ref: 98c1cd7ae022efe276123898af6b892eade0732c
dir: /third_party/boringssl/src/crypto/fipsmodule/modes/asm/ghash-x86.pl/
#! /usr/bin/env perl
# Copyright 2010-2016 The OpenSSL Project Authors. All Rights Reserved.
#
# Licensed under the OpenSSL license (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/.
# ====================================================================
#
# March, May, June 2010
#
# The module implements "4-bit" GCM GHASH function and underlying
# single multiplication operation in GF(2^128). "4-bit" means that it
# uses 256 bytes per-key table [+64/128 bytes fixed table]. It has two
# code paths: vanilla x86 and vanilla SSE. Former will be executed on
# 486 and Pentium, latter on all others. SSE GHASH features so called
# "528B" variant of "4-bit" method utilizing additional 256+16 bytes
# of per-key storage [+512 bytes shared table]. Performance results
# are for streamed GHASH subroutine and are expressed in cycles per
# processed byte, less is better:
#
# gcc 2.95.3(*) SSE assembler x86 assembler
#
# Pentium 105/111(**) - 50
# PIII 68 /75 12.2 24
# P4 125/125 17.8 84(***)
# Opteron 66 /70 10.1 30
# Core2 54 /67 8.4 18
# Atom 105/105 16.8 53
# VIA Nano 69 /71 13.0 27
#
# (*) gcc 3.4.x was observed to generate few percent slower code,
# which is one of reasons why 2.95.3 results were chosen,
# another reason is lack of 3.4.x results for older CPUs;
# comparison with SSE results is not completely fair, because C
# results are for vanilla "256B" implementation, while
# assembler results are for "528B";-)
# (**) second number is result for code compiled with -fPIC flag,
# which is actually more relevant, because assembler code is
# position-independent;
# (***) see comment in non-MMX routine for further details;
#
# To summarize, it's >2-5 times faster than gcc-generated code. To
# anchor it to something else SHA1 assembler processes one byte in
# ~7 cycles on contemporary x86 cores. As for choice of MMX/SSE
# in particular, see comment at the end of the file...
# May 2010
#
# Add PCLMULQDQ version performing at 2.10 cycles per processed byte.
# The question is how close is it to theoretical limit? The pclmulqdq
# instruction latency appears to be 14 cycles and there can't be more
# than 2 of them executing at any given time. This means that single
# Karatsuba multiplication would take 28 cycles *plus* few cycles for
# pre- and post-processing. Then multiplication has to be followed by
# modulo-reduction. Given that aggregated reduction method [see
# "Carry-less Multiplication and Its Usage for Computing the GCM Mode"
# white paper by Intel] allows you to perform reduction only once in
# a while we can assume that asymptotic performance can be estimated
# as (28+Tmod/Naggr)/16, where Tmod is time to perform reduction
# and Naggr is the aggregation factor.
#
# Before we proceed to this implementation let's have closer look at
# the best-performing code suggested by Intel in their white paper.
# By tracing inter-register dependencies Tmod is estimated as ~19
# cycles and Naggr chosen by Intel is 4, resulting in 2.05 cycles per
# processed byte. As implied, this is quite optimistic estimate,
# because it does not account for Karatsuba pre- and post-processing,
# which for a single multiplication is ~5 cycles. Unfortunately Intel
# does not provide performance data for GHASH alone. But benchmarking
# AES_GCM_encrypt ripped out of Fig. 15 of the white paper with aadt
# alone resulted in 2.46 cycles per byte of out 16KB buffer. Note that
# the result accounts even for pre-computing of degrees of the hash
# key H, but its portion is negligible at 16KB buffer size.
#
# Moving on to the implementation in question. Tmod is estimated as
# ~13 cycles and Naggr is 2, giving asymptotic performance of ...
