oparith.cpp

motorola ezx 平台下的fba模拟器

#include "app.h"

// --------------------- Opcodes 0x0000+ ---------------------
// Emit an Ori/And/Sub/Add/Eor/Cmp Immediate opcode, 0000ttt0 ssaaaaaa
int OpArith(int op)
{
  int type=0,size=0;
  int sea=0,tea=0;
  int use=0;

  // Get source and target EA
  type=(op>>9)&7; if (type==4 || type>=7) return 1;
  size=(op>>6)&3; if (size>=3) return 1;
  sea=   0x003c;
  tea=op&0x003f;

  // See if we can do this opcode:
  if (EaCanRead(tea,size)==0) return 1;
  if (EaCanWrite(tea)==0 || EaAn(tea)) return 1;

  use=OpBase(op);
  if (op!=use) { OpUse(op,use); return 0; } // Use existing handler

  OpStart(op); Cycles=4;

  EaCalc(10,0x0000, sea,size,1);
  EaRead(10,    10, sea,size,0,1);

  EaCalc(11,0x003f, tea,size,1);
  EaRead(11,     0, tea,size,0x003f,1);

  ot(";@ Do arithmetic:\n");

  if (type==0) ot("  orr r1,r0,r10\n");
  if (type==1) ot("  and r1,r0,r10\n");
  if (type==2) ot("  subs r1,r0,r10 ;@ Defines NZCV\n");
  if (type==3) ot("  adds r1,r0,r10 ;@ Defines NZCV\n");
  if (type==5) ot("  eor r1,r0,r10\n");
  if (type==6) ot("  cmp r0,r10 ;@ Defines NZCV\n");

  if (type<2 || type==5) ot("  adds r1,r1,#0 ;@ Defines NZ, clears CV\n"); // 0,1,5

  if (type< 2) OpGetFlags(0,0); // Ori/And
  if (type==2) OpGetFlags(1,1); // Sub: Subtract/X-bit
  if (type==3) OpGetFlags(0,1); // Add: X-bit
  if (type==5) OpGetFlags(0,0); // Eor
  if (type==6) OpGetFlags(1,0); // Cmp: Subtract
  ot("\n");

  if (type!=6)
  {
    EaWrite(11, 1, tea,size,0x003f,1);
  }

  // Correct cycles:
  if (type==6)
  {
    if (size>=2 && tea<0x10) Cycles+=2;
  }
  else
  {
    if (size>=2) Cycles+=4;
    if (tea>=8)  Cycles+=4;
    if (type==1 && size>=2 && tea<8) Cycles-=2;
  }

  OpEnd();

  return 0;
}

// --------------------- Opcodes 0x5000+ ---------------------
int OpAddq(int op)
{
  // 0101nnnt xxeeeeee (nnn=#8,1-7 t=addq/subq xx=size, eeeeee=EA)
  int num=0,type=0,size=0,ea=0;
  int use=0;
  char count[16]="";
  int shift=0;

  num =(op>>9)&7; if (num==0) num=8;
  type=(op>>8)&1;
  size=(op>>6)&3; if (size>=3) return 1;
  ea  = op&0x3f;

  // See if we can do this opcode:
  if (EaCanRead (ea,size)==0) return 1;
  if (EaCanWrite(ea)     ==0) return 1;
  if (size == 0 && EaAn(ea) ) return 1;

  use=OpBase(op,1);

  if (num!=8) use|=0x0e00; // If num is not 8, use same handler
  if (op!=use) { OpUse(op,use); return 0; } // Use existing handler

  OpStart(op);
  Cycles=ea<8?4:8;
  if(type==0&&size==1) Cycles=ea<0x10?4:8;
  if(size>=2) Cycles=ea<0x10?8:12;

  if (size>0 && (ea&0x38)==0x08) size=2; // addq.w #n,An is also 32-bit

  EaCalc(10,0x003f, ea,size,1);
  EaRead(10,     0, ea,size,0x003f,1);

  shift=32-(8<<size);

  if (num!=8)
  {
    int lsr=9-shift;

    if (lsr>=0) ot("  mov r2,r8,lsr #%d ;@ Get quick value\n", lsr);
    else        ot("  mov r2,r8,lsl #%d ;@ Get quick value\n",-lsr);

    ot("  and r2,r2,#0x%.4x\n",7<<shift);
    ot("\n");
    strcpy(count,"r2");
  }

  if (num==8) sprintf(count,"#0x%.4x",8<<shift);

  if (type==0) ot("  adds r1,r0,%s\n",count);
  if (type==1) ot("  subs r1,r0,%s\n",count);

  if ((ea&0x38)!=0x08) OpGetFlags(type,1);
  ot("\n");

  EaWrite(10,     1, ea,size,0x003f,1);

