CodeGen.c

#include <stdlib.h>
#include <stdio.h>
#include <strings.h>
#include <string.h>

#include "CodeGen.h"

extern FILE *aFile;

int NextLabel = 1;
int NextWord = 1;

struct TmpReg
{
  unsigned char Free;
  unsigned char Used;
  char *Name;
} Registers[10] = {{1, 0, "$t0"}, {1, 0, "$t1"}, {1, 0, "$t2"}, {1, 0, "$t3"}, {1, 0, "$t4"}, {1, 0, "$t5"}, {1, 0, "$t6"}, {1, 0, "$t7"}, {1, 0, "$t8"}, {1, 0, "$t9"}};
#define MAXREG 10

char Buf[16];

char *
CopyStr(char *AStr)
{
  return (AStr) ? strdup(AStr) : NULL;
}

struct InstrSeq *
GenInstr(char *Label, char *OpCode, char *Oprnd1, char *Oprnd2, char *Oprnd3)
{
  struct InstrSeq *instr;

  instr = (struct InstrSeq *)malloc(sizeof(struct InstrSeq));
  instr->Label = CopyStr(Label);
  instr->OpCode = CopyStr(OpCode);
  instr->Oprnd1 = CopyStr(Oprnd1);
  instr->Oprnd2 = CopyStr(Oprnd2);
  instr->Oprnd3 = CopyStr(Oprnd3);
  instr->Next = NULL;

  return instr;
}

extern struct InstrSeq *
AppendSeq(struct InstrSeq *Seq1, struct InstrSeq *Seq2)
{
  struct InstrSeq *instr;

  if (!Seq1)
    return Seq2;

  instr = Seq1;
  while (instr->Next)
    instr = instr->Next;
  instr->Next = Seq2;

  return Seq1;
}

void WriteSeq(struct InstrSeq *ASeq)
{
  struct InstrSeq *instr;

  printf("WriteSeq\n");
  instr = ASeq;
  while (instr)
  {
    if (instr->Label)
      fprintf(aFile, "%s:", instr->Label);
    if (instr->OpCode)
    {
      fprintf(aFile, "\t%s\t", instr->OpCode);
      if (instr->Oprnd1)
        fprintf(aFile, "\t%s", instr->Oprnd1);
      if (instr->Oprnd2)
        fprintf(aFile, ", %s", instr->Oprnd2);
      if (instr->Oprnd3)
        fprintf(aFile, ", %s", instr->Oprnd3);
    }
    fprintf(aFile, "\n");
    instr = instr->Next;
  }
  if (aFile != stdout)
    fclose(aFile);
}

char *
GenLabel()
{
  char *label;

  label = (char *)malloc(8);
  sprintf(label, "L%d", NextLabel++);

  return label;
}

char *GenWord()
{
  char *word;

  word = (char *)malloc(8);
  sprintf(word, "_W%d", NextWord++);

  return word;
}

int AvailTmpReg()
{
  int i;

  for (i = 0; i < MAXREG; i++)
  {
    if (Registers[i].Free)
    {
      Registers[i].Free = 0;
      Registers[i].Used = 1;
      return i;
    }
  }

  return -1;
}

char *
TmpRegName(int RegNum)
{
  if ((RegNum >= 0) && (RegNum < MAXREG))
  {
    return Registers[RegNum].Name;
  }
  else
  {
    return NULL;
  }
}

void ReleaseTmpReg(int ANum)
{
  if ((ANum >= 0) && (ANum < MAXREG))
  {
    Registers[ANum].Free = 1;
  }
  return;
}

void ResetAllTmpReg()
{
  int i;

  for (i = 0; i < MAXREG; i++)
  {
    Registers[i].Free = 1;
    Registers[i].Used = 0;
  }

  return;
}

struct InstrSeq *
SaveSeq()
{
  struct InstrSeq *save, *code;
  int i, scnt;
  char addr[8], offset[8];

  scnt = 0;
  save = NULL;
  code = NULL;
  for (i = 0; i < MAXREG; i++)
  {
    if (!Registers[i].Free)
    {
      scnt++;
      sprintf(addr, "%d($sp)", scnt * 4);
      save = AppendSeq(save, GenInstr(NULL, "sw", TmpRegName(i), addr, NULL));
    }
  }
  if (scnt > 0)
  {
    sprintf(offset, "%d", scnt * 4);
    code = GenInstr(NULL, "subu", "$sp", "$sp", offset);
    AppendSeq(code, save);
  }

  return code;
}

struct InstrSeq *
RestoreSeq()
{
  struct InstrSeq *code, *save;
  int i, scnt;

  char addr[8], offset[8];

  scnt = 0;
  save = NULL;
  code = NULL;
  for (i = 0; i < MAXREG; i++)
  {
    if (!Registers[i].Free)
    {
      scnt++;
      sprintf(addr, "%d($sp)", scnt * 4);
      save = AppendSeq(save, GenInstr(NULL, "lw", TmpRegName(i), addr, NULL));
    }
  }
  if (scnt > 0)
  {
    sprintf(offset, "%d", scnt * 4);
    code = AppendSeq(save, GenInstr(NULL, "addu", "$sp", "$sp", offset));
  }

  return code;
}

char *
Imm(int Val)
{
  sprintf(Buf, "%d", Val);
  return Buf;
}

char *
RegOff(int Offset, char *Reg)
{
  sprintf(Buf, "%d(%s)", Offset, Reg);
  return Buf;
}