# 2.16. How is it possible that measured performance is better than
# optimistic theoretical estimate? There is one thing Intel failed
# to recognize. By serializing GHASH with CTR in same subroutine
# former's performance is really limited to above (Tmul + Tmod/Naggr)
# equation. But if GHASH procedure is detached, the modulo-reduction
# can be interleaved with Naggr-1 multiplications at instruction level
# and under ideal conditions even disappear from the equation. So that
# optimistic theoretical estimate for this implementation is ...
# 28/16=1.75, and not 2.16. Well, it's probably way too optimistic,
# at least for such small Naggr. I'd argue that (28+Tproc/Naggr),
# where Tproc is time required for Karatsuba pre- and post-processing,
# is more realistic estimate. In this case it gives ... 1.91 cycles.
# Or in other words, depending on how well we can interleave reduction
# and one of the two multiplications the performance should be between
# 1.91 and 2.16. As already mentioned, this implementation processes
# one byte out of 8KB buffer in 2.10 cycles, while x86_64 counterpart
# - in 2.02. x86_64 performance is better, because larger register
# bank allows to interleave reduction and multiplication better.
#
# Does it make sense to increase Naggr? To start with it's virtually
# impossible in 32-bit mode, because of limited register bank
# capacity. Otherwise improvement has to be weighed against slower
# setup, as well as code size and complexity increase. As even
# optimistic estimate doesn't promise 30% performance improvement,
# there are currently no plans to increase Naggr.
#
# Special thanks to David Woodhouse for providing access to a
# Westmere-based system on behalf of Intel Open Source Technology Centre.
# January 2010
#
# Tweaked to optimize transitions between integer and FP operations
# on same XMM register, PCLMULQDQ subroutine was measured to process
# one byte in 2.07 cycles on Sandy Bridge, and in 2.12 - on Westmere.
# The minor regression on Westmere is outweighed by ~15% improvement
# on Sandy Bridge. Strangely enough attempt to modify 64-bit code in
# similar manner resulted in almost 20% degradation on Sandy Bridge,
# where original 64-bit code processes one byte in 1.95 cycles.
#####################################################################
# For reference, AMD Bulldozer processes one byte in 1.98 cycles in
# 32-bit mode and 1.89 in 64-bit.
# February 2013
#
# Overhaul: aggregate Karatsuba post-processing, improve ILP in
# reduction_alg9. Resulting performance is 1.96 cycles per byte on
# Westmere, 1.95 - on Sandy/Ivy Bridge, 1.76 - on Bulldozer.
# This file was patched in BoringSSL to remove the variable-time 4-bit
# implementation.
$0 =~ m/(.*[\/\\])[^\/\\]+$/; $dir=$1;
push(@INC,"${dir}","${dir}../../../perlasm");
require "x86asm.pl";
$output=pop;
open STDOUT,">$output";
&asm_init($ARGV[0],$x86only = $ARGV[$#ARGV] eq "386");
$sse2=0;
for (@ARGV) { $sse2=1 if (/-DOPENSSL_IA32_SSE2/); }
if (!$x86only) {{{
if ($sse2) {{
######################################################################
# PCLMULQDQ version.
$Xip="eax";
$Htbl="edx";
$const="ecx";
$inp="esi";
$len="ebx";
($Xi,$Xhi)=("xmm0","xmm1"); $Hkey="xmm2";
($T1,$T2,$T3)=("xmm3","xmm4","xmm5");
($Xn,$Xhn)=("xmm6","xmm7");
&static_label("bswap");
sub clmul64x64_T2 { # minimal "register" pressure
my ($Xhi,$Xi,$Hkey,$HK)=@_;
&movdqa ($Xhi,$Xi); #
&pshufd ($T1,$Xi,0b01001110);
&pshufd ($T2,$Hkey,0b01001110) if (!defined($HK));
&pxor ($T1,$Xi); #
&pxor ($T2,$Hkey) if (!defined($HK));
$HK=$T2 if (!defined($HK));
&pclmulqdq ($Xi,$Hkey,0x00); #######
&pclmulqdq ($Xhi,$Hkey,0x11); #######
&pclmulqdq ($T1,$HK,0x00); #######
&xorps ($T1,$Xi); #
&xorps ($T1,$Xhi); #
&movdqa ($T2,$T1); #
&psrldq ($T1,8);
&pslldq ($T2,8); #
&pxor ($Xhi,$T1);
