547 lines
13 KiB
C
547 lines
13 KiB
C
/* This file is part of the program psim.
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Copyright (C) 1994-1996, Andrew Cagney <cagney@highland.com.au>
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Copyright (C) 1997, Free Software Foundation, Inc.
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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; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifndef _SIM_ALU_H_
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#define _SIM_ALU_H_
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#include "sim-xcat.h"
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/* Binary addition, carry and overflow:
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Overflow - method 1:
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Overflow occures when the sign of the two operands is identical but
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different to the sign of the result:
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SIGN_BIT (~(a ^ b) & ((a + b) ^ b))
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Note that, for subtraction, care must be taken with MIN_INTn.
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Overflow - method 2:
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The two N bit operands are sign extended to M>N bits and then
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added. Overflow occures when SIGN_BIT<n> and SIGN_BIT<m> do not
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match.
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SIGN_BIT (r >> (M-N) ^ r)
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Overflow - method 3:
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The two N bit operands are sign extended to M>N bits and then
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added. Overflow occures when the result is outside of signextended
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MIN_INTn, MAX_INTn.
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Overflow - method 4:
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Given the carry bit, the overflow can be computed using the
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equation:
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SIGN_BIT (((A ^ B) ^ R) ^ C)
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As shown in the table below:
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I A B R C | V | A^B ^R ^C
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---------------+---+-------------
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0 0 0 0 0 | 0 | 0 0 0
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0 0 1 1 0 | 0 | 1 0 0
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0 1 0 1 0 | 0 | 1 0 0
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0 1 1 0 1 | 1 | 0 0 1
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1 0 0 1 0 | 1 | 0 1 1
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1 0 1 0 1 | 0 | 1 1 0
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1 1 0 0 1 | 0 | 1 1 0
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1 1 1 1 1 | 0 | 0 1 0
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Carry - method 1:
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Consider the truth table (carryIn, Result, Carryout, Result):
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I A B R | C
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------------+---
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0 0 0 0 | 0
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0 0 1 1 | 0
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0 1 0 1 | 0
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0 1 1 0 | 1
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1 0 0 1 | 0
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1 0 1 0 | 1
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1 1 0 0 | 1
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1 1 1 1 | 1
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Looking at the terms A, B and R we want an equation for C.
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AB\R 0 1
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+-------
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00 | 0 0
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01 | 1 0
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11 | 1 1
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10 | 1 0
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This giving us the sum-of-prod equation:
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SIGN_BIT ((A & B) | (A & ~R) | (B & ~R))
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Verifying:
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I A B R | C | A&B A&~R B&~R
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------------+---+---------------
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0 0 0 0 | 0 | 0 0 0
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0 0 1 1 | 0 | 0 0 0
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0 1 0 1 | 0 | 0 0 0
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0 1 1 0 | 1 | 1 1 1
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1 0 0 1 | 0 | 0 0 0
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1 0 1 0 | 1 | 0 0 1
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1 1 0 0 | 1 | 0 1 0
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1 1 1 1 | 1 | 1 0 0
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Carry - method 2:
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Given two signed N bit numbers, a carry can be detected by treating
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the numbers as N bit unsigned and adding them using M>N unsigned
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arrithmetic. Carry is indicated by bit (1 << N) being set (result
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>= 2**N).
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SIGN_BITm (r)
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Carry - method 3:
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Given the overflow bit. The carry can be computed from:
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(~R&V) | (R&V)
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Carry - method 4:
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Add the two signed N bit numbers as unsigned N bit numbers, and then
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compare the result to either one of the inputs via unsigned compare.
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If the result is less than the inputs, carry occurred.