  OpEnd();

  return 0;
}

// --------------------- Opcodes 0x8000+ ---------------------
// 1t0tnnnd xxeeeeee (tt=type:or/sub/and/add xx=size, eeeeee=EA)
int OpArithReg(int op)
{
  int use=0;
  int type=0,size=0,dir=0,rea=0,ea=0;

  type=(op>>12)&5;
  rea =(op>> 9)&7;
  dir =(op>> 8)&1; // er,re
  size=(op>> 6)&3; if (size>=3) return 1;
  ea  = op&0x3f;

  if (dir && ea<0x10) return 1; // addx/subx opcode

  // See if we can do this opcode:
  if (dir==0 && EaCanRead (ea,size)==0) return 1;
  if (dir    && EaCanWrite(ea)==0)      return 1;
  if ((size==0||!(type&1))&&EaAn(ea))   return 1;

  use=OpBase(op);
  use&=~0x0e00; // Use same opcode for Dn
  if (op!=use) { OpUse(op,use); return 0; } // Use existing handler

  OpStart(op); Cycles=4;

  ot(";@ Get r10=EA r11=EA value\n");
  EaCalc(10,0x003f, ea,size,1);
  EaRead(10,    11, ea,size,0x003f,1);
  ot(";@ Get r0=Register r1=Register value\n");
  EaCalc( 0,0x0e00,rea,size,1);
  EaRead( 0,     1,rea,size,0x0e00,1);

  ot(";@ Do arithmetic:\n");
  if (type==0) ot("  orr  ");
  if (type==1) ot("  subs ");
  if (type==4) ot("  and  ");
  if (type==5) ot("  adds ");
  if (dir) ot("r1,r11,r1\n");
  else     ot("r1,r1,r11\n");

  if ((type&1)==0) ot("  adds r1,r1,#0 ;@ Defines NZ, clears CV\n");

  OpGetFlags(type==1,type&1); // 1==subtract
  ot("\n");

  ot(";@ Save result:\n");
  if (dir) EaWrite(10, 1, ea,size,0x003f,1);
  else     EaWrite( 0, 1,rea,size,0x0e00,1);

  if(rea==ea) {
    if(ea<8) Cycles=(size>=2)?8:4; else Cycles+=(size>=2)?26:14;
  } else if(dir) {
    Cycles+=4;
    if(size>=2) Cycles+=4;
  } else {
    if(size>=2) {
	  Cycles+=2;
	  if(ea<0x10||ea==0x3c) Cycles+=2;
	}
  }

  OpEnd();

  return 0;
}

// --------------------- Opcodes 0x80c0+ ---------------------
int OpMul(int op)
{
  // Div/Mul: 1m00nnns 11eeeeee (m=Mul, nnn=Register Dn, s=signed, eeeeee=EA)
  int type=0,rea=0,sign=0,ea=0;
  int use=0;

  type=(op>>14)&1; // div/mul
  rea =(op>> 9)&7;
  sign=(op>> 8)&1;
  ea  = op&0x3f;

  // See if we can do this opcode:
  if (EaCanRead(ea,1)==0||EaAn(ea)) return 1;

  use=OpBase(op);
  use&=~0x0e00; // Use same for all registers
  if (op!=use) { OpUse(op,use); return 0; } // Use existing handler

  OpStart(op);
  if(type) Cycles=54;
  else     Cycles=sign?158:140;

  EaCalc(10,0x003f, ea, 1);
  EaRead(10,    10, ea, 1,0x003f);

  EaCalc (0,0x0e00,rea, 2,1);
  EaRead (0,     2,rea, 2,0x0e00,1);

  if (type==0) // div
  {
    // the manual says C is always cleared, but neither Musashi nor FAME do that
    //ot("  bic r9,r9,#0x20000000 ;@ always clear C\n");
    ot("  tst r10,r10\n");
    ot("  beq divzero%.4x ;@ division by zero\n",op);
    ot("\n");
    
    if (sign)
    {
      ot("  mov r11,#0 ;@ r11 = 1 or 2 if the result is negative\n");
      ot("  orrmi r11,r11,#1\n");
      ot("  rsbmi r10,r10,#0 ;@ Make r10 positive\n");
      ot("\n");
      ot("  tst r2,r2\n");
      ot("  orrmi r11,r11,#2\n");
      ot("  rsbmi r2,r2,#0 ;@ Make r2 positive\n");
      ot("\n");
    }
    else
	{
      ot("  mov r10,r10,lsl #16 ;@ use only 16 bits of divisor\n");
      ot("  mov r10,r10,lsr #16\n");
	}

