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Store less-than-word-sized values in LSBs of box.

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runtime/mercury_heap.h:
    Store less-than-word-sized values in least significant bits of a
    box. This makes no difference on little endian machines.
    On big endian machines, it affects the value printed out
    when the box is printed generically.
This commit is contained in:
Peter Wang
2019-06-08 16:40:24 +10:00
parent dfab1619c2
commit 2e9b41d8a2
1 changed files with 30 additions and 24 deletions
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54
runtime/mercury_heap.h
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@@ -480,14 +480,21 @@
// Copy a value of type T from `value' to `box', boxing it if necessary
// (i.e. if type T won't fit in type MR_Box).
#ifdef MR_BIG_ENDIAN
#define MR_IF_BIG_ENDIAN(x) do { x } while (0)
#else
#define MR_IF_BIG_ENDIAN(x) do { } while (0)
#endif
#define MR_MAYBE_BOX_FOREIGN_TYPE(T, value, box) \
do { \
MR_CHECK_EXPR_TYPE((value), T); \
MR_CHECK_EXPR_TYPE((box), MR_Box); \
if (sizeof(T) == sizeof(MR_Box)) { \
long extra_bytes = (long) sizeof(T) - (long) sizeof(MR_Box); \
if (extra_bytes == 0L) { \
(box) = * (MR_Box *) &(value); \
} else if (sizeof(T) > sizeof(MR_Box)) { \
MR_Word box_word; \
} else if (extra_bytes > 0L) { \
MR_Word box_word; \
size_t size_in_words = \
(sizeof(T) + sizeof(MR_Word) - 1) / sizeof(MR_Word); \
/* \
@@ -506,19 +513,14 @@
MR_profmem_record_allocation(size_in_words, NULL, \
"foreign type: " MR_STRINGIFY(T)); \
} else { \
/* \
** We can't take the address of `box' here, \
** since it might be a global register. \
** Hence we need to use a temporary copy. \
*/ \
MR_Box box_copy; \
if (sizeof(T) < sizeof(MR_Box)) { \
/* \
** Make sure we don't leave any part of it uninitialized. \
*/ \
box_copy = 0; \
} \
MR_Box box_copy = 0; \
MR_memcpy(&box_copy, &(value), sizeof(T)); \
/* Store value in least significant bits. */ \
MR_IF_BIG_ENDIAN( \
MR_Word box_word = (MR_Word) box_copy; \
box_word >>= -(extra_bytes * CHAR_BIT); \
box_copy = (MR_Box) box_word; \
); \
(box) = box_copy; \
} \
} while (0)
@@ -530,20 +532,24 @@
do { \
MR_CHECK_EXPR_TYPE((value), T); \
MR_CHECK_EXPR_TYPE((box), MR_Box); \
if (sizeof(T) > sizeof(MR_Word)) { \
MR_assign_structure((value), * (T *) (box)); \
} else { \
long extra_bytes = (long) sizeof(T) - (long) sizeof(MR_Box); \
if (extra_bytes == 0L) { \
/* \
** We can't take the address of `box' here, \
** since it might be a global register. \
** Hence we need to use a temporary copy. \
*/ \
MR_Box box_copy = (box); \
if (sizeof(T) == sizeof(MR_Box)) { \
(value) = * (T *) &box_copy; \
} else { \
MR_memcpy(&(value), &box_copy, sizeof(T)); \
} \
(value) = * (T *) &box_copy; \
} else if (extra_bytes > 0L) { \
MR_assign_structure((value), * (T *) (box)); \
} else { \
MR_Box box_copy = (box); \
MR_IF_BIG_ENDIAN( \
MR_Word box_word = (MR_Word) box_copy; \
box_word <<= -(extra_bytes * CHAR_BIT); \
box_copy = (MR_Box) box_word; \
); \
MR_memcpy(&(value), &box_copy, sizeof(T)); \
} \
} while (0)