov ("edx","esp"); # saved stack pointer!
&lea ("esp",&DWP(0,"ebp","eax"));
&mov ("eax",&DWP(0,"esp"));
&cmp ("esp","ebp");
&ja (&label("page_walk"));
&jmp (&label("page_walk_done"));
&set_label("page_walk",16);
&lea ("esp",&DWP(-4096,"esp"));
&mov ("eax",&DWP(0,"esp"));
&cmp ("esp","ebp");
&ja (&label("page_walk"));
&set_label("page_walk_done");
################################# load argument block...
&mov ("eax",&DWP(0*4,"esi"));# BN_ULONG *rp
&mov ("ebx",&DWP(1*4,"esi"));# const BN_ULONG *ap
&mov ("ecx",&DWP(2*4,"esi"));# const BN_ULONG *bp
&mov ("ebp",&DWP(3*4,"esi"));# const BN_ULONG *np
&mov ("esi",&DWP(4*4,"esi"));# const BN_ULONG *n0
#&mov ("edi",&DWP(5*4,"esi"));# int num
&mov ("esi",&DWP(0,"esi")); # pull n0[0]
&mov ($_rp,"eax"); # ... save a copy of argument block
&mov ($_ap,"ebx");
&mov ($_bp,"ecx");
&mov ($_np,"ebp");
&mov ($_n0,"esi");
&lea ($num,&DWP(-3,"edi")); # num=num-1 to assist modulo-scheduling
#&mov ($_num,$num); # redundant as $num is not reused
&mov ($_sp,"edx"); # saved stack pointer!
if($sse2) {
$acc0="mm0"; # mmx register bank layout
$acc1="mm1";
$car0="mm2";
$car1="mm3";
$mul0="mm4";
$mul1="mm5";
$temp="mm6";
$mask="mm7";
&picmeup("eax","OPENSSL_ia32cap_P");
&bt (&DWP(0,"eax"),26);
&jnc (&label("non_sse2"));
&mov ("eax",-1);
&movd ($mask,"eax"); # mask 32 lower bits
&mov ($ap,$_ap); # load input pointers
&mov ($bp,$_bp);
&mov ($np,$_np);
&xor ($i,$i); # i=0
&xor ($j,$j); # j=0
&movd ($mul0,&DWP(0,$bp)); # bp[0]
&movd ($mul1,&DWP(0,$ap)); # ap[0]
&movd ($car1,&DWP(0,$np)); # np[0]
&pmuludq($mul1,$mul0); # ap[0]*bp[0]
&movq ($car0,$mul1);
&movq ($acc0,$mul1); # I wish movd worked for
&pand ($acc0,$mask); # inter-register transfers
&pmuludq($mul1,$_n0q); # *=n0
&pmuludq($car1,$mul1); # "t[0]"*np[0]*n0
&paddq ($car1,$acc0);
&movd ($acc1,&DWP(4,$np)); # np[1]
&movd ($acc0,&DWP(4,$ap)); # ap[1]
&psrlq ($car0,32);
&psrlq ($car1,32);
&inc ($j); # j++
&set_label("1st",16);
&pmuludq($acc0,$mul0); # ap[j]*bp[0]
&pmuludq($acc1,$mul1); # np[j]*m1
&paddq ($car0,$acc0); # +=c0
&paddq ($car1,$acc1); # +=c1
&movq ($acc0,$car0);
&pand ($acc0,$mask);
&movd ($acc1,&DWP(4,$np,$j,4)); # np[j+1]
&paddq ($car1,$acc0); # +=ap[j]*bp[0];
&movd ($acc0,&DWP(4,$ap,$j,4)); # ap[j+1]
&psrlq ($car0,32);
&movd (&DWP($frame-4,"esp",$j,4),$car1); # tp[j-1]=
&psrlq ($car1,32);
&lea ($j,&DWP(1,$j));
&cmp ($j,$num);
&jl (&label("1st"));