    ot(";@ Divide r2 by r10\n");
    ot("  mov r3,#0\n");
    ot("  mov r1,r10\n");
    ot("\n");
    ot(";@ Shift up divisor till it's just less than numerator\n");
    ot("Shift%.4x%s\n",op,ms?"":":");
    ot("  cmp r1,r2,lsr #1\n");
    ot("  movls r1,r1,lsl #1\n");
    ot("  bcc Shift%.4x\n",op);
    ot("\n");

    ot("Divide%.4x%s\n",op,ms?"":":");
    ot("  cmp r2,r1\n");
    ot("  adc r3,r3,r3 ;@ Double r3 and add 1 if carry set\n");
    ot("  subcs r2,r2,r1\n");
    ot("  teq r1,r10\n");
    ot("  movne r1,r1,lsr #1\n");
    ot("  bne Divide%.4x\n",op);
    ot("\n");
    ot(";@r3==quotient,r2==remainder\n");

    if (sign)
    {
	  // sign correction
      ot("  and r1,r11,#1\n");
      ot("  teq r1,r11,lsr #1\n");
      ot("  rsbne r3,r3,#0 ;@ negate if quotient is negative\n");
      ot("  tst r11,#2\n");
      ot("  rsbne r2,r2,#0 ;@ negate the remainder if divident was negative\n");
      ot("\n");

	  // signed overflow check
	  ot("  mov r1,r3,asl #16\n");
	  ot("  cmp r3,r1,asr #16 ;@ signed overflow?\n");
      ot("  orrne r9,r9,#0x10000000 ;@ set overflow flag\n");
      ot("  bne endofop%.4x ;@ overflow!\n",op);
    }
	else
	{
	  // overflow check
	  ot("  movs r1,r3,lsr #16 ;@ check for overflow condition\n");
      ot("  orrne r9,r9,#0x10000000 ;@ set overflow flag\n");
      ot("  bne endofop%.4x ;@ overflow!\n",op);
	}

    ot("  mov r1,r3,lsl #16 ;@ Clip to 16-bits\n");
    ot("  adds r1,r1,#0 ;@ Defines NZ, clears CV\n");
    OpGetFlags(0,0);

    ot("  mov r1,r1,lsr #16\n");
    ot("  orr r1,r1,r2,lsl #16 ;@ Insert remainder\n");
  }

  if (type==1)
  {
    char *shift="asr";

    ot(";@ Get 16-bit signs right:\n");
    if (sign==0) { ot("  mov r10,r10,lsl #16\n"); shift="lsr"; }
    ot("  mov r2,r2,lsl #16\n");

    if (sign==0) ot("  mov r10,r10,lsr #16\n");
    ot("  mov r2,r2,%s #16\n",shift);
    ot("\n");

    ot("  mul r1,r2,r10\n");
    ot("  adds r1,r1,#0 ;@ Defines NZ, clears CV\n");
    OpGetFlags(0,0);
  }
  ot("\n");

  EaWrite(0,     1,rea, 2,0x0e00,1);

  ot("endofop%.4x%s\n",op,ms?"":":");
  OpEnd();

  ot("divzero%.4x%s\n",op,ms?"":":");
  ot("  mov r0,#0x14 ;@ Divide by zero\n");
  ot("  bl Exception\n");
  Cycles+=38;
  OpEnd();
  ot("\n");

  return 0;
}

// Get X Bit into carry - trashes r2
int GetXBit(int subtract)
{
  ot(";@ Get X bit:\n");
  ot("  ldrb r2,[r7,#0x45]\n");
  if (subtract) ot("  mvn r2,r2,lsl #28 ;@ Invert it\n");
  else          ot("  mov r2,r2,lsl #28\n");
  ot("  msr cpsr_flg,r2 ;@ Get into Carry\n");
  ot("\n");
  return 0;
}

// --------------------- Opcodes 0x8100+ ---------------------
// 1t00ddd1 0000asss - sbcd/abcd Ds,Dd or -(As),-(Ad)
int OpAbcd(int op)
{
  int use=0;
  int type=0,sea=0,addr=0,dea=0;
  
  type=(op>>14)&1; // sbcd/abcd
  dea =(op>> 9)&7;
  addr=(op>> 3)&1;
  sea = op     &7;

  if (addr) { sea|=0x20; dea|=0x20; }

  use=op&~0x0e07; // Use same opcode for all registers..
  if (sea==0x27||dea==0x27) use=op; // ..except -(a7)
  if (op!=use) { OpUse(op,use); return 0; } // Use existing handler

  OpStart(op); Cycles=6;

  EaCalc( 0,0x0007, sea,0,1);
  EaRead( 0,    10, sea,0,0x0007,1);
  EaCalc(11,0x0e00, dea,0,1);
  EaRead(11,     1, dea,0,0x0e00,1);

  ot("  bic r9,r9,#0xb1000000 ;@ clear all flags except old Z\n");