/* flonum_mult.c - multiply two flonums
- Copyright (C) 1987, 1990, 1991, 1992 Free Software Foundation, Inc.
+ Copyright 1987, 1990, 1991, 1992, 1995, 2000
+ Free Software Foundation, Inc.
This file is part of Gas, the GNU Assembler.
in a file named COPYING. Among other things, the copyright
notice and this notice must be preserved on all copies. */
+#include <ansidecl.h>
#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
| \
+----- 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 ...) */
\f
-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;
}
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
{
}
carry = 0;
significant = 0;
- for (N = 0;
- N <= size_of_sum;
- N++)
+ for (N = 0; N <= size_of_sum; N++)
{
work = carry;
carry = 0;
- for (A = 0;
- A <= N;
- A++)
+ for (A = 0; A <= N; A++)
{
B = N - A;
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
- work += a->low[A] * b->low[B];
+ /* Watch out for sign extension! Without the casts, on
+ the DEC Alpha, the multiplication result is *signed*
+ int, which gets sign-extended to convert to the
+ unsigned long! */
+ work += (unsigned long) a->low[A] * (unsigned long) b->low[B];
carry += work >> LITTLENUM_NUMBER_OF_BITS;
work &= LITTLENUM_MASK;
#ifdef TRACE
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--)
+ for (q = product->low + P; q >= product->low; q--)
{
work = *q;
*q = carry;
}
}
else
- {
- P--;
- }
+ P--;
product->leader = product->low + P;
product->exponent = exponent;
}
-
-/* end of flonum_mult.c */
projects / deliverable / binutils-gdb.git / blobdiff