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Diffstat (limited to 'arch/blackfin/lib/divsi3.S')
| -rw-r--r-- | arch/blackfin/lib/divsi3.S | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/arch/blackfin/lib/divsi3.S b/arch/blackfin/lib/divsi3.S new file mode 100644 index 00000000000..3e29861852b --- /dev/null +++ b/arch/blackfin/lib/divsi3.S @@ -0,0 +1,216 @@ +/* + * File: arch/blackfin/lib/divsi3.S + * Based on: + * Author: + * + * Created: + * Description: 16 / 32 bit signed division. + * Special cases : + * 1) If(numerator == 0) + * return 0 + * 2) If(denominator ==0) + * return positive max = 0x7fffffff + * 3) If(numerator == denominator) + * return 1 + * 4) If(denominator ==1) + * return numerator + * 5) If(denominator == -1) + * return -numerator + * + * Operand : R0 - Numerator (i) + * R1 - Denominator (i) + * R0 - Quotient (o) + * Registers Used : R2-R7,P0-P2 + * + * Modified: + * Copyright 2004-2006 Analog Devices Inc. + * + * Bugs: Enter bugs at http://blackfin.uclinux.org/ + * + * This program 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 2 of the License, or + * (at your option) any later version. + * + * This program 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 this program; if not, see the file COPYING, or write + * to the Free Software Foundation, Inc., + * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + */ + +.global ___divsi3; + +#ifdef CONFIG_ARITHMETIC_OPS_L1 +.section .l1.text +#else +.text +#endif + +.align 2; +___divsi3 : + + + R3 = R0 ^ R1; + R0 = ABS R0; + + CC = V; + + r3 = rot r3 by -1; + r1 = abs r1; /* now both positive, r3.30 means "negate result", + ** r3.31 means overflow, add one to result + */ + cc = r0 < r1; + if cc jump .Lret_zero; + r2 = r1 >> 15; + cc = r2; + if cc jump .Lidents; + r2 = r1 << 16; + cc = r2 <= r0; + if cc jump .Lidents; + + DIVS(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + DIVQ(R0, R1); + + R0 = R0.L (Z); + r1 = r3 >> 31; /* add overflow issue back in */ + r0 = r0 + r1; + r1 = -r0; + cc = bittst(r3, 30); + if cc r0 = r1; + RTS; + +/* Can't use the primitives. Test common identities. +** If the identity is true, return the value in R2. +*/ + +.Lidents: + CC = R1 == 0; /* check for divide by zero */ + IF CC JUMP .Lident_return; + + CC = R0 == 0; /* check for division of zero */ + IF CC JUMP .Lzero_return; + + CC = R0 == R1; /* check for identical operands */ + IF CC JUMP .Lident_return; + + CC = R1 == 1; /* check for divide by 1 */ + IF CC JUMP .Lident_return; + + R2.L = ONES R1; + R2 = R2.L (Z); + CC = R2 == 1; + IF CC JUMP .Lpower_of_two; + + /* Identities haven't helped either. + ** Perform the full division process. + */ + + P1 = 31; /* Set loop counter */ + + [--SP] = (R7:5); /* Push registers R5-R7 */ + R2 = -R1; + [--SP] = R2; + R2 = R0 << 1; /* R2 lsw of dividend */ + R6 = R0 ^ R1; /* Get sign */ + R5 = R6 >> 31; /* Shift sign to LSB */ + + R0 = 0 ; /* Clear msw partial remainder */ + R2 = R2 | R5; /* Shift quotient bit */ + R6 = R0 ^ R1; /* Get new quotient bit */ + + LSETUP(.Llst,.Llend) LC0 = P1; /* Setup loop */ +.Llst: R7 = R2 >> 31; /* record copy of carry from R2 */ + R2 = R2 << 1; /* Shift 64 bit dividend up by 1 bit */ + R0 = R0 << 1 || R5 = [SP]; + R0 = R0 | R7; /* and add carry */ + CC = R6 < 0; /* Check quotient(AQ) */ + /* we might be subtracting divisor (AQ==0) */ + IF CC R5 = R1; /* or we might be adding divisor (AQ==1)*/ + R0 = R0 + R5; /* do add or subtract, as indicated by AQ */ + R6 = R0 ^ R1; /* Generate next quotient bit */ + R5 = R6 >> 31; + /* Assume AQ==1, shift in zero */ + BITTGL(R5,0); /* tweak AQ to be what we want to shift in */ +.Llend: R2 = R2 + R5; /* and then set shifted-in value to + ** tweaked AQ. + */ + r1 = r3 >> 31; + r2 = r2 + r1; + cc = bittst(r3,30); + r0 = -r2; + if !cc r0 = r2; + SP += 4; + (R7:5)= [SP++]; /* Pop registers R6-R7 */ + RTS; + +.Lident_return: + CC = R1 == 0; /* check for divide by zero => 0x7fffffff */ + R2 = -1 (X); + R2 >>= 1; + IF CC JUMP .Ltrue_ident_return; + + CC = R0 == R1; /* check for identical operands => 1 */ + R2 = 1 (Z); + IF CC JUMP .Ltrue_ident_return; + + R2 = R0; /* assume divide by 1 => numerator */ + /*FALLTHRU*/ + +.Ltrue_ident_return: + R0 = R2; /* Return an identity value */ + R2 = -R2; + CC = bittst(R3,30); + IF CC R0 = R2; +.Lzero_return: + RTS; /* ...including zero */ + +.Lpower_of_two: + /* Y has a single bit set, which means it's a power of two. + ** That means we can perform the division just by shifting + ** X to the right the appropriate number of bits + */ + + /* signbits returns the number of sign bits, minus one. + ** 1=>30, 2=>29, ..., 0x40000000=>0. Which means we need + ** to shift right n-signbits spaces. It also means 0x80000000 + ** is a special case, because that *also* gives a signbits of 0 + */ + + R2 = R0 >> 31; + CC = R1 < 0; + IF CC JUMP .Ltrue_ident_return; + + R1.l = SIGNBITS R1; + R1 = R1.L (Z); + R1 += -30; + R0 = LSHIFT R0 by R1.L; + r1 = r3 >> 31; + r0 = r0 + r1; + R2 = -R0; // negate result if necessary + CC = bittst(R3,30); + IF CC R0 = R2; + RTS; + +.Lret_zero: + R0 = 0; + RTS; |