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Date: Fri,  1 Mar 2013 14:24:50 +1300
From: Andre Renaud <andre@...ewatersys.com>
To: musl@...ts.openwall.com
Cc: Andre Renaud <andre@...ewatersys.com>
Subject: [PATCH] Added ARM optimised memcpy implementation

Based on Android Bionic, available from https://github.com/android/platform_bionic/

Signed-off-by: Andre Renaud <andre@...ewatersys.com>
---
 src/string/arm/memcpy.s |  369 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 369 insertions(+)
 create mode 100644 src/string/arm/memcpy.s

diff --git a/src/string/arm/memcpy.s b/src/string/arm/memcpy.s
new file mode 100644
index 0000000..e3cace9
--- /dev/null
+++ b/src/string/arm/memcpy.s
@@ -0,0 +1,369 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+
+/*
+ * Optimized memcpy() for ARM.
+ *
+ * note that memcpy() always returns the destination pointer,
+ * so we have to preserve R0.
+  */
+
+.global memcpy
+memcpy:
+	/* The stack must always be 64-bits aligned to be compliant with the
+	 * ARM ABI. Since we have to save R0, we might as well save R4
+	 * which we can use for better pipelining of the reads below
+	 */
+        .fnstart
+        .save       {r0, r4, lr}
+        stmfd       sp!, {r0, r4, lr}
+        /* Making room for r5-r11 which will be spilled later */
+        .pad        #28
+        sub         sp, sp, #28
+
+        /* it simplifies things to take care of len<4 early */
+        cmp	r2, #4
+        blo	copy_last_3_and_return
+
+        /* compute the offset to align the source
+         * offset = (4-(src&3))&3 = -src & 3
+         */
+        rsb	r3, r1, #0
+        ands	r3, r3, #3
+        beq	src_aligned
+
+        /* align source to 32 bits. We need to insert 2 instructions between
+         * a ldr[b|h] and str[b|h] because byte and half-word instructions
+         * stall 2 cycles.
+         */
+        movs	r12, r3, lsl #31
+        sub	r2, r2, r3		/* we know that r3 <= r2 because r2 >= 4 */
+        ldrmib	r3, [r1], #1
+        ldrcsb	r4, [r1], #1
+        ldrcsb	r12,[r1], #1
+        strmib	r3, [r0], #1
+        strcsb	r4, [r0], #1
+        strcsb	r12,[r0], #1
+
+src_aligned:
+
+	/* see if src and dst are aligned together (congruent) */
+	eor	r12, r0, r1
+        tst	r12, #3
+        bne	non_congruent
+
+        /* Use post-incriment mode for stm to spill r5-r11 to reserved stack
+         * frame. Don't update sp.
+         */
+        stmea	sp, {r5-r11}
+
+        /* align the destination to a cache-line */
+        rsb	r3, r0, #0
+        ands	r3, r3, #0x1C
+        beq    	congruent_aligned32
+        cmp    	r3, r2
+        andhi	r3, r2, #0x1C
+
+        /* conditionnaly copies 0 to 7 words (length in r3) */
+        movs	r12, r3, lsl #28
+        ldmcsia	r1!, {r4, r5, r6, r7}	/* 16 bytes */
+        ldmmiia	r1!, {r8, r9}			/*  8 bytes */
+        stmcsia	r0!, {r4, r5, r6, r7}
+        stmmiia	r0!, {r8, r9}
+        tst    	r3, #0x4
+        ldrne	r10,[r1], #4			/*  4 bytes */
+        strne	r10,[r0], #4
+        sub    	r2, r2, r3
+
+congruent_aligned32:
+	/*
+ 	 * here source is aligned to 32 bytes.
+ 	 */
+
+cached_aligned32:
+        subs   	r2, r2, #32
+        blo    	less_than_32_left
+
+        /*
+         * We preload a cache-line up to 64 bytes ahead. On the 926, this will
+         * stall only until the requested world is fetched, but the linefill
+         * continues in the the background.
+         * While the linefill is going, we write our previous cache-line
+         * into the write-buffer (which should have some free space).
+         * When the linefill is done, the writebuffer will
+         * start dumping its content into memory
+         *
+         * While all this is going, we then load a full cache line into
+         * 8 registers, this cache line should be in the cache by now
+         * (or partly in the cache).
+         *
+         * This code should work well regardless of the source/dest alignment.
+         *
+         */
+
+        /* Align the preload register to a cache-line because the cpu does
+         * "critical word first" (the first word requested is loaded first).
