-/* flonum_multip.c - multiply two flonums
- Copyright (C) 1987, 1990, 1991 Free Software Foundation, Inc.
-
- This file is part of Gas, the GNU Assembler.
-
- The GNU assembler is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY. No author or distributor
- accepts responsibility to anyone for the consequences of using it
- or for whether it serves any particular purpose or works at all,
- unless he says so in writing. Refer to the GNU Assembler General
- Public License for full details.
-
- Everyone is granted permission to copy, modify and redistribute
- the GNU Assembler, but only under the conditions described in the
- GNU Assembler General Public License. A copy of this license is
- supposed to have been given to you along with the GNU Assembler
- so you can know your rights and responsibilities. It should be
- in a file named COPYING. Among other things, the copyright
- notice and this notice must be preserved on all copies. */
+/* flonum_mult.c - multiply two flonums
+ Copyright (C) 1987-2020 Free Software Foundation, Inc.
+ This file is part of GAS, the GNU Assembler.
+
+ GAS is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3, or (at your option)
+ any later version.
+
+ GAS is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
+ License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with GAS; see the file COPYING. If not, write to the Free
+ Software Foundation, 51 Franklin Street - Fifth Floor, Boston, MA
+ 02110-1301, USA. */
+
+#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 flonum_multip (a, b, product)
-const FLONUM_TYPE *a;
-const FLONUM_TYPE *b;
-FLONUM_TYPE *product;
+void
+flonum_multip (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 */
- 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. */
- int N; /* As in sum above. */
- int A; /* Which [] of a? */
- int B; /* Which [] of b? */
-
- if((a->sign!='-' && a->sign!='+') || (b->sign!='-' && b->sign!='+')) {
- /* ...
- Got to fail somehow. Any suggestions? */
- product->sign=0;
- return;
- }
- product -> sign = (a->sign == b->sign) ? '+' : '-';
- size_of_a = a -> leader - a -> low;
- size_of_b = b -> leader - b -> low;
- exponent = a -> exponent + b -> exponent;
- size_of_product = product -> high - product -> low;
- size_of_sum = size_of_a + size_of_b;
- 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. */
- }
- else
- {
- P = 0;
- }
- carry = 0;
- significant = 0;
- for (N = 0;
- N <= size_of_sum;
- N++)
+ 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. */
+ int N; /* As in sum above. */
+ int A; /* Which [] of a? */
+ int B; /* Which [] of b? */
+
+ if ((a->sign != '-' && a->sign != '+')
+ || (b->sign != '-' && b->sign != '+'))
+ {
+ /* Got to fail somehow. Any suggestions? */
+ product->sign = 0;
+ return;
+ }
+ product->sign = (a->sign == b->sign) ? '+' : '-';
+ size_of_a = a->leader - a->low;
+ size_of_b = b->leader - b->low;
+ exponent = a->exponent + b->exponent;
+ size_of_product = product->high - product->low;
+ size_of_sum = size_of_a + size_of_b;
+ 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. */
+ }
+ else
+ {
+ P = 0;
+ }
+ carry = 0;
+ significant = 0;
+ for (N = 0; N <= size_of_sum; N++)
+ {
+ work = carry;
+ carry = 0;
+ for (A = 0; A <= N; A++)
+ {
+ B = N - A;
+ if (A <= size_of_a && B <= size_of_b && B >= 0)
{
- work = carry;
- carry = 0;
- 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];
- carry += work >> LITTLENUM_NUMBER_OF_BITS;
- work &= LITTLENUM_MASK;
+ /* 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
- printf("work=%08x carry=%04x\n", work, carry);
+ printf ("work=%08x carry=%04x\n", work, carry);
#endif
- }
- }
- significant |= work;
- if (significant || P<0)
- {
- if (P >= 0)
- {
- product -> low [P] = work;
+ }
+ }
+ significant |= work;
+ if (significant || P < 0)
+ {
+ if (P >= 0)
+ {
+ product->low[P] = work;
#ifdef TRACE
- printf("P=%d. work[p]:=%04x\n", P, work);
+ printf ("P=%d. work[p]:=%04x\n", P, work);
#endif
- }
- P ++;
- }
- else
- {
- extra_product_positions ++;
- exponent ++;
- }
}
- /*
- * [P]-> position # size_of_sum + 1.
- * This is where 'carry' should go.
- */
+ P++;
+ }
+ else
+ {
+ extra_product_positions++;
+ exponent++;
+ }
+ }
+ /* [P]-> position # size_of_sum + 1.
+ This is where 'carry' should go. */
#ifdef TRACE
- printf("final carry =%04x\n", carry);
+ printf ("final carry =%04x\n", carry);
#endif
- if (carry)
- {
- if (extra_product_positions > 0)
- {
- product -> low [P] = carry;
- }
- else
- {
- /* 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 --)
- {
- work = * q;
- * q = carry;
- carry = work;
- }
- }
- }
- else
+ if (carry)
+ {
+ if (extra_product_positions > 0)
+ product->low[P] = carry;
+ else
+ {
+ /* 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--)
{
- P --;
+ work = *q;
+ *q = carry;
+ carry = work;
}
- product -> leader = product -> low + P;
- product -> exponent = exponent;
+ }
+ }
+ else
+ P--;
+ product->leader = product->low + P;
+ product->exponent = exponent;
}
-
-/* end: flonum_multip.c */
projects / deliverable / binutils-gdb.git / blobdiff