[thirdparty/glibc.git] / sysdeps / generic / memcopy.h

/* memcopy.h -- definitions for memory copy functions.  Generic C version.
   Copyright (C) 1991-2019 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Torbjorn Granlund (tege@sics.se).

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#ifndef _MEMCOPY_H
#define _MEMCOPY_H	1

/* The strategy of the memory functions is:

     1. Copy bytes until the destination pointer is aligned.

     2. Copy words in unrolled loops.  If the source and destination
     are not aligned in the same way, use word memory operations,
     but shift and merge two read words before writing.

     3. Copy the few remaining bytes.

   This is fast on processors that have at least 10 registers for
   allocation by GCC, and that can access memory at reg+const in one
   instruction.

   I made an "exhaustive" test of this memmove when I wrote it,
   exhaustive in the sense that I tried all alignment and length
   combinations, with and without overlap.  */

#include <sys/cdefs.h>
#include <endian.h>
#include <pagecopy.h>

/* The macros defined in this file are:

   BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)

   BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)

   WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)

   WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)

   MERGE(old_word, sh_1, new_word, sh_2)
     [I fail to understand.  I feel stupid.  --roland]
*/

/* Type to use for aligned memory operations.
   This should normally be the biggest type supported by a single load
   and store.  */
#define	op_t	unsigned long int
#define OPSIZ	(sizeof (op_t))

/* Type to use for unaligned operations.  */
typedef unsigned char byte;

#if __BYTE_ORDER == __LITTLE_ENDIAN
#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) | ((w1) << (sh_2)))
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
#define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) | ((w1) >> (sh_2)))
#endif

/* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
   without any assumptions about alignment of the pointers.  */
#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes)				      \
  do									      \
    {									      \
      size_t __nbytes = (nbytes);					      \
      while (__nbytes > 0)						      \
	{								      \
	  byte __x = ((byte *) src_bp)[0];				      \
	  src_bp += 1;							      \
	  __nbytes -= 1;						      \
	  ((byte *) dst_bp)[0] = __x;					      \
	  dst_bp += 1;							      \
	}								      \
    } while (0)

/* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
   beginning at the bytes right before the pointers and continuing towards
   smaller addresses.  Don't assume anything about alignment of the
   pointers.  */
#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes)				      \
  do									      \
    {									      \
      size_t __nbytes = (nbytes);					      \
      while (__nbytes > 0)						      \
	{								      \
	  byte __x;							      \
	  src_ep -= 1;							      \
	  __x = ((byte *) src_ep)[0];					      \
	  dst_ep -= 1;							      \
	  __nbytes -= 1;						      \
	  ((byte *) dst_ep)[0] = __x;					      \
	}								      \
    } while (0)

/* Copy *up to* NBYTES bytes from SRC_BP to DST_BP, with
   the assumption that DST_BP is aligned on an OPSIZ multiple.  If
   not all bytes could be easily copied, store remaining number of bytes
   in NBYTES_LEFT, otherwise store 0.  */
extern void _wordcopy_fwd_aligned (long int, long int, size_t)
  attribute_hidden __THROW;
extern void _wordcopy_fwd_dest_aligned (long int, long int, size_t)
  attribute_hidden __THROW;
#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes)		      \
  do									      \
    {									      \
      if (src_bp % OPSIZ == 0)						      \
	_wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);	      \
      else								      \
	_wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ);	      \
      src_bp += (nbytes) & -OPSIZ;					      \
      dst_bp += (nbytes) & -OPSIZ;					      \
      (nbytes_left) = (nbytes) % OPSIZ;					      \
    } while (0)

/* Copy *up to* NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
   beginning at the words (of type op_t) right before the pointers and
   continuing towards smaller addresses.  May take advantage of that
   DST_END_PTR is aligned on an OPSIZ multiple.  If not all bytes could be
   easily copied, store remaining number of bytes in NBYTES_REMAINING,
   otherwise store 0.  */
extern void _wordcopy_bwd_aligned (long int, long int, size_t)
  attribute_hidden __THROW;
extern void _wordcopy_bwd_dest_aligned (long int, long int, size_t)
  attribute_hidden __THROW;
#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes)		      \
  do									      \
    {									      \
      if (src_ep % OPSIZ == 0)						      \
	_wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);	      \
      else								      \
	_wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ);	      \
      src_ep -= (nbytes) & -OPSIZ;					      \
      dst_ep -= (nbytes) & -OPSIZ;					      \
      (nbytes_left) = (nbytes) % OPSIZ;					      \
    } while (0)