+         */
+        bic    	r12, r1, #0x1F
+        add    	r12, r12, #64
+
+1:      ldmia  	r1!, { r4-r11 }
+        subs   	r2, r2, #32
+
+        /* 
+         * NOTE: if r12 is more than 64 ahead of r1, the following ldrhi
+         * for ARM9 preload will not be safely guarded by the preceding subs.
+         * When it is safely guarded the only possibility to have SIGSEGV here
+         * is because the caller overstates the length.
+         */
+        ldrhi  	r3, [r12], #32      /* cheap ARM9 preload */
+        stmia  	r0!, { r4-r11 }
+	bhs    	1b
+
+        add	r2, r2, #32
+
+less_than_32_left:
+	/*
+	 * less than 32 bytes left at this point (length in r2)
+	 */
+
+	/* skip all this if there is nothing to do, which should
+	 * be a common case (if not executed the code below takes
+	 * about 16 cycles)
+	 */
+	tst	r2, #0x1F
+        beq	1f
+
+        /* conditionnaly copies 0 to 31 bytes */
+        movs	r12, r2, lsl #28
+        ldmcsia	r1!, {r4, r5, r6, r7}	/* 16 bytes */
+        ldmmiia	r1!, {r8, r9}			/*  8 bytes */
+        stmcsia	r0!, {r4, r5, r6, r7}
+        stmmiia	r0!, {r8, r9}
+        movs	r12, r2, lsl #30
+        ldrcs	r3, [r1], #4			/*  4 bytes */
+        ldrmih	r4, [r1], #2			/*  2 bytes */
+        strcs	r3, [r0], #4
+        strmih	r4, [r0], #2
+        tst    	r2, #0x1
+        ldrneb	r3, [r1]				/*  last byte  */
+        strneb	r3, [r0]
+
+        /* we're done! restore everything and return */
+1:	ldmfd	sp!, {r5-r11}
+        ldmfd	sp!, {r0, r4, lr}
+        bx	lr
+
+	/********************************************************************/
+
+non_congruent:
+	/*
+	 * here source is aligned to 4 bytes
+	 * but destination is not.
+	 *
+	 * in the code below r2 is the number of bytes read
+	 * (the number of bytes written is always smaller, because we have
+	 * partial words in the shift queue)
+	 */
+	cmp	r2, #4
+	blo	copy_last_3_and_return
+
+        /* Use post-incriment mode for stm to spill r5-r11 to reserved stack
+         * frame. Don't update sp.
+         */
+        stmea	sp, {r5-r11}
+
+        /* compute shifts needed to align src to dest */
+        rsb	r5, r0, #0
+        and	r5, r5, #3			/* r5 = # bytes in partial words */
+        mov	r12, r5, lsl #3		/* r12 = right */
+        rsb	lr, r12, #32		/* lr = left  */
+
+        /* read the first word */
+        ldr	r3, [r1], #4
+        sub	r2, r2, #4
+
+        /* write a partial word (0 to 3 bytes), such that destination
+         * becomes aligned to 32 bits (r5 = nb of words to copy for alignment)
+         */
+        movs	r5, r5, lsl #31
+        strmib	r3, [r0], #1
+        movmi	r3, r3, lsr #8
+        strcsb	r3, [r0], #1
+        movcs	r3, r3, lsr #8
+        strcsb	r3, [r0], #1
+        movcs	r3, r3, lsr #8
+
+        cmp	r2, #4
+        blo	partial_word_tail
+
+        /* Align destination to 32 bytes (cache line boundary) */
+1:	tst	r0, #0x1c
+        beq	2f
+        ldr	r5, [r1], #4
+        sub    	r2, r2, #4
+        orr	r4, r3, r5,		lsl lr
+        mov	r3, r5,			lsr r12
+        str	r4, [r0], #4
+        cmp    	r2, #4
+        bhs	1b
+        blo	partial_word_tail
+
+	/* copy 32 bytes at a time */
+2:	subs	r2, r2, #32
+	blo	less_than_thirtytwo
+
+        /* Use immediate mode for the shifts, because there is an extra cycle
+         * for register shifts, which could account for up to 50% of
+         * performance hit.