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C = ((unsigned)(a+b)) < (unsigned)a if adding
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(or)
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C = (unsigned)a < (unsigned)b if subtracting
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*/
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/* 8 bit target expressions:
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Since the host's natural bitsize > 8 bits, carry method 2 and
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overflow method 2 are used. */
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#define ALU8_BEGIN(VAL) \
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signed alu8_cr = (unsigned8) (VAL); \
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unsigned alu8_vr = (signed8) (alu8_cr)
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#define ALU8_SET(VAL) \
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alu8_cr = (unsigned8) (VAL); \
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alu8_vr = (signed8) (alu8_cr)
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#define ALU8_SET_CARRY(CARRY) \
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do { \
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if (CARRY) \
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alu8_cr |= ((signed)-1) << 8; \
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else \
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alu8_cr &= 0xff; \
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} while (0)
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#define ALU8_HAD_CARRY (alu8_cr & LSBIT32(8))
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#define ALU8_HAD_OVERFLOW (((alu8_vr >> 8) ^ alu8_vr) & LSBIT32 (8-1))
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#define ALU8_RESULT ((unsigned8) alu8_cr)
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#define ALU8_CARRY_RESULT ((unsigned8) alu8_cr)
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#define ALU8_OVERFLOW_RESULT ((unsigned8) alu8_vr)
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/* #define ALU8_END ????? - target dependant */
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/* 16 bit target expressions:
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Since the host's natural bitsize > 16 bits, carry method 2 and
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overflow method 2 are used. */
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#define ALU16_BEGIN(VAL) \
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signed alu16_cr = (unsigned16) (VAL); \
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unsigned alu16_vr = (signed16) (alu16_cr)
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#define ALU16_SET(VAL) \
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alu16_cr = (unsigned16) (VAL); \
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alu16_vr = (signed16) (alu16_cr)
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#define ALU16_SET_CARRY(CARRY) \
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do { \
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if (CARRY) \
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alu16_cr |= ((signed)-1) << 16; \
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else \
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alu16_cr &= 0xffff; \
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} while (0)
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#define ALU16_HAD_CARRY (alu16_cr & LSBIT32(16))
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#define ALU16_HAD_OVERFLOW (((alu16_vr >> 16) ^ alu16_vr) & LSBIT32 (16-1))
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#define ALU16_RESULT ((unsigned16) alu16_cr)
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#define ALU16_CARRY_RESULT ((unsigned16) alu16_cr)
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#define ALU16_OVERFLOW_RESULT ((unsigned16) alu16_vr)
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/* #define ALU16_END ????? - target dependant */
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/* 32 bit target expressions:
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Since most hosts do not support 64 (> 32) bit arrithmetic, carry
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method 4 and overflow method 4 are used.
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FIXME: 64 bit hosts should use the same method as for the 16 bit
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ALU. */
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#define ALU32_BEGIN(VAL) \
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unsigned32 alu32_r = (VAL); \
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int alu32_c = 0; \
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int alu32_v = 0
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#define ALU32_SET(VAL) \
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alu32_r = (VAL); \
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alu32_c = 0; \
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alu32_v = 0
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#define ALU32_SET_CARRY(CARRY) alu32_c = (CARRY)
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#define ALU32_HAD_OVERFLOW (alu32_v)
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#define ALU32_HAD_CARRY (alu32_c)
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#define ALU32_RESULT (alu32_r)
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#define ALU32_CARRY_RESULT (alu32_r)
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#define ALU32_OVERFLOW_RESULT (alu32_r)
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/* 64 bit target expressions:
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Even though the host typically doesn't support native 64 bit
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arrithmetic, it is still used. */
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#define ALU64_BEGIN(VAL) \
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natural64 alu64_r = (VAL); \
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int alu64_c = 0; \
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int alu64_v = 0
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#define ALU64_SET(VAL) \
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alu64_r = (VAL); \
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alu64_c = 0; \
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alu64_v = 0
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#define ALU64_SET_CARRY(CARRY) alu64_c = (CARRY)
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#define ALU64_HAD_CARRY (alu64_c)
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#define ALU64_HAD_OVERFLOW (alu64_v)
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#define ALU64_RESULT (alu64_r)
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#define ALU64_CARRY_RESULT (alu64_r)
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#define ALU64_OVERFLOW_RESULT (alu64_r)
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/* Generic versions of above macros */
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#define ALU_BEGIN XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_BEGIN)
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#define ALU_SET XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_SET)
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#define ALU_SET_CARRY XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_SET_CARRY)
