Blackfin arch: add assembly function for doing 64bit unsigned division
Signed-off-by: Mike Frysinger <michael.frysinger@analog.com> Signed-off-by: Bryan Wu <bryan.wu@analog.com>
This commit is contained in:
Mike Frysinger
Bryan Wu
parent
1c668d8246
commit
b0a68dc07e
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@ -4,7 +4,7 @@
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lib-y := \
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ashldi3.o ashrdi3.o lshrdi3.o \
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muldi3.o divsi3.o udivsi3.o modsi3.o umodsi3.o \
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muldi3.o divsi3.o udivsi3.o udivdi3.o modsi3.o umodsi3.o \
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checksum.o memcpy.o memset.o memcmp.o memchr.o memmove.o \
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strcmp.o strcpy.o strncmp.o strncpy.o \
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umulsi3_highpart.o smulsi3_highpart.o \
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@ -0,0 +1,375 @@
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/*
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* udivdi3.S - unsigned long long division
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*
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* Copyright 2003-2007 Analog Devices Inc.
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* Enter bugs at http://blackfin.uclinux.org/
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*
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* Licensed under the GPLv2 or later.
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*/
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#include <linux/linkage.h>
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#define CARRY AC0
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#ifdef CONFIG_ARITHMETIC_OPS_L1
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.section .l1.text
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#else
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.text
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#endif
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ENTRY(___udivdi3)
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R3 = [SP + 12];
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[--SP] = (R7:4, P5:3);
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/* Attempt to use divide primitive first; these will handle
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** most cases, and they're quick - avoids stalls incurred by
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** testing for identities.
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*/
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R4 = R2 | R3;
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CC = R4 == 0;
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IF CC JUMP .LDIV_BY_ZERO;
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R4.H = 0x8000;
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R4 >>>= 16; // R4 now 0xFFFF8000
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R5 = R0 | R2; // If either dividend or
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R4 = R5 & R4; // divisor have bits in
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CC = R4; // top half or low half's sign
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IF CC JUMP .LIDENTS; // bit, skip builtins.
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R4 = R1 | R3; // Also check top halves
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CC = R4;
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IF CC JUMP .LIDENTS;
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/* Can use the builtins. */
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AQ = CC; // Clear AQ (CC==0)
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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DIVQ(R0, R2);
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R0 = R0.L (Z);
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R1 = 0;
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(R7:4, P5:3) = [SP++];
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RTS;
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.LIDENTS:
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/* Test for common identities. Value to be returned is
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** placed in R6,R7.
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*/
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// Check for 0/y, return 0
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R4 = R0 | R1;
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CC = R4 == 0;
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IF CC JUMP .LRETURN_R0;
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// Check for x/x, return 1
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R6 = R0 - R2; // If x == y, then both R6 and R7 will be zero
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R7 = R1 - R3;
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R4 = R6 | R7; // making R4 zero.
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R6 += 1; // which would now make R6:R7==1.
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CC = R4 == 0;
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IF CC JUMP .LRETURN_IDENT;
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// Check for x/1, return x
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R6 = R0;
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R7 = R1;
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CC = R3 == 0;
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IF !CC JUMP .Lnexttest;
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CC = R2 == 1;
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IF CC JUMP .LRETURN_IDENT;
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.Lnexttest:
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R4.L = ONES R2; // check for div by power of two which
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R5.L = ONES R3; // can be done using a shift
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R6 = PACK (R5.L, R4.L);
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CC = R6 == 1;
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IF CC JUMP .Lpower_of_two_upper_zero;
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R6 = PACK (R4.L, R5.L);
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CC = R6 == 1;
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IF CC JUMP .Lpower_of_two_lower_zero;
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// Check for x < y, return 0
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R6 = 0;
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R7 = R6;
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CC = R1 < R3 (IU);
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IF CC JUMP .LRETURN_IDENT;
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CC = R1 == R3;
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IF !CC JUMP .Lno_idents;
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CC = R0 < R2 (IU);
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IF CC JUMP .LRETURN_IDENT;
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.Lno_idents: // Idents don't match. Go for the full operation
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// If X, or X and Y have high bit set, it'll affect the
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// results, so shift right one to stop this. Note: we've already
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// checked that X >= Y, so Y's msb won't be set unless X's
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// is.
