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/* scan.c: SCANNING FUNCTIONS
*
* $Id$
* Copyright (c) 2001-2020 Ravenbrook Limited.
* See end of file for license.
*
* .outside: The code in this file is written as if *outside* the MPS,
* and so is restricted to facilities in the MPS interface. MPS users
* are invited to read this code and use it as a basis for their own
* scanners. See topic "Area Scanners" in the MPS manual.
*
* TODO: Design document.
*/
#include "mps.h"
#include "mpstd.h" /* for MPS_BUILD_MV */
#ifdef MPS_BUILD_MV
/* MSVC warning 4127 = conditional expression is constant */
/* Objects to: MPS_SCAN_AREA(1). */
#pragma warning( disable : 4127 )
#endif
#define MPS_SCAN_AREA(test) \
MPS_SCAN_BEGIN(ss) { \
mps_word_t *p = base; \
while (p < (mps_word_t *)limit) { \
mps_word_t word = *p; \
mps_word_t tag_bits = word & mask; \
if (test) { \
mps_addr_t ref = (mps_addr_t)(word ^ tag_bits); \
if (MPS_FIX1(ss, ref)) { \
mps_res_t res = MPS_FIX2(ss, &ref); \
if (res != MPS_RES_OK) \
return res; \
*p = (mps_word_t)ref | tag_bits; \
} \
} \
++p; \
} \
} MPS_SCAN_END(ss);
/* mps_scan_area -- scan contiguous area of references
*
* This is a convenience function for scanning the contiguous area
* [base, limit). I.e., it calls Fix on all words from base up to
* limit, inclusive of base and exclusive of limit.
*
* This scanner is appropriate for use when all words in the area are
* simple untagged references.
*/
mps_res_t mps_scan_area(mps_ss_t ss,
void *base, void *limit,
void *closure)
{
mps_word_t mask = 0;
(void)closure; /* unused */
MPS_SCAN_AREA(1);
return MPS_RES_OK;
}
/* mps_scan_area_masked -- scan area masking off tag bits
*
* Like mps_scan_area, but removes tag bits before fixing references,
* and restores them afterwards.
*
* For example, if mask is 7, then this scanner will clear the bottom
* three bits of each word before fixing.
*
* This scanner is useful when all words in the area must be treated
* as references no matter what tag they have.
*/
mps_res_t mps_scan_area_masked(mps_ss_t ss,
void *base, void *limit,
void *closure)
{
mps_scan_tag_t tag = closure;
mps_word_t mask = tag->mask;
MPS_SCAN_AREA(1);
return MPS_RES_OK;
}
/* mps_scan_area_tagged -- scan area selecting by tag
*
* Like mps_scan_area_masked, except only references whose masked bits
* match a particular tag pattern are fixed.
*
* For example, if mask is 7 and pattern is 5, then this scanner will
* only fix words whose low order bits are 0b101.
*/
mps_res_t mps_scan_area_tagged(mps_ss_t ss,
void *base, void *limit,
void *closure)
{
mps_scan_tag_t tag = closure;
mps_word_t mask = tag->mask;
mps_word_t pattern = tag->pattern;
MPS_SCAN_AREA(tag_bits == pattern);
return MPS_RES_OK;
}
/* mps_scan_area_tagged_or_zero -- scan area selecting by tag or zero
*
* Like mps_scan_area_tagged, except references whose masked bits are
* zero are fixed in addition to those that match the pattern.
*
* For example, if mask is 7 and pattern is 3, then this scanner will
* fix words whose low order bits are 0b011 and words whose low order
* bits are 0b000, but not any others.
*
* This scanner is most useful for ambiguously scanning the stack and
* registers when using an optimising C compiler and non-zero tags on
* references, since the compiler is likely to leave untagged
* addresses of objects around which must not be ignored.
*/
mps_res_t mps_scan_area_tagged_or_zero(mps_ss_t ss,
void *base, void *limit,
void *closure)
{
mps_scan_tag_t tag = closure;
mps_word_t mask = tag->mask;
mps_word_t pattern = tag->pattern;
MPS_SCAN_AREA(tag_bits == 0 || tag_bits == pattern);
return MPS_RES_OK;
}
/* C. COPYRIGHT AND LICENSE
*
* Copyright (C) 2001-2020 Ravenbrook Limited <https://www.ravenbrook.com/>.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. 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
* HOLDER 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.
*/
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