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#define ALU_HAD_OVERFLOW XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_HAD_OVERFLOW)
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#define ALU_HAD_CARRY XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_HAD_CARRY)
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#define ALU_RESULT XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_RESULT)
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#define ALU_OVERFLOW_RESULT XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_OVERFLOW_RESULT)
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#define ALU_CARRY_RESULT XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_CARRY_RESULT)
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/* Basic operations */
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#define ALU8_ADD(VAL) \
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do { \
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unsigned8 alu8_tmp = (VAL); \
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alu8_cr += (unsigned8)(alu8_tmp); \
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alu8_vr += (signed8)(alu8_tmp); \
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} while (0)
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#define ALU16_ADD(VAL) \
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do { \
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unsigned16 alu16_tmp = (VAL); \
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alu16_cr += (unsigned16)(alu16_tmp); \
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alu16_vr += (signed16)(alu16_tmp); \
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} while (0)
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#define ALU32_ADD(VAL) \
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do { \
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unsigned32 alu32_tmp = (unsigned32) (VAL); \
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unsigned32 alu32_sign = alu32_tmp ^ alu32_r; \
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alu32_r += (alu32_tmp); \
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alu32_c = (alu32_r < alu32_tmp); \
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alu32_v = ((alu32_sign ^ - (unsigned32)alu32_c) ^ alu32_r) >> 31; \
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} while (0)
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#define ALU64_ADD(VAL) \
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do { \
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unsigned64 alu64_tmp = (unsigned64) (VAL); \
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unsigned64 alu64_sign = alu64_tmp ^ alu64_r; \
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alu64_r += (alu64_tmp); \
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alu64_c = (alu64_r < alu64_tmp); \
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alu64_v = ((alu64_sign ^ - (unsigned64)alu64_c) ^ alu64_r) >> 63; \
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} while (0)
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#define ALU_ADD(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_ADD)(VAL)
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#define ALU8_ADD_CA(VAL) \
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do { \
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unsigned8 alu8_ca_tmp = (VAL) + ALU8_HAD_CARRY; \
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ALU8_ADD(alu8_ca_tmp); \
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} while (0)
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#define ALU16_ADD_CA(VAL) \
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do { \
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unsigned16 alu16_ca_tmp = (VAL) + ALU16_HAD_CARRY; \
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ALU16_ADD(alu16_ca_tmp); \
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} while (0)
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#define ALU32_ADD_CA(VAL) \
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do { \
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unsigned32 alu32_ca_tmp = (VAL) + ALU32_HAD_CARRY; \
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ALU32_ADD(alu32_ca_tmp); \
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} while (0)
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#define ALU64_ADD_CA(VAL) \
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do { \
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unsigned64 alu64_ca_tmp = (VAL) + ALU64_HAD_CARRY; \
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ALU64_ADD(alu64_ca_tmp); \
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} while (0)
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#define ALU_ADD_CA(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_ADD_CA)(VAL)
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/* Remember: Hardware implements subtract as an ADD with a carry in of
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1 into the least significant bit */
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#define ALU8_SUB(VAL) \
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do { \
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signed alu8sub_val = ~(VAL); \
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ALU8_ADD (alu8sub_val); \
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ALU8_ADD (1); \
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} while (0)
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#define ALU16_SUB(VAL) \
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do { \
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signed alu16sub_val = ~(VAL); \
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ALU16_ADD (alu16sub_val); \
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ALU16_ADD (1); \
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} while (0)
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#define ALU32_SUB(VAL) \
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do { \
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unsigned32 alu32_tmp = (unsigned32) (VAL); \
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unsigned32 alu32_sign = alu32_tmp ^ alu32_r; \
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alu32_c = (alu32_r < alu32_tmp); \
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alu32_r -= (alu32_tmp); \
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alu32_v = ((alu32_sign ^ - (unsigned32)alu32_c) ^ alu32_r) >> 31; \
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} while (0)
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#define ALU64_SUB(VAL) \
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do { \
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unsigned64 alu64_tmp = (unsigned64) (VAL); \
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unsigned64 alu64_sign = alu64_tmp ^ alu64_r; \
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alu64_c = (alu64_r < alu64_tmp); \
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alu64_r -= (alu64_tmp); \
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alu64_v = ((alu64_sign ^ - (unsigned64)alu64_c) ^ alu64_r) >> 63; \
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} while (0)
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#define ALU_SUB(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_SUB)(VAL)
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#define ALU8_SUB_CA(VAL) \