&pmuludq($acc0,$mul0); # ap[num-1]*bp[0]
&pmuludq($acc1,$mul1); # np[num-1]*m1
&paddq ($car0,$acc0); # +=c0
&paddq ($car1,$acc1); # +=c1
&movq ($acc0,$car0);
&pand ($acc0,$mask);
&paddq ($car1,$acc0); # +=ap[num-1]*bp[0];
&movd (&DWP($frame-4,"esp",$j,4),$car1); # tp[num-2]=
&psrlq ($car0,32);
&psrlq ($car1,32);
&paddq ($car1,$car0);
&movq (&QWP($frame,"esp",$num,4),$car1); # tp[num].tp[num-1]
&inc ($i); # i++
&set_label("outer");
&xor ($j,$j); # j=0
&movd ($mul0,&DWP(0,$bp,$i,4)); # bp[i]
&movd ($mul1,&DWP(0,$ap)); # ap[0]
&movd ($temp,&DWP($frame,"esp")); # tp[0]
&movd ($car1,&DWP(0,$np)); # np[0]
&pmuludq($mul1,$mul0); # ap[0]*bp[i]
&paddq ($mul1,$temp); # +=tp[0]
&movq ($acc0,$mul1);
&movq ($car0,$mul1);
&pand ($acc0,$mask);
&pmuludq($mul1,$_n0q); # *=n0
&pmuludq($car1,$mul1);
&paddq ($car1,$acc0);
&movd ($temp,&DWP($frame+4,"esp")); # tp[1]
&movd ($acc1,&DWP(4,$np)); # np[1]
&movd ($acc0,&DWP(4,$ap)); # ap[1]
&psrlq ($car0,32);
&psrlq ($car1,32);
&paddq ($car0,$temp); # +=tp[1]
&inc ($j); # j++
&dec ($num);
&set_label("inner");
&pmuludq($acc0,$mul0); # ap[j]*bp[i]
&pmuludq($acc1,$mul1); # np[j]*m1
&paddq ($car0,$acc0); # +=c0
&paddq ($car1,$acc1); # +=c1
&movq ($acc0,$car0);
&movd ($temp,&DWP($frame+4,"esp",$j,4));# tp[j+1]
&pand ($acc0,$mask);
&movd ($acc1,&DWP(4,$np,$j,4)); # np[j+1]
&paddq ($car1,$acc0); # +=ap[j]*bp[i]+tp[j]
&movd ($acc0,&DWP(4,$ap,$j,4)); # ap[j+1]
&psrlq ($car0,32);
&movd (&DWP($frame-4,"esp",$j,4),$car1);# tp[j-1]=
&psrlq ($car1,32);
&paddq ($car0,$temp); # +=tp[j+1]
&dec ($num);
&lea ($j,&DWP(1,$j)); # j++
&jnz (&label("inner"));
&mov ($num,$j);
&pmuludq($acc0,$mul0); # ap[num-1]*bp[i]
&pmuludq($acc1,$mul1); # np[num-1]*m1
&paddq ($car0,$acc0); # +=c0
&paddq ($car1,$acc1); # +=c1
&movq ($acc0,$car0);
&pand ($acc0,$mask);
&paddq ($car1,$acc0); # +=ap[num-1]*bp[i]+tp[num-1]
&movd (&DWP($frame-4,"esp",$j,4),$car1); # tp[num-2]=
&psrlq ($car0,32);
&psrlq ($car1,32);
&movd ($temp,&DWP($frame+4,"esp",$num,4)); # += tp[num]
&paddq ($car1,$car0);
&paddq ($car1,$temp);
&movq (&QWP($frame,"esp",$num,4),$car1); # tp[num].tp[num-1]
&lea ($i,&DWP(1,$i)); # i++
&cmp ($i,$num);
&jle (&label("outer"));
&emms (); # done with mmx bank
&jmp (&label("common_tail"));
&set_label("non_sse2",16);
}
if (0) {
&mov ("esp",$_sp);
&xor ("eax","eax"); # signal "not fast enough [yet]"
&jmp (&label("just_leave"));
