checksum.s

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/* checksum.S: Sparc optimized checksum code.
 *
 *  Copyright(C) 1995 Linus Torvalds
 *  Copyright(C) 1995 Miguel de Icaza
 *  Copyright(C) 1996 David S. Miller
 *  Copyright(C) 1997 Jakub Jelinek
 *
 * derived from:
 *	Linux/Alpha checksum c-code
 *      Linux/ix86 inline checksum assembly
 *      RFC1071 Computing the Internet Checksum (esp. Jacobsons m68k code)
 *	David Mosberger-Tang for optimized reference c-code
 *	BSD4.4 portable checksum routine
 */

#include <asm/cprefix.h>
#include <asm/errno.h>

#define CSUM_BIGCHUNK(buf, offset, sum, t0, t1, t2, t3, t4, t5)	\
	ldd	[buf + offset + 0x00], t0;			\
	ldd	[buf + offset + 0x08], t2;			\
	addxcc	t0, sum, sum;					\
	addxcc	t1, sum, sum;					\
	ldd	[buf + offset + 0x10], t4;			\
	addxcc	t2, sum, sum;					\
	addxcc	t3, sum, sum;					\
	ldd	[buf + offset + 0x18], t0;			\
	addxcc	t4, sum, sum;					\
	addxcc	t5, sum, sum;					\
	addxcc	t0, sum, sum;					\
	addxcc	t1, sum, sum;

#define CSUM_LASTCHUNK(buf, offset, sum, t0, t1, t2, t3)	\
	ldd	[buf - offset - 0x08], t0;			\
	ldd	[buf - offset - 0x00], t2;			\
	addxcc	t0, sum, sum;					\
	addxcc	t1, sum, sum;					\
	addxcc	t2, sum, sum;					\
	addxcc	t3, sum, sum;

	/* Do end cruft out of band to get better cache patterns. */
csum_partial_end_cruft:
	be	1f				! caller asks %o1 & 0x8
	 andcc	%o1, 4, %g0			! nope, check for word remaining
	ldd	[%o0], %g2			! load two
	addcc	%g2, %o2, %o2			! add first word to sum
	addxcc	%g3, %o2, %o2			! add second word as well
	add	%o0, 8, %o0			! advance buf ptr
	addx	%g0, %o2, %o2			! add in final carry
	andcc	%o1, 4, %g0			! check again for word remaining
1:	be	1f				! nope, skip this code
	 andcc	%o1, 3, %o1			! check for trailing bytes
	ld	[%o0], %g2			! load it
	addcc	%g2, %o2, %o2			! add to sum
	add	%o0, 4, %o0			! advance buf ptr
	addx	%g0, %o2, %o2			! add in final carry
	andcc	%o1, 3, %g0			! check again for trailing bytes
1:	be	1f				! no trailing bytes, return
	 addcc	%o1, -1, %g0			! only one byte remains?
	bne	2f				! at least two bytes more
	 subcc	%o1, 2, %o1			! only two bytes more?
	b	4f				! only one byte remains
	 or	%g0, %g0, %o4			! clear fake hword value
2:	lduh	[%o0], %o4			! get hword
	be	6f				! jmp if only hword remains
	 add	%o0, 2, %o0			! advance buf ptr either way
	sll	%o4, 16, %o4			! create upper hword
4:	ldub	[%o0], %o5			! get final byte
	sll	%o5, 8, %o5			! put into place
	or	%o5, %o4, %o4			! coalese with hword (if any)
6:	addcc	%o4, %o2, %o2			! add to sum
1:	retl					! get outta here
	 addx	%g0, %o2, %o0			! add final carry into retval

	/* Also do alignment out of band to get better cache patterns. */
csum_partial_fix_alignment:
	cmp	%o1, 6
	bl	cpte - 0x4
	 andcc	%o0, 0x2, %g0
	be	1f
	 andcc	%o0, 0x4, %g0
	lduh	[%o0 + 0x00], %g2
	sub	%o1, 2, %o1
	add	%o0, 2, %o0
	sll	%g2, 16, %g2
	addcc	%g2, %o2, %o2
	srl	%o2, 16, %g3
	addx	%g0, %g3, %g2
	sll	%o2, 16, %o2
	sll	%g2, 16, %g3
	srl	%o2, 16, %o2
	andcc	%o0, 0x4, %g0
	or	%g3, %o2, %o2
1:	be	cpa
	 andcc	%o1, 0xffffff80, %o3
	ld	[%o0 + 0x00], %g2
	sub	%o1, 4, %o1
	addcc	%g2, %o2, %o2
	add	%o0, 4, %o0
	addx	%g0, %o2, %o2
	b	cpa
	 andcc	%o1, 0xffffff80, %o3

