276 lines
7.3 KiB
C++
276 lines
7.3 KiB
C++
// Copyright (C) 2003 Dolphin Project.
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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 2.0.
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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 2.0 for more details.
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// A copy of the GPL 2.0 should have been included with the program.
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// If not, see http://www.gnu.org/licenses/
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// Official SVN repository and contact information can be found at
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// http://code.google.com/p/dolphin-emu/
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// Additional copyrights go to Duddie and Tratax (c) 2004
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#include "DSPInterpreter.h"
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#include "DSPCore.h"
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#include "DSPMemoryMap.h"
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#include "DSPStacks.h"
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#include "DSPIntCCUtil.h"
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#include "DSPIntUtil.h"
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namespace DSPInterpreter {
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// Generic call implementation
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// CALLcc addressA
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// 0000 0010 1011 cccc
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// aaaa aaaa aaaa aaaa
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// Call function if condition cc has been met. Push program counter of
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// instruction following "call" to $st0. Set program counter to address
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// represented by value that follows this "call" instruction.
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void call(const UDSPInstruction opc)
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{
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// must be outside the if.
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u16 dest = dsp_fetch_code();
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if (CheckCondition(opc & 0xf))
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{
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dsp_reg_store_stack(DSP_STACK_C, g_dsp.pc);
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g_dsp.pc = dest;
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}
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}
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// Generic callr implementation
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// CALLRcc $R
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// 0001 0111 rrr1 cccc
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// Call function if condition cc has been met. Push program counter of
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// instruction following "call" to call stack $st0. Set program counter to
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// register $R.
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void callr(const UDSPInstruction opc)
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{
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if (CheckCondition(opc & 0xf))
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{
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u8 reg = (opc >> 5) & 0x7;
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u16 addr = dsp_op_read_reg(reg);
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dsp_reg_store_stack(DSP_STACK_C, g_dsp.pc);
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g_dsp.pc = addr;
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}
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}
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// Generic if implementation
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// IFcc
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// 0000 0010 0111 cccc
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// Execute following opcode if the condition has been met.
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void ifcc(const UDSPInstruction opc)
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{
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if (!CheckCondition(opc & 0xf))
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{
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// skip the next opcode - we have to lookup its size.
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dsp_skip_inst();
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}
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}
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// Generic jmp implementation
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// Jcc addressA
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// 0000 0010 1001 cccc
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// aaaa aaaa aaaa aaaa
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// Jump to addressA if condition cc has been met. Set program counter to
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// address represented by value that follows this "jmp" instruction.
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void jcc(const UDSPInstruction opc)
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{
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u16 dest = dsp_fetch_code();
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if (CheckCondition(opc & 0xf))
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{
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g_dsp.pc = dest;
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}
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}
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// Generic jmpr implementation
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// JMPcc $R
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// 0001 0111 rrr0 cccc
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// Jump to address; set program counter to a value from register $R.
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void jmprcc(const UDSPInstruction opc)
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{
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if (CheckCondition(opc & 0xf))
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{
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u8 reg = (opc >> 5) & 0x7;
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g_dsp.pc = dsp_op_read_reg(reg);
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}
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}
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// Generic ret implementation
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// RETcc
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// 0000 0010 1101 cccc
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// Return from subroutine if condition cc has been met. Pops stored PC
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// from call stack $st0 and sets $pc to this location.
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void ret(const UDSPInstruction opc)
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{
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if (CheckCondition(opc & 0xf))
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{
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g_dsp.pc = dsp_reg_load_stack(DSP_STACK_C);
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}
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}
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// RTI
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// 0000 0010 1111 1111
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// Return from exception. Pops stored status register $sr from data stack
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// $st1 and program counter PC from call stack $st0 and sets $pc to this
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// location.
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void rti(const UDSPInstruction opc)
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{
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g_dsp.r[DSP_REG_SR] = dsp_reg_load_stack(DSP_STACK_D);
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g_dsp.pc = dsp_reg_load_stack(DSP_STACK_C);
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}
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// HALT
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// 0000 0000 0020 0001
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// Stops execution of DSP code. Sets bit DSP_CR_HALT in register DREG_CR.
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void halt(const UDSPInstruction opc)
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{
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g_dsp.cr |= 0x4;
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g_dsp.pc--;
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}
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// LOOP handling: Loop stack is used to control execution of repeated blocks of
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// instructions. Whenever there is value on stack $st2 and current PC is equal
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// value at $st2, then value at stack $st3 is decremented. If value is not zero
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// then PC is modified with value from call stack $st0. Otherwise values from
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// call stack $st0 and both loop stacks $st2 and $st3 are popped and execution
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// continues at next opcode.