&pxor ($Xi,$T2); #
}
sub clmul64x64_T3 {
# Even though this subroutine offers visually better ILP, it
# was empirically found to be a tad slower than above version.
# At least in gcm_ghash_clmul context. But it's just as well,
# because loop modulo-scheduling is possible only thanks to
# minimized "register" pressure...
my ($Xhi,$Xi,$Hkey)=@_;
&movdqa ($T1,$Xi); #
&movdqa ($Xhi,$Xi);
&pclmulqdq ($Xi,$Hkey,0x00); #######
&pclmulqdq ($Xhi,$Hkey,0x11); #######
&pshufd ($T2,$T1,0b01001110); #
&pshufd ($T3,$Hkey,0b01001110);
&pxor ($T2,$T1); #
&pxor ($T3,$Hkey);
&pclmulqdq ($T2,$T3,0x00); #######
&pxor ($T2,$Xi); #
&pxor ($T2,$Xhi); #
&movdqa ($T3,$T2); #
&psrldq ($T2,8);
&pslldq ($T3,8); #
&pxor ($Xhi,$T2);
&pxor ($Xi,$T3); #
}
if (1) { # Algorithm 9 with <<1 twist.
# Reduction is shorter and uses only two
# temporary registers, which makes it better
# candidate for interleaving with 64x64
# multiplication. Pre-modulo-scheduled loop
# was found to be ~20% faster than Algorithm 5
# below. Algorithm 9 was therefore chosen for
# further optimization...
sub reduction_alg9 { # 17/11 times faster than Intel version
my ($Xhi,$Xi) = @_;
# 1st phase
&movdqa ($T2,$Xi); #
&movdqa ($T1,$Xi);
&psllq ($Xi,5);
&pxor ($T1,$Xi); #
&psllq ($Xi,1);
&pxor ($Xi,$T1); #
&psllq ($Xi,57); #
&movdqa ($T1,$Xi); #
&pslldq ($Xi,8);
&psrldq ($T1,8); #
&pxor ($Xi,$T2);
&pxor ($Xhi,$T1); #
# 2nd phase
&movdqa ($T2,$Xi);
&psrlq ($Xi,1);
&pxor ($Xhi,$T2); #
&pxor ($T2,$Xi);
&psrlq ($Xi,5);
&pxor ($Xi,$T2); #
&psrlq ($Xi,1); #
&pxor ($Xi,$Xhi) #
}
&function_begin_B("gcm_init_clmul");
&mov ($Htbl,&wparam(0));
&mov ($Xip,&wparam(1));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Hkey,&QWP(0,$Xip));
&pshufd ($Hkey,$Hkey,0b01001110);# dword swap
# <<1 twist
&pshufd ($T2,$Hkey,0b11111111); # broadcast uppermost dword
&movdqa ($T1,$Hkey);
&psllq ($Hkey,1);
&pxor ($T3,$T3); #
&psrlq ($T1,63);
&pcmpgtd ($T3,$T2); # broadcast carry bit
&pslldq ($T1,8);
&por ($Hkey,$T1); # H<<=1
# magic reduction
&pand ($T3,&QWP(16,$const)); # 0x1c2_polynomial
&pxor ($Hkey,$T3); # if(carry) H^=0x1c2_polynomial
# calculate H^2
&movdqa ($Xi,$Hkey);