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R4 = 0;
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CC = R1 < 0;
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IF !CC JUMP .Lx_msb_clear;
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CC = !CC; // 1 -> 0;
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R1 = ROT R1 BY -1; // Shift X >> 1
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R0 = ROT R0 BY -1; // lsb -> CC
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BITSET(R4,31); // to record only x msb was set
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CC = R3 < 0;
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IF !CC JUMP .Ly_msb_clear;
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CC = !CC;
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R3 = ROT R3 BY -1; // Shift Y >> 1
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R2 = ROT R2 BY -1;
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BITCLR(R4,31); // clear bit to record only x msb was set
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.Ly_msb_clear:
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.Lx_msb_clear:
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// Bit 31 in R4 indicates X msb set, but Y msb wasn't, and no bits
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// were lost, so we should shift result left by one.
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[--SP] = R4; // save for later
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// In the loop that follows, each iteration we add
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// either Y' or -Y' to the Remainder. We compute the
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// negated Y', and store, for convenience. Y' goes
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// into P0:P1, while -Y' goes into P2:P3.
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P0 = R2;
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P1 = R3;
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R2 = -R2;
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CC = CARRY;
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CC = !CC;
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R4 = CC;
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R3 = -R3;
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R3 = R3 - R4;
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R6 = 0; // remainder = 0
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R7 = R6;
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[--SP] = R2; P2 = SP;
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[--SP] = R3; P3 = SP;
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[--SP] = R6; P5 = SP; // AQ = 0
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[--SP] = P1;
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/* In the loop that follows, we use the following
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** register assignments:
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** R0,R1 X, workspace
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** R2,R3 Y, workspace
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** R4,R5 partial Div
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** R6,R7 partial remainder
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** P5 AQ
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** The remainder and div form a 128-bit number, with
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** the remainder in the high 64-bits.
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*/
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R4 = R0; // Div = X'
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R5 = R1;
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R3 = 0;
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P4 = 64; // Iterate once per bit
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LSETUP(.LULST,.LULEND) LC0 = P4;
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.LULST:
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/* Shift Div and remainder up by one. The bit shifted
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** out of the top of the quotient is shifted into the bottom
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** of the remainder.
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*/
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CC = R3;
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R4 = ROT R4 BY 1;
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R5 = ROT R5 BY 1 || // low q to high q
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R2 = [P5]; // load saved AQ
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R6 = ROT R6 BY 1 || // high q to low r
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R0 = [P2]; // load -Y'
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R7 = ROT R7 BY 1 || // low r to high r
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R1 = [P3];
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// Assume add -Y'
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CC = R2 < 0; // But if AQ is set...
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IF CC R0 = P0; // then add Y' instead
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IF CC R1 = P1;
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R6 = R6 + R0; // Rem += (Y' or -Y')
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CC = CARRY;
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R0 = CC;
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R7 = R7 + R1;
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R7 = R7 + R0 (NS) ||
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R1 = [SP];
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// Set the next AQ bit
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R1 = R7 ^ R1; // from Remainder and Y'
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R1 = R1 >> 31 || // Negate AQ's value, and
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[P5] = R1; // save next AQ
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BITTGL(R1, 0); // add neg AQ to the Div
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.LULEND: R4 = R4 + R1;
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R6 = [SP + 16];
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R0 = R4;
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R1 = R5;
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CC = BITTST(R6,30); // Just set CC=0
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R4 = ROT R0 BY 1; // but if we had to shift X,
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R5 = ROT R1 BY 1; // and didn't shift any bits out,
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CC = BITTST(R6,31); // then the result will be half as
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IF CC R0 = R4; // much as required, so shift left
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IF CC R1 = R5; // one space.
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SP += 20;
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(R7:4, P5:3) = [SP++];
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RTS;
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.Lpower_of_two:
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/* Y has a single bit set, which means it's a power of two.
