diff options
Diffstat (limited to 'gas/flonum-mult.c')
| -rw-r--r-- | gas/flonum-mult.c | 75 |
1 files changed, 32 insertions, 43 deletions
diff --git a/gas/flonum-mult.c b/gas/flonum-mult.c index 434a73b..9ecb63d 100644 --- a/gas/flonum-mult.c +++ b/gas/flonum-mult.c @@ -22,25 +22,22 @@ #include "flonum.h" /* plan for a . b => p(roduct) - - + +-------+-------+-/ /-+-------+-------+ | a | a | ... | a | a | | A | A-1 | | 1 | 0 | +-------+-------+-/ /-+-------+-------+ - - + +-------+-------+-/ /-+-------+-------+ | b | b | ... | b | b | | B | B-1 | | 1 | 0 | +-------+-------+-/ /-+-------+-------+ - - + +-------+-------+-/ /-+-------+-/ /-+-------+-------+ | p | p | ... | p | ... | p | p | | A+B+1| A+B | | N | | 1 | 0 | +-------+-------+-/ /-+-------+-/ /-+-------+-------+ - + /^\ (carry) a .b ... | ... a .b a .b A B | 0 1 0 0 @@ -56,49 +53,48 @@ | \ +----- P = > a .b N /__ i j - + N = 0 ... A+B - + for all i,j where i+j=N [i,j integers > 0] - + a[], b[], p[] may not intersect. Zero length factors signify 0 significant bits: treat as 0.0. 0.0 factors do the right thing. Zero length product OK. - + I chose the ForTran accent "foo[bar]" instead of the C accent "*garply" because I felt the ForTran way was more intuitive. The C way would probably yield better code on most C compilers. Dean Elsner. - (C style also gives deeper insight [to me] ... oh well ...) - */ + (C style also gives deeper insight [to me] ... oh well ...) */ -void +void flonum_multip (a, b, product) const FLONUM_TYPE *a; const FLONUM_TYPE *b; FLONUM_TYPE *product; { - int size_of_a; /* 0 origin */ - int size_of_b; /* 0 origin */ - int size_of_product; /* 0 origin */ - int size_of_sum; /* 0 origin */ - int extra_product_positions; /* 1 origin */ + int size_of_a; /* 0 origin */ + int size_of_b; /* 0 origin */ + int size_of_product; /* 0 origin */ + int size_of_sum; /* 0 origin */ + int extra_product_positions; /* 1 origin */ unsigned long work; unsigned long carry; long exponent; LITTLENUM_TYPE *q; long significant; /* TRUE when we emit a non-0 littlenum */ - /* ForTran accent follows. */ - int P; /* Scan product low-order -> high. */ + /* ForTran accent follows. */ + int P; /* Scan product low-order -> high. */ int N; /* As in sum above. */ - int A; /* Which [] of a? */ - int B; /* Which [] of b? */ + int A; /* Which [] of a? */ + int B; /* Which [] of b? */ - if ((a->sign != '-' && a->sign != '+') || (b->sign != '-' && b->sign != '+')) + if ((a->sign != '-' && a->sign != '+') + || (b->sign != '-' && b->sign != '+')) { - /* ... - Got to fail somehow. Any suggestions? */ + /* Got to fail somehow. Any suggestions? */ product->sign = 0; return; } @@ -111,8 +107,8 @@ flonum_multip (a, b, product) extra_product_positions = size_of_product - size_of_sum; if (extra_product_positions < 0) { - P = extra_product_positions; /* P < 0 */ - exponent -= extra_product_positions; /* Increases exponent. */ + P = extra_product_positions; /* P < 0 */ + exponent -= extra_product_positions; /* Increases exponent. */ } else { @@ -130,7 +126,8 @@ flonum_multip (a, b, product) if (A <= size_of_a && B <= size_of_b && B >= 0) { #ifdef TRACE - printf ("a:low[%d.]=%04x b:low[%d.]=%04x work_before=%08x\n", A, a->low[A], B, b->low[B], work); + printf ("a:low[%d.]=%04x b:low[%d.]=%04x work_before=%08x\n", + A, a->low[A], B, b->low[B], work); #endif /* Watch out for sign extension! Without the casts, on the DEC Alpha, the multiplication result is *signed* @@ -162,23 +159,19 @@ flonum_multip (a, b, product) exponent++; } } - /* - * [P]-> position # size_of_sum + 1. - * This is where 'carry' should go. - */ + /* [P]-> position # size_of_sum + 1. + This is where 'carry' should go. */ #ifdef TRACE printf ("final carry =%04x\n", carry); #endif if (carry) { if (extra_product_positions > 0) - { - product->low[P] = carry; - } + product->low[P] = carry; else { - /* No room at high order for carry littlenum. */ - /* Shift right 1 to make room for most significant littlenum. */ + /* No room at high order for carry littlenum. */ + /* Shift right 1 to make room for most significant littlenum. */ exponent++; P--; for (q = product->low + P; q >= product->low; q--) @@ -190,11 +183,7 @@ flonum_multip (a, b, product) } } else - { - P--; - } + P--; product->leader = product->low + P; product->exponent = exponent; } - -/* end of flonum_mult.c */ |