&clmul64x64_T2 ($Xhi,$Xi,$Hkey);
&reduction_alg9 ($Xhi,$Xi);
&pshufd ($T1,$Hkey,0b01001110);
&pshufd ($T2,$Xi,0b01001110);
&pxor ($T1,$Hkey); # Karatsuba pre-processing
&movdqu (&QWP(0,$Htbl),$Hkey); # save H
&pxor ($T2,$Xi); # Karatsuba pre-processing
&movdqu (&QWP(16,$Htbl),$Xi); # save H^2
&palignr ($T2,$T1,8); # low part is H.lo^H.hi
&movdqu (&QWP(32,$Htbl),$T2); # save Karatsuba "salt"
&ret ();
&function_end_B("gcm_init_clmul");
&function_begin_B("gcm_gmult_clmul");
&mov ($Xip,&wparam(0));
&mov ($Htbl,&wparam(1));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Xi,&QWP(0,$Xip));
&movdqa ($T3,&QWP(0,$const));
&movups ($Hkey,&QWP(0,$Htbl));
&pshufb ($Xi,$T3);
&movups ($T2,&QWP(32,$Htbl));
&clmul64x64_T2 ($Xhi,$Xi,$Hkey,$T2);
&reduction_alg9 ($Xhi,$Xi);
&pshufb ($Xi,$T3);
&movdqu (&QWP(0,$Xip),$Xi);
&ret ();
&function_end_B("gcm_gmult_clmul");
&function_begin("gcm_ghash_clmul");
&mov ($Xip,&wparam(0));
&mov ($Htbl,&wparam(1));
&mov ($inp,&wparam(2));
&mov ($len,&wparam(3));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Xi,&QWP(0,$Xip));
&movdqa ($T3,&QWP(0,$const));
&movdqu ($Hkey,&QWP(0,$Htbl));
&pshufb ($Xi,$T3);
&sub ($len,0x10);
&jz (&label("odd_tail"));
#######
# Xi+2 =[H*(Ii+1 + Xi+1)] mod P =
# [(H*Ii+1) + (H*Xi+1)] mod P =
# [(H*Ii+1) + H^2*(Ii+Xi)] mod P
#
&movdqu ($T1,&QWP(0,$inp)); # Ii
&movdqu ($Xn,&QWP(16,$inp)); # Ii+1
&pshufb ($T1,$T3);
&pshufb ($Xn,$T3);
&movdqu ($T3,&QWP(32,$Htbl));
&pxor ($Xi,$T1); # Ii+Xi
&pshufd ($T1,$Xn,0b01001110); # H*Ii+1
&movdqa ($Xhn,$Xn);
&pxor ($T1,$Xn); #
&lea ($inp,&DWP(32,$inp)); # i+=2
&pclmulqdq ($Xn,$Hkey,0x00); #######
&pclmulqdq ($Xhn,$Hkey,0x11); #######
&pclmulqdq ($T1,$T3,0x00); #######
&movups ($Hkey,&QWP(16,$Htbl)); # load H^2
&nop ();
&sub ($len,0x20);
&jbe (&label("even_tail"));
&jmp (&label("mod_loop"));
&set_label("mod_loop",32);
&pshufd ($T2,$Xi,0b01001110); # H^2*(Ii+Xi)
&movdqa ($Xhi,$Xi);
&pxor ($T2,$Xi); #
&nop ();
&pclmulqdq ($Xi,$Hkey,0x00); #######
&pclmulqdq ($Xhi,$Hkey,0x11); #######
&pclmulqdq ($T2,$T3,0x10); #######
&movups ($Hkey,&QWP(0,$Htbl)); # load H
&xorps ($Xi,$Xn); # (H*Ii+1) + H^2*(Ii+Xi)