/* The macro PAGE_COPY_FWD_MAYBE (dstp, srcp, nbytes_left, nbytes) is invoked
   like WORD_COPY_FWD et al.  The pointers should be at least word aligned.
   This will check if virtual copying by pages can and should be done and do it
   if so.  The pointers will be aligned to PAGE_SIZE bytes.  The macro requires
   that pagecopy.h defines at least PAGE_COPY_THRESHOLD to 0.  If
   PAGE_COPY_THRESHOLD is non-zero, the header must also define PAGE_COPY_FWD
   and PAGE_SIZE.
*/
#if PAGE_COPY_THRESHOLD

# include <assert.h>

# define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes)		      \
  do									      \
    {									      \
      if ((nbytes) >= PAGE_COPY_THRESHOLD				      \
	  && PAGE_OFFSET ((dstp) - (srcp)) == 0)			      \
	{								      \
	  /* The amount to copy is past the threshold for copying	      \
	     pages virtually with kernel VM operations, and the		      \
	     source and destination addresses have the same alignment.  */    \
	  size_t nbytes_before = PAGE_OFFSET (-(dstp));			      \
	  if (nbytes_before != 0)					      \
	    {								      \
	      /* First copy the words before the first page boundary.  */     \
	      WORD_COPY_FWD (dstp, srcp, nbytes_left, nbytes_before);	      \
	      assert (nbytes_left == 0);				      \
	      nbytes -= nbytes_before;					      \
	    }								      \
	  PAGE_COPY_FWD (dstp, srcp, nbytes_left, nbytes);		      \
	}								      \
    } while (0)

/* The page size is always a power of two, so we can avoid modulo division.  */
# define PAGE_OFFSET(n)	((n) & (PAGE_SIZE - 1))

#else

# define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes) /* nada */

#endif

/* Threshold value for when to enter the unrolled loops.  */
#define	OP_T_THRES	16

/* Set to 1 if memcpy is safe to use for forward-copying memmove with
   overlapping addresses.  This is 0 by default because memcpy implementations
   are generally not safe for overlapping addresses.  */
#define MEMCPY_OK_FOR_FWD_MEMMOVE 0

