--- /dev/null
+C -*- mode: asm; asm-comment-char: ?C; -*-
+C nettle, low-level cryptographics library
+C
+C Copyright (C) 2013, Niels Möller
+C
+C The nettle library is free software; you can redistribute it and/or modify
+C it under the terms of the GNU Lesser General Public License as published by
+C the Free Software Foundation; either version 2.1 of the License, or (at your
+C option) any later version.
+C
+C The nettle library is distributed in the hope that it will be useful, but
+C WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+C or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+C License for more details.
+C
+C You should have received a copy of the GNU Lesser General Public License
+C along with the nettle library; see the file COPYING.LIB. If not, write to
+C the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+C MA 02111-1301, USA.
+
+C Register usage:
+
+define(<DST>, <r0>)
+define(<SRC>, <r1>)
+define(<N>, <r2>)
+define(<CNT>, <r6>)
+define(<TNC>, <r7>)
+
+ .syntax unified
+
+ .file "memxor.asm"
+
+ .text
+ .arm
+
+ C memxor(uint8_t *dst, const uint8_t *src, size_t n)
+ .align 2
+PROLOGUE(memxor)
+ cmp N, #0
+ beq .Lmemxor_ret
+
+ push {r4, r5, r6, r7}
+
+ cmp N, #7
+ bcs .Lmemxor_large
+
+ C Simple byte loop
+.Lmemxor_bytes:
+ ldrb r3, [SRC], #+1
+ ldrb r4, [DST]
+ eor r3, r4
+ strb r3, [DST], #+1
+ subs N, #1
+ bne .Lmemxor_bytes
+
+.Lmemxor_done:
+ pop {r4,r5,r6,r7}
+.Lmemxor_ret:
+ bx lr
+
+.Lmemxor_align_loop:
+ ldrb r3, [SRC], #+1
+ ldrb r4, [DST]
+ eor r3, r4
+ strb r3, [DST], #+1
+ sub N, #1
+
+.Lmemxor_large:
+ tst DST, #3
+ bne .Lmemxor_align_loop
+
+ C We have at least 4 bytes left to do here.
+ sub N, #4
+
+ ands CNT, SRC, #3
+ beq .Lmemxor_same
+
+ C Different alignment case.
+ C v original SRC
+ C +-------+------+
+ C |SRC |SRC+4 |
+ C +---+---+------+
+ C |DST |
+ C +-------+
+ C
+ C With little-endian, we need to do
+ C DST[i] ^= (SRC[i] >> CNT) ^ (SRC[i+1] << TNC)
+
+ lsl CNT, #3
+ bic SRC, #3
+ rsb TNC, CNT, #32
+
+ ldr r4, [SRC], #+4
+
+ tst N, #4
+ itet eq
+ moveq r5, r4
+ subne N, #4
+ beq .Lmemxor_odd
+
+.Lmemxor_word_loop:
+ ldr r5, [SRC], #+4
+ ldr r3, [DST]
+ eor r3, r3, r4, lsr CNT
+ eor r3, r3, r5, lsl TNC
+ str r3, [DST], #+4
+.Lmemxor_odd:
+ ldr r4, [SRC], #+4
+ ldr r3, [DST]
+ eor r3, r3, r5, lsr CNT
+ eor r3, r3, r4, lsl TNC
+ str r3, [DST], #+4
+ subs N, #8
+ bcs .Lmemxor_word_loop
+ adds N, #8
+ beq .Lmemxor_done
+
+ C We have TNC/8 left-over bytes in r4, high end
+ lsr r4, CNT
+ ldr r3, [DST]
+ eor r3, r4
+ C Store bytes, one by one.