# While the below code provides competitive performance for
# all key lengths on modern Intel cores, it's still more
# than 10% slower for 4096-bit key elsewhere:-( "Competitive"
# means compared to the original integer-only assembler.
# 512-bit RSA sign is better by ~40%, but that's about all
# one can say about all CPUs...
} else {
$inp="esi"; # integer path uses these registers differently
$word="edi";
$carry="ebp";
&mov ($inp,$_ap);
&lea ($carry,&DWP(1,$num));
&mov ($word,$_bp);
&xor ($j,$j); # j=0
&mov ("edx",$inp);
&and ($carry,1); # see if num is even
&sub ("edx",$word); # see if ap==bp
&lea ("eax",&DWP(4,$word,$num,4)); # &bp[num]
&or ($carry,"edx");
&mov ($word,&DWP(0,$word)); # bp[0]
&jz (&label("bn_sqr_mont"));
&mov ($_bpend,"eax");
&mov ("eax",&DWP(0,$inp));
&xor ("edx","edx");
&set_label("mull",16);
&mov ($carry,"edx");
&mul ($word); # ap[j]*bp[0]
&add ($carry,"eax");
&lea ($j,&DWP(1,$j));
&adc ("edx",0);
&mov ("eax",&DWP(0,$inp,$j,4)); # ap[j+1]
&cmp ($j,$num);
&mov (&DWP($frame-4,"esp",$j,4),$carry); # tp[j]=
&jl (&label("mull"));
&mov ($carry,"edx");
&mul ($word); # ap[num-1]*bp[0]
&mov ($word,$_n0);
&add ("eax",$carry);
&mov ($inp,$_np);
&adc ("edx",0);
&imul ($word,&DWP($frame,"esp")); # n0*tp[0]
&mov (&DWP($frame,"esp",$num,4),"eax"); # tp[num-1]=
&xor ($j,$j);
&mov (&DWP($frame+4,"esp",$num,4),"edx"); # tp[num]=
&mov (&DWP($frame+8,"esp",$num,4),$j); # tp[num+1]=
&mov ("eax",&DWP(0,$inp)); # np[0]
&mul ($word); # np[0]*m
&add ("eax",&DWP($frame,"esp")); # +=tp[0]
&mov ("eax",&DWP(4,$inp)); # np[1]
&adc ("edx",0);
&inc ($j);
&jmp (&label("2ndmadd"));
&set_label("1stmadd",16);
&mov ($carry,"edx");
&mul ($word); # ap[j]*bp[i]
&add ($carry,&DWP($frame,"esp",$j,4)); # +=tp[j]
&lea ($j,&DWP(1,$j));
&adc ("edx",0);
&add ($carry,"eax");
&mov ("eax",&DWP(0,$inp,$j,4)); # ap[j+1]
&adc ("edx",0);
&cmp ($j,$num);
&mov (&DWP($frame-4,"esp",$j,4),$carry); # tp[j]=
&jl (&label("1stmadd"));
&mov ($carry,"edx");
&mul ($word); # ap[num-1]*bp[i]
&add ("eax",&DWP($frame,"esp",$num,4)); # +=tp[num-1]
&mov ($word,$_n0);
&adc ("edx",0);
&mov ($inp,$_np);
&add ($carry,"eax");
&adc ("edx",0);
&imul ($word,&DWP($frame,"esp")); # n0*tp[0]
&xor ($j,$j);
&add ("edx",&DWP($frame+4,"esp",$num,4)); # carry+=tp[num]
&mov (&DWP($frame,"esp",$num,4),$carry); # tp[num-1]=
&adc ($j,0);
&mov ("eax",&DWP(0,$inp)); # np[0]
&mov (&DWP($frame+4,"esp",$num,4),"edx"); # tp[num]=
&mov (&DWP($frame+8,"esp",$num,4),$j); # tp[num+1]=
&mul ($word); # np[0]*m
&add ("eax",&DWP($frame,"esp")); # +=tp[0]
&mov ("eax",&DWP(4,$inp)); # np[1]
&adc ("edx",0);
&mov ($j,1);
&set_label("2ndmadd",16);
&mov ($carry,"edx");
&mul ($word); # np[j]*m
&add ($carry,&DWP($frame,"esp",$j,4)); # +=tp[j]
&lea ($j,&DWP(1,$j));
&adc ("edx",0);
&add ($carry,"eax");
&mov ("eax",&DWP(0,$inp,$j,4)); # np[j+1]
&adc ("edx",0);
&cmp ($j,$num);
&mov (&DWP($frame-8,"esp",$j,4),$carry); # tp[j-1]=