&movdqa ($T3,&QWP(0,$const));
&xorps ($Xhi,$Xhn);
&movdqu ($Xhn,&QWP(0,$inp)); # Ii
&pxor ($T1,$Xi); # aggregated Karatsuba post-processing
&movdqu ($Xn,&QWP(16,$inp)); # Ii+1
&pxor ($T1,$Xhi); #
&pshufb ($Xhn,$T3);
&pxor ($T2,$T1); #
&movdqa ($T1,$T2); #
&psrldq ($T2,8);
&pslldq ($T1,8); #
&pxor ($Xhi,$T2);
&pxor ($Xi,$T1); #
&pshufb ($Xn,$T3);
&pxor ($Xhi,$Xhn); # "Ii+Xi", consume early
&movdqa ($Xhn,$Xn); #&clmul64x64_TX ($Xhn,$Xn,$Hkey); H*Ii+1
&movdqa ($T2,$Xi); #&reduction_alg9($Xhi,$Xi); 1st phase
&movdqa ($T1,$Xi);
&psllq ($Xi,5);
&pxor ($T1,$Xi); #
&psllq ($Xi,1);
&pxor ($Xi,$T1); #
&pclmulqdq ($Xn,$Hkey,0x00); #######
&movups ($T3,&QWP(32,$Htbl));
&psllq ($Xi,57); #
&movdqa ($T1,$Xi); #
&pslldq ($Xi,8);
&psrldq ($T1,8); #
&pxor ($Xi,$T2);
&pxor ($Xhi,$T1); #
&pshufd ($T1,$Xhn,0b01001110);
&movdqa ($T2,$Xi); # 2nd phase
&psrlq ($Xi,1);
&pxor ($T1,$Xhn);
&pxor ($Xhi,$T2); #
&pclmulqdq ($Xhn,$Hkey,0x11); #######
&movups ($Hkey,&QWP(16,$Htbl)); # load H^2
&pxor ($T2,$Xi);
&psrlq ($Xi,5);
&pxor ($Xi,$T2); #
&psrlq ($Xi,1); #
&pxor ($Xi,$Xhi) #
&pclmulqdq ($T1,$T3,0x00); #######
&lea ($inp,&DWP(32,$inp));
&sub ($len,0x20);
&ja (&label("mod_loop"));
&set_label("even_tail");
&pshufd ($T2,$Xi,0b01001110); # H^2*(Ii+Xi)
&movdqa ($Xhi,$Xi);
&pxor ($T2,$Xi); #
&pclmulqdq ($Xi,$Hkey,0x00); #######
&pclmulqdq ($Xhi,$Hkey,0x11); #######
&pclmulqdq ($T2,$T3,0x10); #######
&movdqa ($T3,&QWP(0,$const));
&xorps ($Xi,$Xn); # (H*Ii+1) + H^2*(Ii+Xi)
&xorps ($Xhi,$Xhn);
&pxor ($T1,$Xi); # aggregated Karatsuba post-processing
&pxor ($T1,$Xhi); #
&pxor ($T2,$T1); #
&movdqa ($T1,$T2); #
&psrldq ($T2,8);
&pslldq ($T1,8); #
&pxor ($Xhi,$T2);
&pxor ($Xi,$T1); #
&reduction_alg9 ($Xhi,$Xi);
&test ($len,$len);
&jnz (&label("done"));
&movups ($Hkey,&QWP(0,$Htbl)); # load H
&set_label("odd_tail");
&movdqu ($T1,&QWP(0,$inp)); # Ii
&pshufb ($T1,$T3);
&pxor ($Xi,$T1); # Ii+Xi
&clmul64x64_T2 ($Xhi,$Xi,$Hkey); # H*(Ii+Xi)
&reduction_alg9 ($Xhi,$Xi);
&set_label("done");
&pshufb ($Xi,$T3);
&movdqu (&QWP(0,$Xip),$Xi);
&function_end("gcm_ghash_clmul");
} else { # Algorithm 5. Kept for reference purposes.
