runtime/mercury_heap.h:
Store less-than-word-sized values in least significant bits of a
box. This makes no any difference on little endian machines.
On big endian machines, affects the value printed out
when the box is printed generically.
diff --git a/runtime/mercury_heap.h b/runtime/mercury_heap.h
index 6837af28f..7cd437326 100644
--- a/runtime/mercury_heap.h
+++ b/runtime/mercury_heap.h
@@ -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)
--
2.21.0