--- /dev/null
+#!/usr/bin/env perl
+
+# ====================================================================
+# 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 2015
+#
+# "Teaser" Montgomery multiplication module for ARMv8. Needs more
+# work. While it does improve RSA sign performance by 20-30% (less for
+# longer keys) on most processors, for some reason RSA2048 is not
+# faster and RSA4096 goes 15-20% slower on Cortex-A57. Multiplication
+# instruction issue rate is limited on processor in question, meaning
+# that dedicated squaring procedure is a must. Well, actually all
+# contemporary AArch64 processors seem to have limited multiplication
+# issue rate, i.e. they can't issue multiplication every cycle, which
+# explains moderate improvement coefficients in comparison to
+# compiler-generated code. Recall that compiler is instructed to use
+# umulh and therefore uses same amount of multiplication instructions
+# to do the job. Assembly's edge is to minimize number of "collateral"
+# instructions and of course instruction scheduling.
+
+$flavour = shift;
+$output = shift;
+
+$0 =~ m/(.*[\/\\])[^\/\\]+$/; $dir=$1;
+( $xlate="${dir}arm-xlate.pl" and -f $xlate ) or
+( $xlate="${dir}../../perlasm/arm-xlate.pl" and -f $xlate) or
+die "can't locate arm-xlate.pl";
+
+open OUT,"| \"$^X\" $xlate $flavour $output";
+*STDOUT=*OUT;
+
+($lo0,$hi0,$aj,$m0,$alo,$ahi,
+ $lo1,$hi1,$nj,$m1,$nlo,$nhi,
+ $ovf, $i,$j,$tp,$tj) = map("x$_",6..17,19..24);
+
+# int bn_mul_mont(
+$rp="x0"; # BN_ULONG *rp,
+$ap="x1"; # const BN_ULONG *ap,
+$bp="x2"; # const BN_ULONG *bp,
+$np="x3"; # const BN_ULONG *np,
+$n0="x4"; # const BN_ULONG *n0,
+$num="x5"; # int num);
+
+$code.=<<___;
+.text
+
+.globl bn_mul_mont
+.type bn_mul_mont,%function
+.align 5
+bn_mul_mont:
+ stp x29,x30,[sp,#-64]!
+ add x29,sp,#0
+ stp x19,x20,[sp,#16]
+ stp x21,x22,[sp,#32]
+ stp x23,x24,[sp,#48]
+
+ ldr $m0,[$bp],#8 // bp[0]
+ sub $tp,sp,$num,lsl#3
+ ldp $hi0,$aj,[$ap],#16 // ap[0..1]
+ lsl $num,$num,#3
+ ldr $n0,[$n0] // *n0
+ and $tp,$tp,#-16 // ABI says so
+ ldp $hi1,$nj,[$np],#16 // np[0..1]
+
+ mul $lo0,$hi0,$m0 // ap[0]*bp[0]
+ sub $j,$num,#16 // j=num-2
+ umulh $hi0,$hi0,$m0
+ mul $alo,$aj,$m0 // ap[1]*bp[0]
+ umulh $ahi,$aj,$m0
+
+ mul $m1,$lo0,$n0 // "tp[0]"*n0
+ mov sp,$tp // alloca
+
+ mul $lo1,$hi1,$m1 // np[0]*m1
+ umulh $hi1,$hi1,$m1
+ mul $nlo,$nj,$m1 // np[1]*m1
+ adds $lo1,$lo1,$lo0 // discarded
+ umulh $nhi,$nj,$m1
+ adc $hi1,$hi1,xzr
+ cbz $j,.L1st_skip
+
+.L1st:
+ ldr $aj,[$ap],#8
+ adds $lo0,$alo,$hi0
+ sub $j,$j,#8 // j--
+ adc $hi0,$ahi,xzr
+
+ ldr $nj,[$np],#8
+ adds $lo1,$nlo,$hi1
+ mul $alo,$aj,$m0 // ap[j]*bp[0]
+ adc $hi1,$nhi,xzr
+ umulh $ahi,$aj,$m0
+
+ adds $lo1,$lo1,$lo0
+ mul $nlo,$nj,$m1 // np[j]*m1
+ adc $hi1,$hi1,xzr
+ umulh $nhi,$nj,$m1
+ str $lo1,[$tp],#8 // tp[j-1]
+ cbnz $j,.L1st
+
+.L1st_skip:
+ adds $lo0,$alo,$hi0
+ sub $ap,$ap,$num // rewind $ap