+.Lmemxor_leftover:
+ strb r3, [DST], #+1
+ subs N, #1
+ beq .Lmemxor_done
+ subs TNC, #8
+ lsr r3, #8
+ bne .Lmemxor_leftover
+
+ b .Lmemxor_bytes
+
+.Lmemxor_same:
+ ldr r3, [SRC], #+4
+ ldr r4, [DST]
+ eor r3, r4
+ str r3, [DST], #+4
+
+ subs N, #4
+ bcs .Lmemxor_same
+ adds N, #4
+ beq .Lmemxor_done
+ b .Lmemxor_bytes
+EPILOGUE(memxor)
+
+define(<DST>, <r0>)
+define(<AP>, <r1>)
+define(<BP>, <r2>)
+define(<N>, <r3>)
+undefine(<CNT>)
+undefine(<TNC>)
+
+C Temporaries r4-r7
+define(<ACNT>, <r8>)
+define(<ATNC>, <r10>)
+define(<BCNT>, <r11>)
+define(<BTNC>, <r12>)
+
+ C memxor3(uint8_t *dst, const uint8_t *a, const uint8_t *b, size_t n)
+ .align 2
+PROLOGUE(memxor3)
+ cmp N, #0
+ beq .Lmemxor3_ret
+
+ push {r4,r5,r6,r7,r8,r10,r11}
+ cmp N, #7
+
+ add AP, N
+ add BP, N
+ add DST, N
+
+ bcs .Lmemxor3_large
+
+ C Simple byte loop
+.Lmemxor3_bytes:
+ ldrb r4, [AP, #-1]!
+ ldrb r5, [BP, #-1]!
+ eor r4, r5
+ strb r4, [DST, #-1]!
+ subs N, #1
+ bne .Lmemxor3_bytes
+
+.Lmemxor3_done:
+ pop {r4,r5,r6,r7,r8,r10,r11}
+.Lmemxor3_ret:
+ bx lr
+
+.Lmemxor3_align_loop:
+ ldrb r4, [AP, #-1]!
+ ldrb r5, [BP, #-1]!
+ eor r5, r4
+ strb r5, [DST, #-1]!
+ sub N, #1
+
+.Lmemxor3_large:
+ tst DST, #3
+ bne .Lmemxor3_align_loop
+
+ C We have at least 4 bytes left to do here.
+ sub N, #4
+ ands ACNT, AP, #3
+ lsl ACNT, #3
+ beq .Lmemxor3_a_aligned
+
+ ands BCNT, BP, #3
+ lsl BCNT, #3
+ bne .Lmemxor3_uu
+
+ C Swap
+ mov r4, AP
+ mov AP, BP
+ mov BP, r4
+ mov BCNT, ACNT
+
+.Lmemxor3_au:
+ C FIXME: Switch roles of A and B
+
+ C AP is aligned, BP is not
+ C v original SRC
+ C +-------+------+
+ C |SRC-4 |SRC |
+ C +---+---+------+
+ C |DST-4 |
+ C +-------+
+ C
+ C With little-endian, we need to do
+ C DST[i-i] ^= (SRC[i-i] >> CNT) ^ (SRC[i] << TNC)
+ rsb BTNC, BCNT, #32
+ bic BP, #3
+
+ ldr r4, [BP]
+
+ tst N, #4
+ itet eq
+ moveq r5, r4
+ subne N, #4
+ beq .Lmemxor3_au_odd
+
+.Lmemxor3_au_loop:
+ ldr r5, [BP, #-4]!
+ ldr r6, [AP, #-4]!
+ eor r6, r6, r4, lsl BTNC
+ eor r6, r6, r5, lsr BCNT
+ str r6, [DST, #-4]!
+.Lmemxor3_au_odd:
+ ldr r4, [BP, #-4]!
+ ldr r6, [AP, #-4]!
+ eor r6, r6, r5, lsl BTNC
+ eor r6, r6, r4, lsr BCNT
+ str r6, [DST, #-4]!
+ subs N, #8
+ bcs .Lmemxor3_au_loop
+ adds N, #8
+ beq .Lmemxor3_done
+
+ C Leftover bytes in r4, low end
+ ldr r5, [AP, #-4]
+ C FIXME: Do this with a single shift/rotate?
+ lsr r5, BTNC
+ eor r4, r5
+ ror r4, BCNT
+
+.Lmemxor3_au_leftover:
+ C Store a byte at a time
+ ror r4, #24
+ strb r4, [DST, #-1]!