&jl (&label("2ndmadd"));
&mov ($carry,"edx");
&mul ($word); # np[j]*m
&add ($carry,&DWP($frame,"esp",$num,4)); # +=tp[num-1]
&adc ("edx",0);
&add ($carry,"eax");
&adc ("edx",0);
&mov (&DWP($frame-4,"esp",$num,4),$carry); # tp[num-2]=
&xor ("eax","eax");
&mov ($j,$_bp); # &bp[i]
&add ("edx",&DWP($frame+4,"esp",$num,4)); # carry+=tp[num]
&adc ("eax",&DWP($frame+8,"esp",$num,4)); # +=tp[num+1]
&lea ($j,&DWP(4,$j));
&mov (&DWP($frame,"esp",$num,4),"edx"); # tp[num-1]=
&cmp ($j,$_bpend);
&mov (&DWP($frame+4,"esp",$num,4),"eax"); # tp[num]=
&je (&label("common_tail"));
&mov ($word,&DWP(0,$j)); # bp[i+1]
&mov ($inp,$_ap);
&mov ($_bp,$j); # &bp[++i]
&xor ($j,$j);
&xor ("edx","edx");
&mov ("eax",&DWP(0,$inp));
&jmp (&label("1stmadd"));
&set_label("bn_sqr_mont",16);
$sbit=$num;
&mov ($_num,$num);
&mov ($_bp,$j); # i=0
&mov ("eax",$word); # ap[0]
&mul ($word); # ap[0]*ap[0]
&mov (&DWP($frame,"esp"),"eax"); # tp[0]=
&mov ($sbit,"edx");
&shr ("edx",1);
&and ($sbit,1);
&inc ($j);
&set_label("sqr",16);
&mov ("eax",&DWP(0,$inp,$j,4)); # ap[j]
&mov ($carry,"edx");
&mul ($word); # ap[j]*ap[0]
&add ("eax",$carry);
&lea ($j,&DWP(1,$j));
&adc ("edx",0);
&lea ($carry,&DWP(0,$sbit,"eax",2));
&shr ("eax",31);
&cmp ($j,$_num);
&mov ($sbit,"eax");
&mov (&DWP($frame-4,"esp",$j,4),$carry); # tp[j]=
&jl (&label("sqr"));
&mov ("eax",&DWP(0,$inp,$j,4)); # ap[num-1]
&mov ($carry,"edx");
&mul ($word); # ap[num-1]*ap[0]
&add ("eax",$carry);
&mov ($word,$_n0);
&adc ("edx",0);
&mov ($inp,$_np);
&lea ($carry,&DWP(0,$sbit,"eax",2));
&imul ($word,&DWP($frame,"esp")); # n0*tp[0]
&shr ("eax",31);
&mov (&DWP($frame,"esp",$j,4),$carry); # tp[num-1]=
&lea ($carry,&DWP(0,"eax","edx",2));
&mov ("eax",&DWP(0,$inp)); # np[0]
&shr ("edx",31);
&mov (&DWP($frame+4,"esp",$j,4),$carry); # tp[num]=
&mov (&DWP($frame+8,"esp",$j,4),"edx"); # tp[num+1]=
&mul ($word); # np[0]*m
&add ("eax",&DWP($frame,"esp")); # +=tp[0]
&mov ($num,$j);
&adc ("edx",0);
&mov ("eax",&DWP(4,$inp)); # np[1]
&mov ($j,1);
&set_label("3rdmadd",16);
&mov ($carry,"edx");
&mul ($word); # np[j]*m
&add ($carry,&DWP($frame,"esp",$j,4)); # +=tp[j]
&adc ("edx",0);
&add ($carry,"eax");
&mov ("eax",&DWP(4,$inp,$j,4)); # np[j+1]
&adc ("edx",0);
&mov (&DWP($frame-4,"esp",$j,4),$carry); # tp[j-1]=
&mov ($carry,"edx");
&mul ($word); # np[j+1]*m
&add ($carry,&DWP($frame+4,"esp",$j,4)); # +=tp[j+1]
&lea ($j,&DWP(2,$j));
&adc ("edx",0);
&add ($carry,"eax");
&mov ("eax",&DWP(0,$inp,$j,4)); # np[j+2]
&adc ("edx",0);
&cmp ($j,$num);
&mov (&DWP($frame-8,"esp",$j,4),$carry); # tp[j]=
&jl (&label("3rdmadd"));
&mov ($carry,"edx");
&mul ($word); # np[j]*m
&add ($carry,&DWP($frame,"esp",$num,4)); # +=tp[num-1]
&adc ("edx",0);
&add ($carry,"eax");
&adc ("edx",0);
&mov (&DWP($frame-4,"esp",$num,4),$carry); # tp[num-2]=
&mov ($j,$_bp); # i
&xor ("eax","eax");
&mov ($inp,$_ap);