+ adc $hi0,$ahi,xzr
+
+ adds $lo1,$nlo,$hi1
+ sub $np,$np,$num // rewind $np
+ adc $hi1,$nhi,xzr
+
+ adds $lo1,$lo1,$lo0
+ sub $i,$num,#8 // i=num-1
+ adcs $hi1,$hi1,$hi0
+
+ adc $ovf,xzr,xzr // upmost overflow bit
+ stp $lo1,$hi1,[$tp]
+
+.Louter:
+ ldr $m0,[$bp],#8 // bp[i]
+ ldp $hi0,$aj,[$ap],#16
+ ldr $tj,[sp] // tp[0]
+ add $tp,sp,#8
+
+ mul $lo0,$hi0,$m0 // ap[0]*bp[i]
+ sub $j,$num,#16 // j=num-2
+ umulh $hi0,$hi0,$m0
+ ldp $hi1,$nj,[$np],#16
+ mul $alo,$aj,$m0 // ap[1]*bp[i]
+ adds $lo0,$lo0,$tj
+ umulh $ahi,$aj,$m0
+ adc $hi0,$hi0,xzr
+
+ mul $m1,$lo0,$n0
+ sub $i,$i,#8 // i--
+
+ mul $lo1,$hi1,$m1 // np[0]*m1
+ umulh $hi1,$hi1,$m1
+ mul $nlo,$nj,$m1 // np[1]*m1
+ adds $lo1,$lo1,$lo0
+ umulh $nhi,$nj,$m1
+ cbz $j,.Linner_skip
+
+.Linner:
+ ldr $aj,[$ap],#8
+ adc $hi1,$hi1,xzr
+ ldr $tj,[$tp],#8 // tp[j]
+ adds $lo0,$alo,$hi0
+ sub $j,$j,#8 // j--
+ adc $hi0,$ahi,xzr
+
+ adds $lo1,$nlo,$hi1
+ ldr $nj,[$np],#8
+ adc $hi1,$nhi,xzr
+
+ mul $alo,$aj,$m0 // ap[j]*bp[i]
+ adds $lo0,$lo0,$tj
+ umulh $ahi,$aj,$m0
+ adc $hi0,$hi0,xzr
+
+ mul $nlo,$nj,$m1 // np[j]*m1
+ adds $lo1,$lo1,$lo0
+ umulh $nhi,$nj,$m1
+ str $lo1,[$tp,#-16] // tp[j-1]
+ cbnz $j,.Linner
+
+.Linner_skip:
+ ldr $tj,[$tp],#8 // tp[j]
+ adc $hi1,$hi1,xzr
+ adds $lo0,$alo,$hi0
+ sub $ap,$ap,$num // rewind $ap
+ adc $hi0,$ahi,xzr
+
+ adds $lo1,$nlo,$hi1
+ sub $np,$np,$num // rewind $np
+ adc $hi1,$nhi,$ovf
+
+ adds $lo0,$lo0,$tj
+ adc $hi0,$hi0,xzr
+
+ adds $lo1,$lo1,$lo0
+ adcs $hi1,$hi1,$hi0
+ adc $ovf,xzr,xzr // upmost overflow bit
+ stp $lo1,$hi1,[$tp,#-16]
+
+ cbnz $i,.Louter
+
+ // Final step. We see if result is larger than modulus, and
+ // if it is, subtract the modulus. But comparison implies
+ // subtraction. So we subtract modulus, see if it borrowed,
+ // and conditionally copy original value.
+ ldr $tj,[sp] // tp[0]
+ add $tp,sp,#8
+ ldr $nj,[$np],#8 // np[0]
+ subs $j,$num,#8 // j=num-1 and clear borrow
+ mov $ap,$rp
+.Lsub:
+ sbcs $aj,$tj,$nj // tp[j]-np[j]
+ ldr $tj,[$tp],#8
+ sub $j,$j,#8 // j--
+ ldr $nj,[$np],#8
+ str $aj,[$ap],#8 // rp[j]=tp[j]-np[j]
+ cbnz $j,.Lsub
+
+ sbcs $aj,$tj,$nj
+ sbcs $ovf,$ovf,xzr // did it borrow?
+ str $aj,[$ap],#8 // rp[num-1]
+
+ ldr $tj,[sp] // tp[0]
+ add $tp,sp,#8
+ ldr $aj,[$rp],#8 // rp[0]
+ sub $num,$num,#8 // num--
+ nop
+.Lcond_copy:
+ sub $num,$num,#8 // num--
+ csel $nj,$aj,$tj,cs // did it borrow?
+ ldr $tj,[$tp],#8
+ ldr $aj,[$rp],#8
+ str xzr,[$tp,#-16] // wipe tp
+ str $nj,[$rp,#-16]
+ cbnz $num,.Lcond_copy
+
+ csel $nj,$aj,$tj,cs
+ str xzr,[$tp,#-8] // wipe tp
+ str $nj,[$rp,#-8]
+
+ ldp x19,x20,[x29,#16]
+ mov sp,x29
+ ldp x21,x22,[x29,#32]
+ ldp x23,x24,[x29,#48]
+ ldr x29,[sp],#64
+ ret
+.size bn_mul_mont,.-bn_mul_mont
+
+.asciz "Montgomery Multiplication for ARMv8, CRYPTOGAMS by <appro\@openssl.org>"
+.align 4
+___
+
+print $code;
+
+close STDOUT;
projects / openssl.git / commitdiff