memcpy_mck.s

linux-2.6.15.6

	;;
	add	r29=.jump_table - 1b - (.jmp1-.jump_table), r29
	shl	r28=r30, LOOP_SIZE	// jmp_table thread
	mov	ar.ec=2		// loop setup
	;;
	add	r29=r29,r28		// jmp_table thread
	cmp.eq	p16,p17=r0,r0
	;;
	mov	b6=r29			// jmp_table thread
	;;
	br.cond.sptk.few b6

// for 8-15 byte case
// We will skip the loop, but need to replicate the side effect
// that the loop produces.
.noloop:
EX(.ex_handler, (p6)	ld8	r37=[src1],8)
	add	src0=8,src0
(p6)	shl	r25=r30,3
	;;
EX(.ex_handler, (p6)	ld8	r27=[src1])
(p6)	shr.u	r28=r37,r25
(p6)	sub	r26=64,r25
	;;
(p6)	shl	r27=r27,r26
	;;
(p6)	or	r21=r28,r27

.unaligned_src_tail:
/* check if we have more than blocksize to copy, if so go back */
	cmp.gt	p8,p0=saved_in2,blocksize
	;;
(p8)	add	dst0=saved_in0,blocksize
(p8)	add	src0=saved_in1,blocksize
(p8)	sub	in2=saved_in2,blocksize
(p8)	br.dpnt	.4k_block
	;;

/* we have up to 15 byte to copy in the tail.
 * part of work is already done in the jump table code
 * we are at the following state.
 * src side:
 * 
 *   xxxxxx xx                   <----- r21 has xxxxxxxx already
 * -------- -------- --------
 * 0        8        16
 *          ^
 *          |
 *          src1
 * 
 * dst
 * -------- -------- --------
 * ^
 * |
 * dst1
 */
EX(.ex_handler, (p6)	st8	[dst1]=r21,8)	// more than 8 byte to copy
(p6)	add	curlen=-8,curlen	// update length
	mov	ar.pfs=saved_pfs
	;;
	mov	ar.lc=saved_lc
	mov	pr=saved_pr,-1
	mov	in2=curlen	// remaining length
	mov	dst0=dst1	// dest pointer
	add	src0=src1,r30	// forward by src alignment
	;;

// 7 byte or smaller.
.memcpy_short:
	cmp.le	p8,p9   = 1,in2
	cmp.le	p10,p11 = 2,in2
	cmp.le	p12,p13 = 3,in2
	cmp.le	p14,p15 = 4,in2
	add	src1=1,src0	// second src pointer
	add	dst1=1,dst0	// second dest pointer
	;;

EX(.ex_handler_short, (p8)	ld1	t1=[src0],2)
EK(.ex_handler_short, (p10)	ld1	t2=[src1],2)
(p9)	br.ret.dpnt rp		// 0 byte copy
	;;

EX(.ex_handler_short, (p8)	st1	[dst0]=t1,2)
EK(.ex_handler_short, (p10)	st1	[dst1]=t2,2)
(p11)	br.ret.dpnt rp		// 1 byte copy

EX(.ex_handler_short, (p12)	ld1	t3=[src0],2)
EK(.ex_handler_short, (p14)	ld1	t4=[src1],2)
(p13)	br.ret.dpnt rp		// 2 byte copy
	;;

	cmp.le	p6,p7   = 5,in2
	cmp.le	p8,p9   = 6,in2
	cmp.le	p10,p11 = 7,in2

EX(.ex_handler_short, (p12)	st1	[dst0]=t3,2)
EK(.ex_handler_short, (p14)	st1	[dst1]=t4,2)
(p15)	br.ret.dpnt rp		// 3 byte copy
	;;

EX(.ex_handler_short, (p6)	ld1	t5=[src0],2)
EK(.ex_handler_short, (p8)	ld1	t6=[src1],2)
(p7)	br.ret.dpnt rp		// 4 byte copy
	;;

EX(.ex_handler_short, (p6)	st1	[dst0]=t5,2)
EK(.ex_handler_short, (p8)	st1	[dst1]=t6,2)
(p9)	br.ret.dptk rp		// 5 byte copy

EX(.ex_handler_short, (p10)	ld1	t7=[src0],2)
(p11)	br.ret.dptk rp		// 6 byte copy
	;;

EX(.ex_handler_short, (p10)	st1	[dst0]=t7,2)
	br.ret.dptk rp		// done all cases


/* Align dest to nearest 8-byte boundary. We know we have at
 * least 7 bytes to copy, enough to crawl to 8-byte boundary.
 * Actual number of byte to crawl depend on the dest alignment.
 * 7 byte or less is taken care at .memcpy_short

