[PATCH] ARM optimized SHA1 implementation

This is my ARM assembly SHA1 implementation for GIT. It is approximately
50% faster than the generic C version. On an XScale processor running at
400MHz:

	generic C version:	9.8 MB/s
	my version:		14.5 MB/s

It's not that I expect a lot of big GIT users on ARM, but I stillknow
about one important ARM user that might benefit from it, and writing
that code was fun.

I also reworked the makefile a bit so any optimized SHA1 implementations
is used regardless of whether NO_OPENSSL is defined or not.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 184 insertions, 0 deletions

diff --git a/arm/sha1_arm.S b/arm/sha1_arm.S
new file mode 100644
index 0000000000..da92d20e84
--- /dev/null
+++ b/arm/sha1_arm.S
@@ -0,0 +1,184 @@
+/*
+ *  SHA transform optimized for ARM
+ *
+ *  Copyright:	(C) 2005 by Nicolas Pitre <nico@cam.org>
+ *  Created:	September 17, 2005
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ */
+
+	.text
+	.globl	sha_transform
+
+/*
+ * void sha_transform(uint32_t *hash, const unsigned char *data, uint32_t *W);
+ *
+ * note: the "data" pointer may be unaligned.
+ */
+
+sha_transform:
+
+	stmfd	sp!, {r4 - r8, lr}
+
+	@ for (i = 0; i < 16; i++)
+	@         W[i] = ntohl(((uint32_t *)data)[i]); */
+
+#ifdef __ARMEB__
+	mov	r4, r0
+	mov	r0, r2
+	mov	r2, #64
+	bl	memcpy
+	mov	r2, r0
+	mov	r0, r4
+#else
+	mov	r3, r2
+	mov	lr, #16
+1:	ldrb	r4, [r1], #1
+	ldrb	r5, [r1], #1
+	ldrb	r6, [r1], #1
+	ldrb	r7, [r1], #1
+	subs	lr, lr, #1
+	orr	r5, r5, r4, lsl #8
+	orr	r6, r6, r5, lsl #8
+	orr	r7, r7, r6, lsl #8
+	str	r7, [r3], #4
+	bne	1b
+#endif
+
+	@ for (i = 0; i < 64; i++)
+	@         W[i+16] = ror(W[i+13] ^ W[i+8] ^ W[i+2] ^ W[i], 31);
+
+	sub	r3, r2, #4
+	mov	lr, #64
+2:	ldr	r4, [r3, #4]!
+	subs	lr, lr, #1
+	ldr	r5, [r3, #8]
+	ldr	r6, [r3, #32]
+	ldr	r7, [r3, #52]
+	eor	r4, r4, r5
+	eor	r4, r4, r6
+	eor	r4, r4, r7
+	mov	r4, r4, ror #31
+	str	r4, [r3, #64]
+	bne	2b
+
+	/*
+	 * The SHA functions are:
+	 *
+	 * f1(B,C,D) = (D ^ (B & (C ^ D)))
+	 * f2(B,C,D) = (B ^ C ^ D)
+	 * f3(B,C,D) = ((B & C) | (D & (B | C)))
+	 *
+	 * Then the sub-blocks are processed as follows:
+	 *
+	 * A' = ror(A, 27) + f(B,C,D) + E + K + *W++
+	 * B' = A
+	 * C' = ror(B, 2)
+	 * D' = C
+	 * E' = D
+	 *
+	 * We therefore unroll each loop 5 times to avoid register shuffling.
+	 * Also the ror for C (and also D and E which are successivelyderived
+	 * from it) is applied in place to cut on an additional mov insn for
+	 * each round.
+	 */
+
+	.macro	sha_f1, A, B, C, D, E
+	ldr	r3, [r2], #4
+	eor	ip, \C, \D
+	add	\E, r1, \E, ror #2
+	and	ip, \B, ip, ror #2
+	add	\E, \E, \A, ror #27
+	eor	ip, ip, \D, ror #2
+	add	\E, \E, r3
+	add	\E, \E, ip
+	.endm
+
+	.macro	sha_f2, A, B, C, D, E
+	ldr	r3, [r2], #4
+	add	\E, r1, \E, ror #2
+	eor	ip, \B, \C, ror #2
+	add	\E, \E, \A, ror #27
+	eor	ip, ip, \D, ror #2
+	add	\E, \E, r3
+	add	\E, \E, ip
+	.endm
+
+	.macro	sha_f3, A, B, C, D, E
+	ldr	r3, [r2], #4
+	add	\E, r1, \E, ror #2
+	orr	ip, \B, \C, ror #2
+	add	\E, \E, \A, ror #27
+	and	ip, ip, \D, ror #2
+	add	\E, \E, r3
+	and	r3, \B, \C, ror #2
+	orr	ip, ip, r3
+	add	\E, \E, ip
+	.endm
+
+	ldmia	r0, {r4 - r8}
+
+	mov	lr, #4
+	ldr	r1, .L_sha_K + 0
+
+	/* adjust initial values */
+	mov	r6, r6, ror #30
+	mov	r7, r7, ror #30
+	mov	r8, r8, ror #30
+
+3:	subs	lr, lr, #1
+	sha_f1	r4, r5, r6, r7, r8
+	sha_f1	r8, r4, r5, r6, r7
+	sha_f1	r7, r8, r4, r5, r6
+	sha_f1	r6, r7, r8, r4, r5
+	sha_f1	r5, r6, r7, r8, r4
+	bne	3b
+
+	ldr	r1, .L_sha_K + 4
+	mov	lr, #4
+
+4:	subs	lr, lr, #1
+	sha_f2	r4, r5, r6, r7, r8
+	sha_f2	r8, r4, r5, r6, r7
+	sha_f2	r7, r8, r4, r5, r6
+	sha_f2	r6, r7, r8, r4, r5
+	sha_f2	r5, r6, r7, r8, r4
+	bne	4b
+
+	ldr	r1, .L_sha_K + 8
+	mov	lr, #4
+
+5:	subs	lr, lr, #1
+	sha_f3	r4, r5, r6, r7, r8
+	sha_f3	r8, r4, r5, r6, r7
+	sha_f3	r7, r8, r4, r5, r6
+	sha_f3	r6, r7, r8, r4, r5
+	sha_f3	r5, r6, r7, r8, r4
+	bne	5b
+
+	ldr	r1, .L_sha_K + 12
+	mov	lr, #4
+
+6:	subs	lr, lr, #1
+	sha_f2	r4, r5, r6, r7, r8
+	sha_f2	r8, r4, r5, r6, r7
+	sha_f2	r7, r8, r4, r5, r6
+	sha_f2	r6, r7, r8, r4, r5
+	sha_f2	r5, r6, r7, r8, r4
+	bne	6b
+
+	ldmia	r0, {r1, r2, r3, ip, lr}
+	add	r4, r1, r4
+	add	r5, r2, r5
+	add	r6, r3, r6, ror #2
+	add	r7, ip, r7, ror #2
+	add	r8, lr, r8, ror #2
+	stmia	r0, {r4 - r8}
+
+	ldmfd	sp!, {r4 - r8, pc}
+
+.L_sha_K:
+	.word	0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6
+