+ subs N, #1
+ beq .Lmemxor3_done
+ subs BCNT, #8
+ sub AP, #1
+ bne .Lmemxor3_au_leftover
+ b .Lmemxor3_bytes
+
+.Lmemxor3_a_aligned:
+ ands BCNT, BP, #3
+ lsl BCNT, #3
+ bne .Lmemxor3_au ;
+
+ C a, b and dst all have the same alignment.
+
+.Lmemxor3_aligned_word_loop:
+ ldr r4, [AP, #-4]!
+ ldr r5, [BP, #-4]!
+ eor r4, r5
+ str r4, [DST, #-4]!
+ subs N, #4
+ bcs .Lmemxor3_aligned_word_loop
+ adds N, #4
+ beq .Lmemxor3_done
+ b .Lmemxor3_bytes
+
+.Lmemxor3_uu:
+
+ cmp ACNT, BCNT
+ bic AP, #3
+ bic BP, #3
+ rsb ATNC, ACNT, #32
+
+ bne .Lmemxor3_uud
+
+ C AP and BP are unaligned in the same way
+
+ ldr r4, [AP]
+ ldr r6, [BP]
+ eor r4, r6
+
+ tst N, #4
+ itet eq
+ moveq r5, r4
+ subne N, #4
+ beq .Lmemxor3_uu_odd
+
+.Lmemxor3_uu_loop:
+ ldr r5, [AP, #-4]!
+ ldr r6, [BP, #-4]!
+ eor r5, r6
+ lsl r4, ATNC
+ eor r4, r4, r5, lsr ACNT
+ str r4, [DST, #-4]!
+.Lmemxor3_uu_odd:
+ ldr r4, [AP, #-4]!
+ ldr r6, [BP, #-4]!
+ eor r4, r6
+ lsl r5, ATNC
+ eor r5, r5, r4, lsr ACNT
+ str r5, [DST, #-4]!
+ subs N, #8
+ bcs .Lmemxor3_uu_loop
+ adds N, #8
+ beq .Lmemxor3_done
+
+ C Leftover bytes in a4, low end
+ ror r4, ACNT
+.Lmemxor3_uu_leftover:
+ ror r4, #24
+ strb r4, [DST, #-1]!
+ subs N, #1
+ beq .Lmemxor3_done
+ subs ACNT, #8
+ bne .Lmemxor3_uu_leftover
+ b .Lmemxor3_bytes
+
+.Lmemxor3_uud:
+ C Both AP and BP unaligned, and in different ways
+ rsb BTNC, BCNT, #32
+
+ ldr r4, [AP]
+ ldr r6, [BP]
+
+ tst N, #4
+ ittet eq
+ moveq r5, r4
+ moveq r7, r6
+ subne N, #4
+ beq .Lmemxor3_uud_odd
+
+.Lmemxor3_uud_loop:
+ ldr r5, [AP, #-4]!
+ ldr r7, [BP, #-4]!
+ lsl r4, ATNC
+ eor r4, r4, r6, lsl BTNC
+ eor r4, r4, r5, lsr ACNT
+ eor r4, r4, r7, lsr BCNT
+ str r4, [DST, #-4]!
+.Lmemxor3_uud_odd:
+ ldr r4, [AP, #-4]!
+ ldr r6, [BP, #-4]!
+ lsl r5, ATNC
+ eor r5, r5, r7, lsl BTNC
+ eor r5, r5, r4, lsr ACNT
+ eor r5, r5, r6, lsr BCNT
+ str r5, [DST, #-4]!
+ subs N, #8
+ bcs .Lmemxor3_uud_loop
+ adds N, #8
+ beq .Lmemxor3_done
+
+ C FIXME: More clever left-over handling? For now, just adjust pointers.
+ add AP, AP, ACNT, lsr #3
+ add BP, BP, BCNT, lsr #3
+ b .Lmemxor3_bytes
+EPILOGUE(memxor3)
projects / thirdparty / nettle.git / commitdiff