#endif /* memcopy.h */
Commit	Line	Data
28f540f4	1	/* memcopy.h -- definitions for memory copy functions. Generic C version.
04277e02	2	Copyright (C) 1991-2019 Free Software Foundation, Inc.
41bdb6e2	3	This file is part of the GNU C Library.
28f540f4 RM	4	Contributed by Torbjorn Granlund (tege@sics.se).
28f540f4 RM	5
c84142e8	6	The GNU C Library is free software; you can redistribute it and/or
41bdb6e2 AJ	7	modify it under the terms of the GNU Lesser General Public
	8	License as published by the Free Software Foundation; either
	9	version 2.1 of the License, or (at your option) any later version.
28f540f4	10
c84142e8 UD	11	The GNU C Library is distributed in the hope that it will be useful,
	12	but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
41bdb6e2	14	Lesser General Public License for more details.
28f540f4	15
41bdb6e2	16	You should have received a copy of the GNU Lesser General Public
59ba27a6	17	License along with the GNU C Library; if not, see
5a82c748	18	<https://www.gnu.org/licenses/>. */
28f540f4	19
c8df52ec DM	20	#ifndef _MEMCOPY_H
	21	#define _MEMCOPY_H 1
	22
28f540f4 RM	23	/* The strategy of the memory functions is:
	24
	25	1. Copy bytes until the destination pointer is aligned.
	26
	27	2. Copy words in unrolled loops. If the source and destination
	28	are not aligned in the same way, use word memory operations,
	29	but shift and merge two read words before writing.
	30
	31	3. Copy the few remaining bytes.
	32
	33	This is fast on processors that have at least 10 registers for
	34	allocation by GCC, and that can access memory at reg+const in one
	35	instruction.
	36
	37	I made an "exhaustive" test of this memmove when I wrote it,
	38	exhaustive in the sense that I tried all alignment and length
	39	combinations, with and without overlap. */
	40
	41	#include <sys/cdefs.h>
	42	#include <endian.h>
99f8dc92	43	#include <pagecopy.h>
28f540f4 RM	44
	45	/* The macros defined in this file are:
	46
	47	BYTE_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_to_copy)
	48
	49	BYTE_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_to_copy)
	50
	51	WORD_COPY_FWD(dst_beg_ptr, src_beg_ptr, nbytes_remaining, nbytes_to_copy)
	52
	53	WORD_COPY_BWD(dst_end_ptr, src_end_ptr, nbytes_remaining, nbytes_to_copy)
	54
	55	MERGE(old_word, sh_1, new_word, sh_2)
	56	[I fail to understand. I feel stupid. --roland]
	57	*/
	58
	59	/* Type to use for aligned memory operations.
	60	This should normally be the biggest type supported by a single load
	61	and store. */
	62	#define op_t unsigned long int
c4f50205	63	#define OPSIZ (sizeof (op_t))
28f540f4 RM	64
	65	/* Type to use for unaligned operations. */
	66	typedef unsigned char byte;
	67
28f540f4 RM	68	#if __BYTE_ORDER == __LITTLE_ENDIAN
	69	#define MERGE(w0, sh_1, w1, sh_2) (((w0) >> (sh_1)) \| ((w1) << (sh_2)))
	70	#endif
	71	#if __BYTE_ORDER == __BIG_ENDIAN
	72	#define MERGE(w0, sh_1, w1, sh_2) (((w0) << (sh_1)) \| ((w1) >> (sh_2)))
	73	#endif
	74
	75	/* Copy exactly NBYTES bytes from SRC_BP to DST_BP,
	76	without any assumptions about alignment of the pointers. */
	77	#define BYTE_COPY_FWD(dst_bp, src_bp, nbytes) \
	78	do \
	79	{ \
	80	size_t __nbytes = (nbytes); \
	81	while (__nbytes > 0) \
	82	{ \
	83	byte __x = ((byte *) src_bp)[0]; \
	84	src_bp += 1; \
	85	__nbytes -= 1; \
	86	((byte *) dst_bp)[0] = __x; \
	87	dst_bp += 1; \
	88	} \
	89	} while (0)
	90
	91	/* Copy exactly NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
	92	beginning at the bytes right before the pointers and continuing towards
	93	smaller addresses. Don't assume anything about alignment of the
	94	pointers. */
	95	#define BYTE_COPY_BWD(dst_ep, src_ep, nbytes) \
	96	do \
	97	{ \
	98	size_t __nbytes = (nbytes); \
	99	while (__nbytes > 0) \
	100	{ \
	101	byte __x; \
	102	src_ep -= 1; \
	103	__x = ((byte *) src_ep)[0]; \
	104	dst_ep -= 1; \
	105	__nbytes -= 1; \
	106	((byte *) dst_ep)[0] = __x; \
	107	} \
	108	} while (0)
	109
