/* scan.c: SCANNING FUNCTIONS * * $Id$ * Copyright (c) 2001-2016 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. 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