+         */
+
+        cmp	r12, #24
+        beq	loop24
+        cmp	r12, #8
+        beq	loop8
+
+loop16:
+        ldr    	r12, [r1], #4
+1:      mov    	r4, r12
+	ldmia	r1!, {   r5,r6,r7,  r8,r9,r10,r11}
+        subs   	r2, r2, #32
+        ldrhs  	r12, [r1], #4
+	orr	r3, r3, r4, lsl #16
+        mov	r4, r4, lsr #16
+        orr	r4, r4, r5, lsl #16
+        mov	r5, r5, lsr #16
+        orr	r5, r5, r6, lsl #16
+        mov	r6, r6, lsr #16
+        orr	r6, r6, r7, lsl #16
+        mov	r7, r7, lsr #16
+        orr	r7, r7, r8, lsl #16
+        mov	r8, r8, lsr #16
+        orr	r8, r8, r9, lsl #16
+        mov	r9, r9, lsr #16
+        orr	r9, r9, r10, lsl #16
+        mov	r10, r10,		lsr #16
+        orr	r10, r10, r11, lsl #16
+        stmia	r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
+        mov	r3, r11, lsr #16
+        bhs	1b
+        b	less_than_thirtytwo
+
+loop8:
+        ldr    	r12, [r1], #4
+1:      mov    	r4, r12
+	ldmia	r1!, {   r5,r6,r7,  r8,r9,r10,r11}
+	subs	r2, r2, #32
+        ldrhs  	r12, [r1], #4
+        orr	r3, r3, r4, lsl #24
+        mov	r4, r4, lsr #8
+        orr	r4, r4, r5, lsl #24
+        mov	r5, r5, lsr #8
+        orr	r5, r5, r6, lsl #24
+        mov	r6, r6,	 lsr #8
+        orr	r6, r6, r7, lsl #24
+        mov	r7, r7,	 lsr #8
+        orr	r7, r7, r8,		lsl #24
+        mov	r8, r8,	 lsr #8
+        orr	r8, r8, r9,		lsl #24
+        mov	r9, r9,	 lsr #8
+        orr	r9, r9, r10,	lsl #24
+        mov	r10, r10, lsr #8
+        orr	r10, r10, r11,	lsl #24
+        stmia	r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
+        mov	r3, r11, lsr #8
+        bhs	1b
+        b	less_than_thirtytwo
+
+loop24:
+        ldr    	r12, [r1], #4
+1:      mov    	r4, r12
+	ldmia	r1!, {   r5,r6,r7,  r8,r9,r10,r11}
+        subs	r2, r2, #32
+        ldrhs  	r12, [r1], #4
+        orr	r3, r3, r4, lsl #8
+        mov	r4, r4, lsr #24
+        orr	r4, r4, r5, lsl #8
+        mov	r5, r5, lsr #24
+        orr	r5, r5, r6, lsl #8
+        mov	r6, r6, lsr #24
+        orr	r6, r6, r7, lsl #8
+        mov	r7, r7, lsr #24
+        orr	r7, r7, r8, lsl #8
+        mov	r8, r8, lsr #24
+        orr	r8, r8, r9, lsl #8
+        mov	r9, r9, lsr #24
+        orr	r9, r9, r10, lsl #8
+        mov	r10, r10, lsr #24
+        orr	r10, r10, r11, lsl #8
+        stmia	r0!, {r3,r4,r5,r6, r7,r8,r9,r10}
+        mov	r3, r11, lsr #24
+        bhs	1b
+
+less_than_thirtytwo:
+	/* copy the last 0 to 31 bytes of the source */
+	rsb	r12, lr, #32		/* we corrupted r12, recompute it  */
+        add	r2, r2, #32
+        cmp	r2, #4
+        blo	partial_word_tail
+
+1:	ldr	r5, [r1], #4
+        sub    	r2, r2, #4
+        orr	r4, r3, r5,		lsl lr
+        mov	r3,	r5,			lsr r12
+        str	r4, [r0], #4
+        cmp    	r2, #4
+        bhs	1b
+
+partial_word_tail:
+	/* we have a partial word in the input buffer */
+	movs	r5, lr, lsl #(31-3)
+	strmib	r3, [r0], #1
+        movmi	r3, r3, lsr #8
+        strcsb	r3, [r0], #1
+        movcs	r3, r3, lsr #8
+        strcsb	r3, [r0], #1
+
+        /* Refill spilled registers from the stack. Don't update sp. */
+        ldmfd	sp, {r5-r11}
+
+copy_last_3_and_return:
+	movs	r2, r2, lsl #31	/* copy remaining 0, 1, 2 or 3 bytes */
+        ldrmib	r2, [r1], #1
+        ldrcsb	r3, [r1], #1
+        ldrcsb	r12,[r1]
+        strmib	r2, [r0], #1
+        strcsb	r3, [r0], #1
+        strcsb	r12,[r0]
+
+        /* we're done! restore sp and spilled registers and return */
+        add    	sp,  sp, #28
+        ldmfd	sp!, {r0, r4, lr}
+        bx	lr
+
-- 
1.7.9.5

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