&add ("edx",&DWP($frame+4,"esp",$num,4)); # carry+=tp[num]
&adc ("eax",&DWP($frame+8,"esp",$num,4)); # +=tp[num+1]
&mov (&DWP($frame,"esp",$num,4),"edx"); # tp[num-1]=
&cmp ($j,$num);
&mov (&DWP($frame+4,"esp",$num,4),"eax"); # tp[num]=
&je (&label("common_tail"));
&mov ($word,&DWP(4,$inp,$j,4)); # ap[i]
&lea ($j,&DWP(1,$j));
&mov ("eax",$word);
&mov ($_bp,$j); # ++i
&mul ($word); # ap[i]*ap[i]
&add ("eax",&DWP($frame,"esp",$j,4)); # +=tp[i]
&adc ("edx",0);
&mov (&DWP($frame,"esp",$j,4),"eax"); # tp[i]=
&xor ($carry,$carry);
&cmp ($j,$num);
&lea ($j,&DWP(1,$j));
&je (&label("sqrlast"));
&mov ($sbit,"edx"); # zaps $num
&shr ("edx",1);
&and ($sbit,1);
&set_label("sqradd",16);
&mov ("eax",&DWP(0,$inp,$j,4)); # ap[j]
&mov ($carry,"edx");
&mul ($word); # ap[j]*ap[i]
&add ("eax",$carry);
&lea ($carry,&DWP(0,"eax","eax"));
&adc ("edx",0);
&shr ("eax",31);
&add ($carry,&DWP($frame,"esp",$j,4)); # +=tp[j]
&lea ($j,&DWP(1,$j));
&adc ("eax",0);
&add ($carry,$sbit);
&adc ("eax",0);
&cmp ($j,$_num);
&mov (&DWP($frame-4,"esp",$j,4),$carry); # tp[j]=
&mov ($sbit,"eax");
&jle (&label("sqradd"));
&mov ($carry,"edx");
&add ("edx","edx");
&shr ($carry,31);
&add ("edx",$sbit);
&adc ($carry,0);
&set_label("sqrlast");
&mov ($word,$_n0);
&mov ($inp,$_np);
&imul ($word,&DWP($frame,"esp")); # n0*tp[0]
&add ("edx",&DWP($frame,"esp",$j,4)); # +=tp[num]
&mov ("eax",&DWP(0,$inp)); # np[0]
&adc ($carry,0);
&mov (&DWP($frame,"esp",$j,4),"edx"); # tp[num]=
&mov (&DWP($frame+4,"esp",$j,4),$carry); # tp[num+1]=
&mul ($word); # np[0]*m
&add ("eax",&DWP($frame,"esp")); # +=tp[0]
&lea ($num,&DWP(-1,$j));
&adc ("edx",0);
&mov ($j,1);
&mov ("eax",&DWP(4,$inp)); # np[1]
&jmp (&label("3rdmadd"));
}
&set_label("common_tail",16);
&mov ($np,$_np); # load modulus pointer
&mov ($rp,$_rp); # load result pointer
&lea ($tp,&DWP($frame,"esp")); # [$ap and $bp are zapped]
&mov ("eax",&DWP(0,$tp)); # tp[0]
&mov ($j,$num); # j=num-1
&xor ($i,$i); # i=0 and clear CF!
&set_label("sub",16);
&sbb ("eax",&DWP(0,$np,$i,4));
&mov (&DWP(0,$rp,$i,4),"eax"); # rp[i]=tp[i]-np[i]
&dec ($j); # doesn't affect CF!
&mov ("eax",&DWP(4,$tp,$i,4)); # tp[i+1]
&lea ($i,&DWP(1,$i)); # i++
&jge (&label("sub"));
&sbb ("eax",0); # handle upmost overflow bit
&mov ("edx",-1);
&xor ("edx","eax");
&jmp (&label("copy"));
&set_label("copy",16); # conditional copy
&mov ($tp,&DWP($frame,"esp",$num,4));
&mov ($np,&DWP(0,$rp,$num,4));
&mov (&DWP($frame,"esp",$num,4),$j); # zap temporary vector
&and ($tp,"eax");
&and ($np,"edx");
&or ($np,$tp);
&mov (&DWP(0,$rp,$num,4),$np);
&dec ($num);
&jge (&label("copy"));
&mov ("esp",$_sp); # pull saved stack pointer
&mov ("eax",1);
&set_label("just_leave");
&function_end("bn_mul_mont");
&asciz("Montgomery Multiplication for x86, CRYPTOGAMS by <appro\@openssl.org>");
&asm_finish();
close STDOUT or die "error closing STDOUT";
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