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do { \
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unsigned8 alu8_ca_tmp = (VAL) + ALU8_HAD_CARRY; \
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ALU8_SUB(alu8_ca_tmp); \
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} while (0)
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#define ALU16_SUB_CA(VAL) \
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do { \
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unsigned16 alu16_ca_tmp = (VAL) + ALU16_HAD_CARRY; \
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ALU16_SUB(alu16_ca_tmp); \
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} while (0)
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#define ALU32_SUB_CA(VAL) \
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do { \
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unsigned32 alu32_ca_tmp = (VAL) + ALU32_HAD_CARRY; \
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ALU32_SUB(alu32_ca_tmp); \
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} while (0)
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#define ALU64_SUB_CA(VAL) \
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do { \
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unsigned64 alu64_ca_tmp = (VAL) + ALU64_HAD_CARRY; \
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ALU64_SUB(alu64_ca_tmp); \
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} while (0)
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#define ALU_SUB_CA(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_SUB_CA)(VAL)
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#define ALU16_OR(VAL) \
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do { \
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error("ALU16_OR"); \
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} while (0)
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#define ALU32_OR(VAL) \
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do { \
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alu32_r |= (VAL); \
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alu32_c = 0; \
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alu32_v = 0; \
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} while (0)
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#define ALU64_OR(VAL) \
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do { \
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alu64_r |= (VAL); \
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alu64_c = 0; \
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alu64_v = 0; \
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} while (0)
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#define ALU_OR(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_OR)(VAL)
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#define ALU16_XOR(VAL) \
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do { \
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error("ALU16_XOR"); \
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} while (0)
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#define ALU32_XOR(VAL) \
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do { \
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alu32_r ^= (VAL); \
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alu32_c = 0; \
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alu32_v = 0; \
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} while (0)
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#define ALU64_XOR(VAL) \
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do { \
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alu64_r ^= (VAL); \
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alu64_c = 0; \
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alu64_v = 0; \
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} while (0)
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#define ALU_XOR(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_XOR)(VAL)
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#define ALU8_NEGATE() \
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do { \
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signed alu8neg_val = ~(ALU8_RESULT); \
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ALU8_SET (1); \
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ALU8_ADD (alu8neg_val); \
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} while (0)
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#define ALU16_NEGATE() \
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do { \
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signed alu16neg_val = ~(ALU16_RESULT); \
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ALU16_SET (1); \
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ALU16_ADD (alu16neg_val); \
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} while (0)
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#define ALU32_NEGATE() \
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do { \
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unsigned32 alu32_tmp_orig = alu32_r; \
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ALU32_SET (0); \
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ALU32_SUB (alu32_tmp_orig); \
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} while(0)
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#define ALU64_NEGATE() \
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do { \
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unsigned64 alu64_tmp_orig = alu64_r; \
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ALU64_SET (0); \
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ALU64_SUB (alu64_tmp_orig); \
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} while (0)
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#define ALU_NEGATE XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_NEGATE)
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#define ALU16_AND(VAL) \
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do { \
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error("ALU_AND16"); \
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} while (0)
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#define ALU32_AND(VAL) \
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do { \
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alu32_r &= (VAL); \
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alu32_r = 0; \
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alu32_v = 0; \
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} while (0)
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#define ALU64_AND(VAL) \
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do { \
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|
alu64_r &= (VAL); \
|
|
alu64_r = 0; \
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alu64_v = 0; \
|
|
} while (0)
|
|
|
|
#define ALU_AND(VAL) XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_AND)(VAL)
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|
|
|
|
|
|
|
|
|
#define ALU16_NOT(VAL) \
|
|
do { \
|
|
error("ALU_NOT16"); \
|
|
} while (0)
|
|
|
|
#define ALU32_NOT \
|
|
do { \
|
|
alu32_r = ~alu32_r; \
|
|
alu32_c = 0; \
|
|
alu32_v = 0; \
|
|
} while (0)
|
|
|
|
#define ALU64_NOT \
|
|
do { \
|
|
alu64_r = ~alu64_r; \
|
|
alu64_c = 0; \
|
|
alu64_v = 0; \
|
|
} while (0)
|
|
|
|
#define ALU_NOT XCONCAT3(ALU,WITH_TARGET_WORD_BITSIZE,_NOT)
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|
|
|
#endif
|