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[/] [zipcpu/] [trunk/] [sw/] [zasm/] [twoc.cpp] - Diff between revs 2 and 69

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////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////
//
//
// Filename:    twoc.cpp
// Filename:    twoc.cpp
//
//
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
//
//
// Purpose:     Some various two's complement related C++ helper routines.
// Purpose:     Some various two's complement related C++ helper routines.
//              Specifically, these help extract signed numbers from
//              Specifically, these help extract signed numbers from
//              packed bitfields, while guaranteeing that the upper bits
//              packed bitfields, while guaranteeing that the upper bits
//              are properly sign extended (or not) as desired.
//              are properly sign extended (or not) as desired.
//
//
// Creator:     Dan Gisselquist, Ph.D.
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Tecnology, LLC
//              Gisselquist Technology, LLC
//
//
///////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////
//
//
// Copyright (C) 2015, Gisselquist Technology, LLC
// Copyright (C) 2015, Gisselquist Technology, LLC
//
//
// This program is free software (firmware): you can redistribute it and/or
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
// your option) any later version.
//
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
// for more details.
//
//
// You should have received a copy of the GNU General Public License along
// You should have received a copy of the GNU General Public License along
// with this program.  (It's in the $(ROOT)/doc directory, run make with no
// with this program.  (It's in the $(ROOT)/doc directory, run make with no
// target there if the PDF file isn't present.)  If not, see
// target there if the PDF file isn't present.)  If not, see
// <http://www.gnu.org/licenses/> for a copy.
// <http://www.gnu.org/licenses/> for a copy.
//
//
// License:     GPL, v3, as defined and found on www.gnu.org,
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//              http://www.gnu.org/licenses/gpl.html
//
//
//
//
///////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////
#include <stdio.h>
#include <stdio.h>
#include <assert.h>
#include <assert.h>
#include "twoc.h"
#include "twoc.h"
 
 
long    sbits(const long val, const int bits) {
long    sbits(const long val, const int bits) {
        long    r;
        long    r;
 
 
        r = val & ((1l<<bits)-1);
        r = val & ((1l<<bits)-1);
        if (r & (1l << (bits-1)))
        if (r & (1l << (bits-1)))
                r |= (-1l << bits);
                r |= (-1l << bits);
        return r;
        return r;
}
}
 
 
bool    sfits(const long val, const int bits) {
bool    sfits(const long val, const int bits) {
        long    alt = sbits(val, bits);
        long    alt = sbits(val, bits);
        return (sbits(val, bits) == bits);
        return (sbits(val, bits) == bits);
}
}
 
 
unsigned long   ubits(const long val, const int bits) {
unsigned long   ubits(const long val, const int bits) {
        unsigned long r = val & ((1l<<bits)-1);
        unsigned long r = val & ((1l<<bits)-1);
        return r;
        return r;
}
}
 
 
unsigned long   rndbits(const long val, const int bits_in, const int bits_out) {
unsigned long   rndbits(const long val, const int bits_in, const int bits_out) {
        long    s = sbits(val, bits_in); // Signed input value
        long    s = sbits(val, bits_in); // Signed input value
        long    t = s;  // Truncated input value
        long    t = s;  // Truncated input value
        long    r;      // Result
        long    r;      // Result
 
 
        // printf("RNDBITS(%08lx, %d, %d)\n", val, bits_in, bits_out);
        // printf("RNDBITS(%08lx, %d, %d)\n", val, bits_in, bits_out);
        // printf("S = %lx\n", s);
        // printf("S = %lx\n", s);
        // printf("T = %lx\n", t);
        // printf("T = %lx\n", t);
        // assert(bits_in > bits_out);
        // assert(bits_in > bits_out);
        if (bits_in == bits_out)
        if (bits_in == bits_out)
                r = s;
                r = s;
        else if (bits_in-1 == bits_out) {
        else if (bits_in-1 == bits_out) {
                t = sbits(val>>1, bits_out);
                t = sbits(val>>1, bits_out);
                // printf("TEST! S = %ld, T = %ld\n", s, t);
                // printf("TEST! S = %ld, T = %ld\n", s, t);
                if (3 == (s&3))
                if (3 == (s&3))
                        t = t+1;
                        t = t+1;
                r = t;
                r = t;
        } else {
        } else {
                // A. 0XXXX.0xxxxx -> 0XXXX
                // A. 0XXXX.0xxxxx -> 0XXXX
                // B. 0XXX0.100000 -> 0XXX0;
                // B. 0XXX0.100000 -> 0XXX0;
                // C. 0XXX1.100000 -> 0XXX1+1;
                // C. 0XXX1.100000 -> 0XXX1+1;
                // D. 0XXXX.1zzzzz -> 0XXXX+1;
                // D. 0XXXX.1zzzzz -> 0XXXX+1;
                // E. 1XXXX.0xxxxx -> 1XXXX
                // E. 1XXXX.0xxxxx -> 1XXXX
                // F. 1XXX0.100000 ->  ??? XXX0;
                // F. 1XXX0.100000 ->  ??? XXX0;
                // G. 1XXX1.100000 ->  ??? XXX1+1;
                // G. 1XXX1.100000 ->  ??? XXX1+1;
                // H. 1XXXX.1zzzzz -> 1XXXX+1;
                // H. 1XXXX.1zzzzz -> 1XXXX+1;
                t = sbits(val>>(bits_in-bits_out), bits_out); // Truncated value
                t = sbits(val>>(bits_in-bits_out), bits_out); // Truncated value
                if (0 == ((s >> (bits_in-bits_out-1))&1)) {
                if (0 == ((s >> (bits_in-bits_out-1))&1)) {
                        // printf("A\n");
                        // printf("A\n");
                        r = t;
                        r = t;
                } else if (0 != (s & ((1<<(bits_in-bits_out-1))-1))) {
                } else if (0 != (s & ((1<<(bits_in-bits_out-1))-1))) {
                        // printf("D\n");
                        // printf("D\n");
                        r = t+1;
                        r = t+1;
                } else if (t&1) {
                } else if (t&1) {
                        // printf("C\n");
                        // printf("C\n");
                        r = t+1;
                        r = t+1;
                } else { // 3 ..?11
                } else { // 3 ..?11
                        // printf("B\n");
                        // printf("B\n");
                        r = t;
                        r = t;
                }
                }
        } return r;
        } return r;
}
}
 
 
 
 
 
 

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