/* * Copyright 2004-2009 Analog Devices Inc. * * Licensed under the Clear BSD license or the GPL-2 (or later) * * 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 * */ .global ___divsi3; .type ___divsi3, STT_FUNC; #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; .size ___divsi3, .-___divsi3