sub reduction_alg5 { # 19/16 times faster than Intel version
my ($Xhi,$Xi)=@_;
# <<1
&movdqa ($T1,$Xi); #
&movdqa ($T2,$Xhi);
&pslld ($Xi,1);
&pslld ($Xhi,1); #
&psrld ($T1,31);
&psrld ($T2,31); #
&movdqa ($T3,$T1);
&pslldq ($T1,4);
&psrldq ($T3,12); #
&pslldq ($T2,4);
&por ($Xhi,$T3); #
&por ($Xi,$T1);
&por ($Xhi,$T2); #
# 1st phase
&movdqa ($T1,$Xi);
&movdqa ($T2,$Xi);
&movdqa ($T3,$Xi); #
&pslld ($T1,31);
&pslld ($T2,30);
&pslld ($Xi,25); #
&pxor ($T1,$T2);
&pxor ($T1,$Xi); #
&movdqa ($T2,$T1); #
&pslldq ($T1,12);
&psrldq ($T2,4); #
&pxor ($T3,$T1);
# 2nd phase
&pxor ($Xhi,$T3); #
&movdqa ($Xi,$T3);
&movdqa ($T1,$T3);
&psrld ($Xi,1); #
&psrld ($T1,2);
&psrld ($T3,7); #
&pxor ($Xi,$T1);
&pxor ($Xhi,$T2);
&pxor ($Xi,$T3); #
&pxor ($Xi,$Xhi); #
}
&function_begin_B("gcm_init_clmul");
&mov ($Htbl,&wparam(0));
&mov ($Xip,&wparam(1));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Hkey,&QWP(0,$Xip));
&pshufd ($Hkey,$Hkey,0b01001110);# dword swap
# calculate H^2
&movdqa ($Xi,$Hkey);
&clmul64x64_T3 ($Xhi,$Xi,$Hkey);
&reduction_alg5 ($Xhi,$Xi);
&movdqu (&QWP(0,$Htbl),$Hkey); # save H
&movdqu (&QWP(16,$Htbl),$Xi); # save H^2
&ret ();
&function_end_B("gcm_init_clmul");
&function_begin_B("gcm_gmult_clmul");
&mov ($Xip,&wparam(0));
&mov ($Htbl,&wparam(1));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Xi,&QWP(0,$Xip));
&movdqa ($Xn,&QWP(0,$const));
&movdqu ($Hkey,&QWP(0,$Htbl));
&pshufb ($Xi,$Xn);
&clmul64x64_T3 ($Xhi,$Xi,$Hkey);
&reduction_alg5 ($Xhi,$Xi);
&pshufb ($Xi,$Xn);
&movdqu (&QWP(0,$Xip),$Xi);
&ret ();
&function_end_B("gcm_gmult_clmul");
&function_begin("gcm_ghash_clmul");
&mov ($Xip,&wparam(0));
&mov ($Htbl,&wparam(1));
&mov ($inp,&wparam(2));
&mov ($len,&wparam(3));
&call (&label("pic"));
&set_label("pic");
&blindpop ($const);
&lea ($const,&DWP(&label("bswap")."-".&label("pic"),$const));
&movdqu ($Xi,&QWP(0,$Xip));
&movdqa ($T3,&QWP(0,$const));
&movdqu ($Hkey,&QWP(0,$Htbl));
&pshufb ($Xi,$T3);
&sub ($len,0x10);
&jz (&label("odd_tail"));
#######
# Xi+2 =[H*(Ii+1 + Xi+1)] mod P =
# [(H*Ii+1) + (H*Xi+1)] mod P =
# [(H*Ii+1) + H^2*(Ii+Xi)] mod P
#
&movdqu ($T1,&QWP(0,$inp)); # Ii
&movdqu ($Xn,&QWP(16,$inp)); # Ii+1
&pshufb ($T1,$T3);
&pshufb ($Xn,$T3);
&pxor ($Xi,$T1); # Ii+Xi
&clmul64x64_T3 ($Xhn,$Xn,$Hkey); # H*Ii+1
&movdqu ($Hkey,&QWP(16,$Htbl)); # load H^2
&sub ($len,0x20);
&lea ($inp,&DWP(32,$inp)); # i+=2
&jbe (&label("even_tail"));
&set_label("mod_loop");
&clmul64x64_T3 ($Xhi,$Xi,$Hkey); # H^2*(Ii+Xi)
&movdqu ($Hkey,&QWP(0,$Htbl)); # load H
&pxor ($Xi,$Xn); # (H*Ii+1) + H^2*(Ii+Xi)
&pxor ($Xhi,$Xhn);
&reduction_alg5 ($Xhi,$Xi);
#######
&movdqa ($T3,&QWP(0,$const));
&movdqu ($T1,&QWP(0,$inp)); # Ii