	/* The common case is to get called with a nicely aligned
	 * buffer of size 0x20.  Follow the code path for that case.
	 */
	.globl	C_LABEL(csum_partial)
C_LABEL(csum_partial):			/* %o0=buf, %o1=len, %o2=sum */
	andcc	%o0, 0x7, %g0				! alignment problems?
	bne	csum_partial_fix_alignment		! yep, handle it
	 sethi	%hi(cpte - 8), %g7			! prepare table jmp ptr
	andcc	%o1, 0xffffff80, %o3			! num loop iterations
cpa:	be	3f					! none to do
	 andcc	%o1, 0x70, %g1				! clears carry flag too
5:	CSUM_BIGCHUNK(%o0, 0x00, %o2, %o4, %o5, %g2, %g3, %g4, %g5)
	CSUM_BIGCHUNK(%o0, 0x20, %o2, %o4, %o5, %g2, %g3, %g4, %g5)
	CSUM_BIGCHUNK(%o0, 0x40, %o2, %o4, %o5, %g2, %g3, %g4, %g5)
	CSUM_BIGCHUNK(%o0, 0x60, %o2, %o4, %o5, %g2, %g3, %g4, %g5)
	addx	%g0, %o2, %o2				! sink in final carry
	subcc	%o3, 128, %o3				! detract from loop iters
	bne	5b					! more to do
	 add	%o0, 128, %o0				! advance buf ptr
	andcc	%o1, 0x70, %g1				! clears carry flag too
3:	be	cpte					! nope
	 andcc	%o1, 0xf, %g0				! anything left at all?
	srl	%g1, 1, %o4				! compute offset
	sub	%g7, %g1, %g7				! adjust jmp ptr
	sub	%g7, %o4, %g7				! final jmp ptr adjust
	jmp	%g7 + %lo(cpte - 8)			! enter the table
	 add	%o0, %g1, %o0				! advance buf ptr
cptbl:	CSUM_LASTCHUNK(%o0, 0x68, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x58, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x48, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x38, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x28, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x18, %o2, %g2, %g3, %g4, %g5)
	CSUM_LASTCHUNK(%o0, 0x08, %o2, %g2, %g3, %g4, %g5)
	addx	%g0, %o2, %o2				! fetch final carry
	andcc	%o1, 0xf, %g0				! anything left at all?
cpte:	bne	csum_partial_end_cruft			! yep, handle it
	 andcc	%o1, 8, %g0				! check how much
cpout:	retl						! get outta here
	 mov	%o2, %o0				! return computed csum

	.globl C_LABEL(__csum_partial_copy_start), C_LABEL(__csum_partial_copy_end)
C_LABEL(__csum_partial_copy_start):

#define EX(x,y,a,b,z)                           \
98:     x,y;                                    \
        .section .fixup,z##alloc,z##execinstr;  \
        .align  4;                              \
99:     ba 30f;                                 \
         a, b, %o3;                             \
        .section __ex_table,z##alloc;           \
        .align  4;                              \
        .word   98b, 99b;                       \
        .text;                                  \
        .align  4

#define EX2(x,y,z)                          	\
98:     x,y;                                    \
        .section __ex_table,z##alloc;           \
        .align  4;                              \
        .word   98b, 30f;                       \
        .text;                                  \
        .align  4

#define EX3(x,y,z)                          	\
98:     x,y;                                    \
        .section __ex_table,z##alloc;           \
        .align  4;                              \
        .word   98b, 96f;                       \
        .text;                                  \
        .align  4

#define EXT(start,end,handler,z)                \
        .section __ex_table,z##alloc;           \
        .align  4;                              \
        .word   start, 0, end, handler;         \
        .text;                                  \
        .align  4