 * src0 - source even index
 * src1 - source  odd index
 * dst0 - dest even index
 * dst1 - dest  odd index
 * r30  - distance to 8-byte boundary
 */

.align_dest:
	add	src1=1,in1	// source odd index
	cmp.le	p7,p0 = 2,r30	// for .align_dest
	cmp.le	p8,p0 = 3,r30	// for .align_dest
EX(.ex_handler_short, (p6)	ld1	t1=[src0],2)
	cmp.le	p9,p0 = 4,r30	// for .align_dest
	cmp.le	p10,p0 = 5,r30
	;;
EX(.ex_handler_short, (p7)	ld1	t2=[src1],2)
EK(.ex_handler_short, (p8)	ld1	t3=[src0],2)
	cmp.le	p11,p0 = 6,r30
EX(.ex_handler_short, (p6)	st1	[dst0] = t1,2)
	cmp.le	p12,p0 = 7,r30
	;;
EX(.ex_handler_short, (p9)	ld1	t4=[src1],2)
EK(.ex_handler_short, (p10)	ld1	t5=[src0],2)
EX(.ex_handler_short, (p7)	st1	[dst1] = t2,2)
EK(.ex_handler_short, (p8)	st1	[dst0] = t3,2)
	;;
EX(.ex_handler_short, (p11)	ld1	t6=[src1],2)
EK(.ex_handler_short, (p12)	ld1	t7=[src0],2)
	cmp.eq	p6,p7=r28,r29
EX(.ex_handler_short, (p9)	st1	[dst1] = t4,2)
EK(.ex_handler_short, (p10)	st1	[dst0] = t5,2)
	sub	in2=in2,r30
	;;
EX(.ex_handler_short, (p11)	st1	[dst1] = t6,2)
EK(.ex_handler_short, (p12)	st1	[dst0] = t7)
	add	dst0=in0,r30	// setup arguments
	add	src0=in1,r30
(p6)	br.cond.dptk .aligned_src
(p7)	br.cond.dpnt .unaligned_src
	;;

/* main loop body in jump table format */
#define COPYU(shift)									\
1:											\
EX(.ex_handler,  (p16)	ld8	r32=[src0],8);		/* 1 */				\
EK(.ex_handler,  (p16)	ld8	r36=[src1],8);						\
		 (p17)	shrp	r35=r33,r34,shift;;	/* 1 */				\
EX(.ex_handler,  (p6)	ld8	r22=[src1]);	/* common, prime for tail section */	\
		 nop.m	0;								\
		 (p16)	shrp	r38=r36,r37,shift;					\
EX(.ex_handler,  (p17)	st8	[dst0]=r35,8);		/* 1 */				\
EK(.ex_handler,  (p17)	st8	[dst1]=r39,8);						\
		 br.ctop.dptk.few 1b;;							\
		 (p7)	add	src1=-8,src1;	/* back out for <8 byte case */		\
		 shrp	r21=r22,r38,shift;	/* speculative work */			\
		 br.sptk.few .unaligned_src_tail /* branch out of jump table */		\
		 ;;
	TEXT_ALIGN(32)
.jump_table:
	COPYU(8)	// unaligned cases
.jmp1:
	COPYU(16)
	COPYU(24)
	COPYU(32)
	COPYU(40)
	COPYU(48)
	COPYU(56)

#undef A
#undef B
#undef C
#undef D

/*
 * Due to lack of local tag support in gcc 2.x assembler, it is not clear which
 * instruction failed in the bundle.  The exception algorithm is that we
 * first figure out the faulting address, then detect if there is any
 * progress made on the copy, if so, redo the copy from last known copied
 * location up to the faulting address (exclusive). In the copy_from_user
 * case, remaining byte in kernel buffer will be zeroed.
 *
 * Take copy_from_user as an example, in the code there are multiple loads
 * in a bundle and those multiple loads could span over two pages, the
 * faulting address is calculated as page_round_down(max(src0, src1)).
 * This is based on knowledge that if we can access one byte in a page, we
 * can access any byte in that page.
 *
 * predicate used in the exception handler:
 * p6-p7: direction
 * p10-p11: src faulting addr calculation
 * p12-p13: dst faulting addr calculation
 */

