89 lines
3.4 KiB
C
89 lines
3.4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "tool/build/lib/alu.h"
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#include "tool/build/lib/flags.h"
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/**
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* NexGen32e Arithmetic Unit.
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*/
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int64_t Alu(int w, int h, uint64_t x, uint64_t y, uint32_t *flags) {
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uint64_t t, z, s, m, k;
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bool cf, of, zf, sf, af, carry;
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assert(w < 4);
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k = 8;
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k <<= w;
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s = 1;
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s <<= k - 1;
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m = s;
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m |= s - 1;
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t = x;
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cf = 0;
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of = 0;
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af = 0;
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carry = GetFlag(*flags, FLAGS_CF);
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switch (h & 7) {
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case ALU_OR:
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z = x | y;
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break;
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case ALU_AND:
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z = x & y;
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break;
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case ALU_XOR:
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z = x ^ y;
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break;
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case ALU_CMP:
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h |= 8;
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carry = 0;
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case ALU_SBB:
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t = (x & m) - carry;
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cf = (x & m) < (t & m);
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af = (x & 15) < (t & 15);
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case ALU_SUB:
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z = (t & m) - (y & m);
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cf |= (t & m) < (z & m);
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af |= (t & 15) < (z & 15);
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of = !!((z ^ x) & (x ^ y) & s);
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break;
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case ALU_ADC:
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t = (x & m) + carry;
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cf = (t & m) < (x & m);
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af = (t & 15) < (x & 15);
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case ALU_ADD:
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z = (t & m) + (y & m);
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cf |= (z & m) < (y & m);
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af |= (z & 15) < (y & 15);
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of = !!((z ^ x) & (z ^ y) & s);
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break;
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default:
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unreachable;
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}
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z &= m;
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zf = !z;
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sf = !!(z & s);
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*flags = (*flags & ~(1 << FLAGS_CF | 1 << FLAGS_ZF | 1 << FLAGS_SF |
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1 << FLAGS_OF | 1 << FLAGS_AF)) |
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cf << FLAGS_CF | zf << FLAGS_ZF | sf << FLAGS_SF | of << FLAGS_OF |
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af << FLAGS_AF;
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*flags = SetLazyParityByte(*flags, x);
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if (h & ALU_TEST) z = x;
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return z;
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}
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