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Changed multiply back to the very simplest implementation

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This commit is contained in:
Neil Brown 2009-01-23 13:36:09 +00:00
parent ecf840fe9f
commit 084fcad1fe
3 changed files with 18 additions and 65 deletions
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1
Makefile.am
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@ -214,6 +214,7 @@ GenOrdAST_SOURCES = pregen/GenOrdAST.hs $(pregen_sources)
GenTagAST_SOURCES = pregen/GenTagAST.hs $(pregen_sources)
rangetest_SOURCES = rangetest.c
rangetest_CFLAGS = -Wall
rangetest_LDFLAGS = -lm
#The programs to actually build:

9
rangetest.c
View File

@ -220,15 +220,6 @@ int main(int argc, char** argv)
check_all(2147483647,32);
check_all(9223372036854775807,64);
testf(occam_mul_int8_t(127,127,""));
testf(occam_mul_int8_t(2,127,""));
testf(occam_mul_int8_t(127,127,""));
testf(occam_mul_int8_t(127,-128,""));
testf(occam_mul_int8_t(-128,-128,""));
testf(occam_mul_int8_t(-1,-128,""));
testp(-128,occam_mul_int8_t(1,-128,""));
//TODO test multiply like the others
test_commutative(int8_t,occam_add_int8_t,add);
test_commutative(int8_t,occam_mul_int8_t,mult);

73
support/tock_support.h
View File

@ -141,66 +141,27 @@ static inline int occam_check_retype (int src, int dest, const char *pos) {
static inline type occam_subtr_##type (type, type, const char *) occam_unused; \
static inline type occam_subtr_##type (type a, type b, const char *pos) { return a - b;}
//Here is the plan:
// - For any values that are smaller than sizeof(long), cast them to long and check that way (TODO).
// - For all other values, split the number. Take N to be the length of the word
// and n to be N/2. Split the bits into top(A|B) and bottom(A|B) So we have:
//A = topA*2^n + bottomA
//B = topB*2^n + bottomB
//A*B = (topA*2^n + bottomA) * (topB*2^n + bottomB)
// = topA*topB*2^N + 2^n*(topA*bottomB + topB*bottomA) + (bottomA*bottomB)
//
//If topA*topB is non-zero, the multiplication will definitely overflow. So
//the multiplication can only be valid if either topA or topB is zero.
//Then we can see if the middle bracketed multiplication is >= 2^n, in which case
//the calculation would also overflow. Also, given that either topA or topB is zero,
//only one of the components of the bracketed sum is non-zero. Finally we do an occam add-style addition
//of the middle and end, again checking for overflow.
#define abs(x) ((x) < 0 ? -x : x)
/* This is my other attempt at the function, but it turned out slower:
const utype topA = (utype)abs(a) >> (sizeof(type)*CHAR_BIT/2); \
const utype topB = (utype)abs(b) >> (sizeof(type)*CHAR_BIT/2); \
const utype bottomA = (utype)abs(a) & (((utype)1<<(sizeof(type)*CHAR_BIT/2))-1); \
const utype bottomB = (utype)abs(b) & (((utype)1<<(sizeof(type)*CHAR_BIT/2))-1); \
const utype pos_res = ((a > 0 && b > 0) || (a < 0 && b < 0)) ? 1 : 0; \
if (topA != 0 && topB != 0) { \
occam_stop(pos,3,"integer overflow when doing %d * %d", a, b); \
} else { \
const utype mid = topA != 0 ? topA*bottomB : topB*bottomA; \
const utype mid_shift = mid << (sizeof(type)*CHAR_BIT/2); \
const utype low = bottomA*bottomB; \
if ((mid>>((utype)1<<(sizeof(type)*CHAR_BIT/2))==0)&&(((utype)__MAX(type))+1-pos_res-mid_shift>=low)) {\
return (pos_res == 1 ? (type)(mid_shift+low) : -(type)mid_shift-(type)low); \
} else { \
occam_stop(pos,3,"integer overflow when doing %d * %d", a, b); \
} \
} \
}
*/
#define MAKE_MUL(type,utype) \
#define MAKE_MUL(type) \
static inline type occam_mul_##type (type, type, const char *) occam_unused; \
static inline type occam_mul_##type (const type a, const type b, const char *pos) { \
if (( (a < 0 ? -a : a) >> ((sizeof(type)*CHAR_BIT/2)-1) \
| (b < 0 ? -b : b) >> ((sizeof(type)*CHAR_BIT/2)-1)) == 0) { \
/*overflow not possible on such small numbers*/ \
return a * b; \
} else if (b == 0) { \
return 0; \
} else { \
if (sizeof(type) < sizeof(long)) /*should be statically known*/ { \
const long r = (long)a * (long) b; \
if (r < (long)__MIN(type) || r > (long)__MAX(type)) { \
occam_stop(pos, 3, "integer overflow when doing %d * %d", a, b); \
} else { \
return (type)r; \
} \
} else { \
/* Taken from: http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg326431.html */ \
const type r = a * b; \
/* Taken from: http://www.mail-archive.com/debian-bugs-dist@lists.debian.org/msg326431.html */ \
if (r / b != a) { \
occam_stop(pos, 3, "integer overflow when doing %d * %d", a, b); \
} else { \
if (b != 0 && r / b != a) { \
occam_stop(pos, 3, "integer overflow when doing %d * %d", a, b); \
} else { \
return r; \
} \
} \
} \
}
#define MAKE_MULF(type) \
static inline type occam_mul_##type (type, type, const char *) occam_unused; \
static inline type occam_mul_##type (type a, type b, const char *pos) { return a * b;}
@ -302,7 +263,7 @@ static inline int occam_check_retype (int src, int dest, const char *pos) {
MAKE_RANGE_CHECK(type,flag) \
MAKE_ADD(type) \
MAKE_SUBTR(type) \
MAKE_MUL(type,utype) \
MAKE_MUL(type) \
MAKE_DIV(type) \
MAKE_REM(type) \
MAKE_NEGATE(type) \
@ -315,7 +276,7 @@ static inline int occam_check_retype (int src, int dest, const char *pos) {
MAKE_RANGE_CHECK(uint8_t, "%d")
MAKE_ADD(uint8_t)
MAKE_SUBTR(uint8_t)
MAKE_MUL(uint8_t,uint8_t)
MAKE_MUL(uint8_t)
MAKE_DIV(uint8_t)
MAKE_SHIFT(uint8_t,uint8_t)
MAKE_PLUS(uint8_t)