	/* This aligned version executes typically in 8.5 superscalar cycles, this
	 * is the best I can do.  I say 8.5 because the final add will pair with
	 * the next ldd in the main unrolled loop.  Thus the pipe is always full.
	 * If you change these macros (including order of instructions),
	 * please check the fixup code below as well.
	 */
#define CSUMCOPY_BIGCHUNK_ALIGNED(src, dst, sum, off, t0, t1, t2, t3, t4, t5, t6, t7)	\
	ldd	[src + off + 0x00], t0;							\
	ldd	[src + off + 0x08], t2;							\
	addxcc	t0, sum, sum;								\
	ldd	[src + off + 0x10], t4;							\
	addxcc	t1, sum, sum;								\
	ldd	[src + off + 0x18], t6;							\
	addxcc	t2, sum, sum;								\
	std	t0, [dst + off + 0x00];							\
	addxcc	t3, sum, sum;								\
	std	t2, [dst + off + 0x08];							\
	addxcc	t4, sum, sum;								\
	std	t4, [dst + off + 0x10];							\
	addxcc	t5, sum, sum;								\
	std	t6, [dst + off + 0x18];							\
	addxcc	t6, sum, sum;								\
	addxcc	t7, sum, sum;

	/* 12 superscalar cycles seems to be the limit for this case,
	 * because of this we thus do all the ldd's together to get
	 * Viking MXCC into streaming mode.  Ho hum...
	 */
#define CSUMCOPY_BIGCHUNK(src, dst, sum, off, t0, t1, t2, t3, t4, t5, t6, t7)	\
	ldd	[src + off + 0x00], t0;						\
	ldd	[src + off + 0x08], t2;						\
	ldd	[src + off + 0x10], t4;						\
	ldd	[src + off + 0x18], t6;						\
	st	t0, [dst + off + 0x00];						\
	addxcc	t0, sum, sum;							\
	st	t1, [dst + off + 0x04];						\
	addxcc	t1, sum, sum;							\
	st	t2, [dst + off + 0x08];						\
	addxcc	t2, sum, sum;							\
	st	t3, [dst + off + 0x0c];						\
	addxcc	t3, sum, sum;							\
	st	t4, [dst + off + 0x10];						\
	addxcc	t4, sum, sum;							\
	st	t5, [dst + off + 0x14];						\
	addxcc	t5, sum, sum;							\
	st	t6, [dst + off + 0x18];						\
	addxcc	t6, sum, sum;							\
	st	t7, [dst + off + 0x1c];						\
	addxcc	t7, sum, sum;

	/* Yuck, 6 superscalar cycles... */
#define CSUMCOPY_LASTCHUNK(src, dst, sum, off, t0, t1, t2, t3)	\
	ldd	[src - off - 0x08], t0;				\
	ldd	[src - off - 0x00], t2;				\
	addxcc	t0, sum, sum;					\
	st	t0, [dst - off - 0x08];				\
	addxcc	t1, sum, sum;					\
	st	t1, [dst - off - 0x04];				\
	addxcc	t2, sum, sum;					\
	st	t2, [dst - off - 0x00];				\
	addxcc	t3, sum, sum;					\
	st	t3, [dst - off + 0x04];

	/* Handle the end cruft code out of band for better cache patterns. */
cc_end_cruft:
	be	1f
	 andcc	%o3, 4, %g0
	EX(ldd	[%o0 + 0x00], %g2, and %o3, 0xf,#)
	add	%o1, 8, %o1
	addcc	%g2, %g7, %g7
	add	%o0, 8, %o0
	addxcc	%g3, %g7, %g7
	EX2(st	%g2, [%o1 - 0x08],#)
	addx	%g0, %g7, %g7
	andcc	%o3, 4, %g0
	EX2(st	%g3, [%o1 - 0x04],#)
1:	be	1f
	 andcc	%o3, 3, %o3
	EX(ld	[%o0 + 0x00], %g2, add %o3, 4,#)
	add	%o1, 4, %o1
	addcc	%g2, %g7, %g7
	EX2(st	%g2, [%o1 - 0x04],#)
	addx	%g0, %g7, %g7
	andcc	%o3, 3, %g0
	add	%o0, 4, %o0
1:	be	1f
	 addcc	%o3, -1, %g0
	bne	2f
	 subcc	%o3, 2, %o3
	b	4f
	 or	%g0, %g0, %o4
2:	EX(lduh	[%o0 + 0x00], %o4, add %o3, 2,#)
	add	%o0, 2, %o0
	EX2(sth	%o4, [%o1 + 0x00],#)
	be	6f
	 add	%o1, 2, %o1
	sll	%o4, 16, %o4
4:	EX(ldub	[%o0 + 0x00], %o5, add %g0, 1,#)
	EX2(stb	%o5, [%o1 + 0x00],#)
	sll	%o5, 8, %o5
	or	%o5, %o4, %o4
6:	addcc	%o4, %g7, %g7
1:	retl
	 addx	%g0, %g7, %o0

	/* Also, handle the alignment code out of band. */
cc_dword_align:
	cmp	%g1, 6
	bl,a	ccte