#define A	r19
#define B	r20
#define C	r21
#define D	r22
#define F	r28

#define memset_arg0	r32
#define memset_arg2	r33

#define saved_retval	loc0
#define saved_rtlink	loc1
#define saved_pfs_stack	loc2

.ex_hndlr_s:
	add	src0=8,src0
	br.sptk .ex_handler
	;;
.ex_hndlr_d:
	add	dst0=8,dst0
	br.sptk .ex_handler
	;;
.ex_hndlr_lcpy_1:
	mov	src1=src_pre_mem
	mov	dst1=dst_pre_mem
	cmp.gtu	p10,p11=src_pre_mem,saved_in1
	cmp.gtu	p12,p13=dst_pre_mem,saved_in0
	;;
(p10)	add	src0=8,saved_in1
(p11)	mov	src0=saved_in1
(p12)	add	dst0=8,saved_in0
(p13)	mov	dst0=saved_in0
	br.sptk	.ex_handler
.ex_handler_lcpy:
	// in line_copy block, the preload addresses should always ahead
	// of the other two src/dst pointers.  Furthermore, src1/dst1 should
	// always ahead of src0/dst0.
	mov	src1=src_pre_mem
	mov	dst1=dst_pre_mem
.ex_handler:
	mov	pr=saved_pr,-1		// first restore pr, lc, and pfs
	mov	ar.lc=saved_lc
	mov	ar.pfs=saved_pfs
	;;
.ex_handler_short: // fault occurred in these sections didn't change pr, lc, pfs
	cmp.ltu	p6,p7=saved_in0, saved_in1	// get the copy direction
	cmp.ltu	p10,p11=src0,src1
	cmp.ltu	p12,p13=dst0,dst1
	fcmp.eq	p8,p0=f6,f0		// is it memcpy?
	mov	tmp = dst0
	;;
(p11)	mov	src1 = src0		// pick the larger of the two
(p13)	mov	dst0 = dst1		// make dst0 the smaller one
(p13)	mov	dst1 = tmp		// and dst1 the larger one
	;;
(p6)	dep	F = r0,dst1,0,PAGE_SHIFT // usr dst round down to page boundary
(p7)	dep	F = r0,src1,0,PAGE_SHIFT // usr src round down to page boundary
	;;
(p6)	cmp.le	p14,p0=dst0,saved_in0	// no progress has been made on store
(p7)	cmp.le	p14,p0=src0,saved_in1	// no progress has been made on load
	mov	retval=saved_in2
(p8)	ld1	tmp=[src1]		// force an oops for memcpy call
(p8)	st1	[dst1]=r0		// force an oops for memcpy call
(p14)	br.ret.sptk.many rp

/*
 * The remaining byte to copy is calculated as:
 *
 * A =	(faulting_addr - orig_src)	-> len to faulting ld address
 *	or 
 * 	(faulting_addr - orig_dst)	-> len to faulting st address
 * B =	(cur_dst - orig_dst)		-> len copied so far
 * C =	A - B				-> len need to be copied
 * D =	orig_len - A			-> len need to be zeroed
 */
(p6)	sub	A = F, saved_in0
(p7)	sub	A = F, saved_in1
	clrrrb
	;;
	alloc	saved_pfs_stack=ar.pfs,3,3,3,0
	cmp.lt	p8,p0=A,r0
	sub	B = dst0, saved_in0	// how many byte copied so far
	;;
(p8)	mov	A = 0;			// A shouldn't be negative, cap it
	;;
	sub	C = A, B
	sub	D = saved_in2, A
	;;
	cmp.gt	p8,p0=C,r0		// more than 1 byte?
	add	memset_arg0=saved_in0, A
(p6)	mov	memset_arg2=0		// copy_to_user should not call memset
(p7)	mov	memset_arg2=D		// copy_from_user need to have kbuf zeroed
	mov	r8=0
	mov	saved_retval = D
	mov	saved_rtlink = b0

	add	out0=saved_in0, B
	add	out1=saved_in1, B
	mov	out2=C
(p8)	br.call.sptk.few b0=__copy_user	// recursive call
	;;

	add	saved_retval=saved_retval,r8	// above might return non-zero value
	cmp.gt	p8,p0=memset_arg2,r0	// more than 1 byte?
	mov	out0=memset_arg0	// *s
	mov	out1=r0			// c
	mov	out2=memset_arg2	// n
(p8)	br.call.sptk.few b0=memset
	;;

	mov	retval=saved_retval
	mov	ar.pfs=saved_pfs_stack
	mov	b0=saved_rtlink
	br.ret.sptk.many rp

/* end of McKinley specific optimization */
END(__copy_user)