&movdqu ($Xn,&QWP(16,$inp)); # Ii+1
&pshufb ($T1,$T3);
&pshufb ($Xn,$T3);
&pxor ($Xi,$T1); # Ii+Xi
&clmul64x64_T3 ($Xhn,$Xn,$Hkey); # H*Ii+1
&movdqu ($Hkey,&QWP(16,$Htbl)); # load H^2
&sub ($len,0x20);
&lea ($inp,&DWP(32,$inp));
&ja (&label("mod_loop"));
&set_label("even_tail");
&clmul64x64_T3 ($Xhi,$Xi,$Hkey); # H^2*(Ii+Xi)
&pxor ($Xi,$Xn); # (H*Ii+1) + H^2*(Ii+Xi)
&pxor ($Xhi,$Xhn);
&reduction_alg5 ($Xhi,$Xi);
&movdqa ($T3,&QWP(0,$const));
&test ($len,$len);
&jnz (&label("done"));
&movdqu ($Hkey,&QWP(0,$Htbl)); # load H
&set_label("odd_tail");
&movdqu ($T1,&QWP(0,$inp)); # Ii
&pshufb ($T1,$T3);
&pxor ($Xi,$T1); # Ii+Xi
&clmul64x64_T3 ($Xhi,$Xi,$Hkey); # H*(Ii+Xi)
&reduction_alg5 ($Xhi,$Xi);
&movdqa ($T3,&QWP(0,$const));
&set_label("done");
&pshufb ($Xi,$T3);
&movdqu (&QWP(0,$Xip),$Xi);
&function_end("gcm_ghash_clmul");
}
&set_label("bswap",64);
&data_byte(15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0);
&data_byte(1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0xc2); # 0x1c2_polynomial
}} # $sse2
}}} # !$x86only
&asciz("GHASH for x86, CRYPTOGAMS by <appro\@openssl.org>");
&asm_finish();
close STDOUT or die "error closing STDOUT: $!";
# A question was risen about choice of vanilla MMX. Or rather why wasn't
# SSE2 chosen instead? In addition to the fact that MMX runs on legacy
# CPUs such as PIII, "4-bit" MMX version was observed to provide better
# performance than *corresponding* SSE2 one even on contemporary CPUs.
# SSE2 results were provided by Peter-Michael Hager. He maintains SSE2
# implementation featuring full range of lookup-table sizes, but with
# per-invocation lookup table setup. Latter means that table size is
# chosen depending on how much data is to be hashed in every given call,
# more data - larger table. Best reported result for Core2 is ~4 cycles
# per processed byte out of 64KB block. This number accounts even for
# 64KB table setup overhead. As discussed in gcm128.c we choose to be
# more conservative in respect to lookup table sizes, but how do the
# results compare? Minimalistic "256B" MMX version delivers ~11 cycles
# on same platform. As also discussed in gcm128.c, next in line "8-bit
# Shoup's" or "4KB" method should deliver twice the performance of
# "256B" one, in other words not worse than ~6 cycles per byte. It
# should be also be noted that in SSE2 case improvement can be "super-
# linear," i.e. more than twice, mostly because >>8 maps to single
# instruction on SSE2 register. This is unlike "4-bit" case when >>4
# maps to same amount of instructions in both MMX and SSE2 cases.
# Bottom line is that switch to SSE2 is considered to be justifiable
# only in case we choose to implement "8-bit" method...