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void HandleLoop()
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{
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// Handle looping hardware.
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const u16 rCallAddress = g_dsp.r[DSP_REG_ST0];
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const u16 rLoopAddress = g_dsp.r[DSP_REG_ST2];
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u16& rLoopCounter = g_dsp.r[DSP_REG_ST3];
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if (rLoopAddress > 0 && rLoopCounter > 0)
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{
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// FIXME: why -1? because we just read past it.
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if (g_dsp.pc - 1 == rLoopAddress)
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{
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rLoopCounter--;
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if (rLoopCounter > 0)
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{
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g_dsp.pc = rCallAddress;
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}
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else
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{
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// end of loop
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dsp_reg_load_stack(0);
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dsp_reg_load_stack(2);
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dsp_reg_load_stack(3);
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}
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}
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}
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}
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// LOOP $R
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// 0000 0000 010r rrrr
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// Repeatedly execute following opcode until counter specified by value
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// from register $R reaches zero. Each execution decrement counter. Register
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// $R remains unchanged. If register $R is set to zero at the beginning of loop
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// then looped instruction will not get executed.
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// Actually, this instruction simply prepares the loop stacks for the above.
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// The looping hardware takes care of the rest.
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void loop(const UDSPInstruction opc)
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{
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u16 reg = opc & 0x1f;
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u16 cnt = g_dsp.r[reg];
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u16 loop_pc = g_dsp.pc;
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if (cnt)
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{
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dsp_reg_store_stack(0, g_dsp.pc);
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dsp_reg_store_stack(2, loop_pc);
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dsp_reg_store_stack(3, cnt);
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}
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}
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// LOOPI #I
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// 0001 0000 iiii iiii
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// Repeatedly execute following opcode until counter specified by
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// immediate value I reaches zero. Each execution decrement counter. If
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// immediate value I is set to zero at the beginning of loop then looped
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// instruction will not get executed.
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// Actually, this instruction simply prepares the loop stacks for the above.
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// The looping hardware takes care of the rest.
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void loopi(const UDSPInstruction opc)
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{
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u16 cnt = opc & 0xff;
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u16 loop_pc = g_dsp.pc;
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if (cnt)
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{
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dsp_reg_store_stack(0, g_dsp.pc);
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dsp_reg_store_stack(2, loop_pc);
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dsp_reg_store_stack(3, cnt);
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}
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}
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// BLOOP $R, addrA
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// 0000 0000 011r rrrr
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// aaaa aaaa aaaa aaaa
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// Repeatedly execute block of code starting at following opcode until
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// counter specified by value from register $R reaches zero. Block ends at
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// specified address addrA inclusive, ie. opcode at addrA is the last opcode
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// included in loop. Counter is pushed on loop stack $st3, end of block address
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// is pushed on loop stack $st2 and repeat address is pushed on call stack $st0.
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// Up to 4 nested loops are allowed.
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void bloop(const UDSPInstruction opc)
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{
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u16 reg = opc & 0x1f;
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u16 cnt = g_dsp.r[reg];
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u16 loop_pc = dsp_fetch_code();
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if (cnt)
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{
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dsp_reg_store_stack(0, g_dsp.pc);
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dsp_reg_store_stack(2, loop_pc);
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dsp_reg_store_stack(3, cnt);
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}
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else
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{
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g_dsp.pc = loop_pc;
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dsp_skip_inst();
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}
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}
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// BLOOPI #I, addrA
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// 0001 0001 iiii iiii
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// aaaa aaaa aaaa aaaa
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// Repeatedly execute block of code starting at following opcode until
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// counter specified by immediate value I reaches zero. Block ends at specified
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// address addrA inclusive, ie. opcode at addrA is the last opcode included in
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// loop. Counter is pushed on loop stack $st3, end of block address is pushed
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// on loop stack $st2 and repeat address is pushed on call stack $st0. Up to 4
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// nested loops are allowed.
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void bloopi(const UDSPInstruction opc)
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{
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u16 cnt = opc & 0xff;
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u16 loop_pc = dsp_fetch_code();
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if (cnt)
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{
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dsp_reg_store_stack(0, g_dsp.pc);
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dsp_reg_store_stack(2, loop_pc);
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dsp_reg_store_stack(3, cnt);
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}
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else
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{
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g_dsp.pc = loop_pc;
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dsp_skip_inst();
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}
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}
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} // namespace
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