suzanne.soy/tock-mirror
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Implemented LONGDIV (passes the cgtests, but I'm not 100% confident in it)

Browse Source
This commit is contained in:
Neil Brown 2009-01-26 18:03:27 +00:00
parent 4a12999989
commit 8df1bc80f9
1 changed files with 58 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
support/tock_intrinsics_arith.h
View File

@ -142,15 +142,69 @@ static inline INT occam_NORMALISE (INT hi_in, INT lo_in, INT* result1, INT* resu
}
}
////////////////////
//TODO implement, and move into the correct order above:
///////////////////
//Has to go late on due to its function re-use:
static inline INT occam_LONGDIV (INT, INT, INT, INT*, const char *) occam_unused;
static inline INT occam_LONGDIV (INT dividend_hi, INT dividend_lo, INT divisor, INT* result1, const char *pos) {
return 0;
UINT top_hi = occam_unsign(dividend_hi);
UINT top_lo = occam_unsign(dividend_lo);
const UINT bottom = occam_unsign(divisor);
//Intuititively, the algorithm works as follows:
//We work out how many Hi there are remaining in the
//Hi part after the Hi/Bot division. We then have
//Hi%Bot loads of R left. We can immediately
//add Hi%Bot * R/bot to the result, leaving
// Hi%Bot * R%Bot left. We must (long-)add this
//quantity to Lo, and repeat the procedure, until
// Hi is zero.
if (bottom == 0) {
occam_stop(pos, 1, "Division by zero in LONGDIV");
} else {
UINT r_hi = 0;
UINT r_lo = 0;
UINT amount_extra_R_over_bot = 0;
//We can work R/bot out by doing:
// (R/2)/bot + ((R/2)%bot + (R/2)/bot
const UINT halfR = occam_unsign(__MIN(INT));
UINT R_over_bot = bottom >= halfR ? 1 : (halfR/bottom + ((halfR % bottom) + halfR) / bottom);
UINT R_mod_bot = (__MAX(UINT)%bottom) == bottom - 1 ? 0 : 1+(__MAX(UINT)%bottom);
while (top_hi != 0) {
r_hi += top_hi / bottom;
r_lo += top_lo / bottom;
top_lo %= bottom;
top_hi %= bottom;
amount_extra_R_over_bot += top_hi;
top_hi = occam_unsign(occam_LONGPROD(occam_sign(top_hi),occam_sign(R_mod_bot),occam_sign(top_lo),(INT*)&top_lo,pos));
}
//long-add the results from top_lo/bottom to r_hi,r_lo:
r_hi += occam_unsign(occam_LONGSUM(occam_sign(r_lo),occam_sign(top_lo/bottom),0,(INT*)&r_lo,pos));
//Save the remainder for later:
const UINT rem = top_lo%bottom;
//Finally, add on R_over_bot * amount_extra_R_over_bot
top_hi = occam_unsign(occam_LONGPROD(occam_sign(R_over_bot), occam_sign(amount_extra_R_over_bot), 0, (INT*)&top_lo,pos));
r_hi += top_hi + occam_unsign(occam_LONGSUM(occam_sign(r_lo), occam_sign(top_lo), 0, (INT*)&r_lo, pos));
if (r_hi == 0) {
*result1 = occam_sign(rem);
return occam_sign(r_lo);
} else {
occam_stop(pos,4,"Overflow in LONGDIV(%d,%d,%d)", dividend_hi, dividend_lo, divisor);
}
}
}
////////////////////
//TODO implement, and move into the correct order above:
///////////////////
static inline INT occam_SHIFTRIGHT (INT, INT, INT, INT*, const char *) occam_unused;
static inline INT occam_SHIFTRIGHT (INT hi_in, INT lo_in, INT places, INT* result1, const char *pos) {
return 0;