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** That means we can perform the division just by shifting
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** X to the right the appropriate number of bits
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*/
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/* signbits returns the number of sign bits, minus one.
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** 1=>30, 2=>29, ..., 0x40000000=>0. Which means we need
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** to shift right n-signbits spaces. It also means 0x80000000
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** is a special case, because that *also* gives a signbits of 0
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*/
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.Lpower_of_two_lower_zero:
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R7 = 0;
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R6 = R1 >> 31;
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CC = R3 < 0;
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IF CC JUMP .LRETURN_IDENT;
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R2.L = SIGNBITS R3;
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R2 = R2.L (Z);
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R2 += -62;
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(R7:4, P5:3) = [SP++];
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JUMP ___lshftli;
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.Lpower_of_two_upper_zero:
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CC = R2 < 0;
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IF CC JUMP .Lmaxint_shift;
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R2.L = SIGNBITS R2;
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R2 = R2.L (Z);
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R2 += -30;
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(R7:4, P5:3) = [SP++];
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JUMP ___lshftli;
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.Lmaxint_shift:
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R2 = -31;
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(R7:4, P5:3) = [SP++];
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JUMP ___lshftli;
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.LRETURN_IDENT:
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R0 = R6;
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R1 = R7;
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.LRETURN_R0:
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(R7:4, P5:3) = [SP++];
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RTS;
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.LDIV_BY_ZERO:
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R0 = ~R2;
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R1 = R0;
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(R7:4, P5:3) = [SP++];
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RTS;
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ENDPROC(___udivdi3)
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ENTRY(___lshftli)
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CC = R2 == 0;
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IF CC JUMP .Lfinished; // nothing to do
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CC = R2 < 0;
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IF CC JUMP .Lrshift;
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R3 = 64;
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CC = R2 < R3;
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IF !CC JUMP .Lretzero;
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// We're shifting left, and it's less than 64 bits, so
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// a valid result will be returned.
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R3 >>= 1; // R3 now 32
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CC = R2 < R3;
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IF !CC JUMP .Lzerohalf;
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// We're shifting left, between 1 and 31 bits, which means
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// some of the low half will be shifted into the high half.
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// Work out how much.
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R3 = R3 - R2;
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// Save that much data from the bottom half.
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P1 = R7;
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R7 = R0;
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R7 >>= R3;
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// Adjust both parts of the parameter.
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R0 <<= R2;
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R1 <<= R2;
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// And include the bits moved across.
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R1 = R1 | R7;
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R7 = P1;
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RTS;
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.Lzerohalf:
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// We're shifting left, between 32 and 63 bits, so the
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// bottom half will become zero, and the top half will
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// lose some bits. How many?
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R2 = R2 - R3; // N - 32
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R1 = LSHIFT R0 BY R2.L;
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R0 = R0 - R0;
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RTS;
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.Lretzero:
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R0 = R0 - R0;
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R1 = R0;
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.Lfinished:
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RTS;
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.Lrshift:
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// We're shifting right, but by how much?
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R2 = -R2;
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R3 = 64;
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CC = R2 < R3;
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IF !CC JUMP .Lretzero;
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// Shifting right less than 64 bits, so some result bits will
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// be retained.
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R3 >>= 1; // R3 now 32
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CC = R2 < R3;
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IF !CC JUMP .Lsignhalf;
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// Shifting right between 1 and 31 bits, so need to copy
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// data across words.
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P1 = R7;
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R3 = R3 - R2;
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R7 = R1;
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R7 <<= R3;
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R1 >>= R2;
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R0 >>= R2;
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R0 = R7 | R0;
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R7 = P1;
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RTS;
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.Lsignhalf:
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// Shifting right between 32 and 63 bits, so the top half
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// will become all zero-bits, and the bottom half is some
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// of the top half. But how much?
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R2 = R2 - R3;
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R0 = R1;
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R0 >>= R2;
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R1 = 0;
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RTS;
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ENDPROC(___lshftli)
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