	110	/* Copy up to NBYTES bytes from SRC_BP to DST_BP, with
	111	the assumption that DST_BP is aligned on an OPSIZ multiple. If
	112	not all bytes could be easily copied, store remaining number of bytes
	113	in NBYTES_LEFT, otherwise store 0. */
b8b21bde L	114	extern void _wordcopy_fwd_aligned (long int, long int, size_t)
	115	attribute_hidden __THROW;
	116	extern void _wordcopy_fwd_dest_aligned (long int, long int, size_t)
	117	attribute_hidden __THROW;
28f540f4 RM	118	#define WORD_COPY_FWD(dst_bp, src_bp, nbytes_left, nbytes) \
	119	do \
	120	{ \
	121	if (src_bp % OPSIZ == 0) \
	122	_wordcopy_fwd_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \
	123	else \
	124	_wordcopy_fwd_dest_aligned (dst_bp, src_bp, (nbytes) / OPSIZ); \
	125	src_bp += (nbytes) & -OPSIZ; \
	126	dst_bp += (nbytes) & -OPSIZ; \
	127	(nbytes_left) = (nbytes) % OPSIZ; \
	128	} while (0)
	129
	130	/* Copy up to NBYTES_TO_COPY bytes from SRC_END_PTR to DST_END_PTR,
	131	beginning at the words (of type op_t) right before the pointers and
	132	continuing towards smaller addresses. May take advantage of that
	133	DST_END_PTR is aligned on an OPSIZ multiple. If not all bytes could be
	134	easily copied, store remaining number of bytes in NBYTES_REMAINING,
	135	otherwise store 0. */
b8b21bde L	136	extern void _wordcopy_bwd_aligned (long int, long int, size_t)
	137	attribute_hidden __THROW;
	138	extern void _wordcopy_bwd_dest_aligned (long int, long int, size_t)
	139	attribute_hidden __THROW;
28f540f4 RM	140	#define WORD_COPY_BWD(dst_ep, src_ep, nbytes_left, nbytes) \
	141	do \
	142	{ \
	143	if (src_ep % OPSIZ == 0) \
	144	_wordcopy_bwd_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \
	145	else \
	146	_wordcopy_bwd_dest_aligned (dst_ep, src_ep, (nbytes) / OPSIZ); \
	147	src_ep -= (nbytes) & -OPSIZ; \
	148	dst_ep -= (nbytes) & -OPSIZ; \
	149	(nbytes_left) = (nbytes) % OPSIZ; \
	150	} while (0)
	151
99f8dc92 SP	152	/* The macro PAGE_COPY_FWD_MAYBE (dstp, srcp, nbytes_left, nbytes) is invoked
	153	like WORD_COPY_FWD et al. The pointers should be at least word aligned.
	154	This will check if virtual copying by pages can and should be done and do it
	155	if so. The pointers will be aligned to PAGE_SIZE bytes. The macro requires
	156	that pagecopy.h defines at least PAGE_COPY_THRESHOLD to 0. If
	157	PAGE_COPY_THRESHOLD is non-zero, the header must also define PAGE_COPY_FWD
	158	and PAGE_SIZE.
	159	*/
	160	#if PAGE_COPY_THRESHOLD
	161
	162	# include <assert.h>
	163
	164	# define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes) \
	165	do \
	166	{ \
a04549c1 JM	167	if ((nbytes) >= PAGE_COPY_THRESHOLD \
a04549c1 JM	168	&& PAGE_OFFSET ((dstp) - (srcp)) == 0) \
99f8dc92 SP	169	{ \
	170	/* The amount to copy is past the threshold for copying \
	171	pages virtually with kernel VM operations, and the \
	172	source and destination addresses have the same alignment. */ \
	173	size_t nbytes_before = PAGE_OFFSET (-(dstp)); \
	174	if (nbytes_before != 0) \
	175	{ \
	176	/* First copy the words before the first page boundary. */ \
	177	WORD_COPY_FWD (dstp, srcp, nbytes_left, nbytes_before); \
	178	assert (nbytes_left == 0); \
	179	nbytes -= nbytes_before; \
	180	} \
	181	PAGE_COPY_FWD (dstp, srcp, nbytes_left, nbytes); \
	182	} \
	183	} while (0)
	184
	185	/* The page size is always a power of two, so we can avoid modulo division. */
	186	# define PAGE_OFFSET(n) ((n) & (PAGE_SIZE - 1))
	187
	188	#else
	189
	190	# define PAGE_COPY_FWD_MAYBE(dstp, srcp, nbytes_left, nbytes) /* nada */
	191
	192	#endif
28f540f4 RM	193
	194	/* Threshold value for when to enter the unrolled loops. */
	195	#define OP_T_THRES 16
c8df52ec	196
96baf6ff SP	197	/* Set to 1 if memcpy is safe to use for forward-copying memmove with
	198	overlapping addresses. This is 0 by default because memcpy implementations
	199	are generally not safe for overlapping addresses. */
64df73c2 SP	200	#define MEMCPY_OK_FOR_FWD_MEMMOVE 0
64df73c2 SP	201
c8df52ec	202	#endif /* memcopy.h */