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cgen.c
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cgen.c
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/****************************************************/
/* File: cgen.c */
/* The code generator implementation */
/* for the TINY compiler */
/* (generates code for the TM machine) */
/* Compiler Construction: Principles and Practice */
/* Kenneth C. Louden */
/****************************************************/
#include "globals.h"
#include "symtab.h"
#include "code.h"
#include "cgen.h"
/* tmpOffset is the memory offset for temps
It is decremented each time a temp is
stored, and incremented when loaded again
*/
static int tmpOffset = 0;
/* prototype for internal recursive code generator */
static void cGen (TreeNode * tree);
/* Procedure genStmt generates code at a statement node */
static void genStmt( TreeNode * tree)
{ TreeNode * p1, * p2, * p3, *curCase;
int savedLoc1,savedLoc2,currentLoc, jmpToNextLoc, lastPos;
int loc;
switch (tree->kind.stmt) {
case SwitchK :
if (TraceCode) emitComment("-> switch") ;
p1 = tree->child[0] ;
p2 = tree->child[1] ;
//get the variable
cGen(p1);
//generate Cases
cGen(p2);
break; /* switch_k */
case CaseK:
curCase = tree;
if (TraceCode) emitComment("-> ") ;
emitRM("LDA", ac1, 0, ac,"trying to put ac value on ac1");
do{
p1 = curCase->child[0] ;
p2 = curCase->child[1] ;
/* get constant */
cGen(p1);
emitRO("SUB",ac,ac1,ac,"op ==") ;//subtrai AC de AC1
emitRM("JEQ",ac,1,pc,"br if true");//PULA O PROXIMO COMANDO SE O RESULTADO FOR 0
jmpToNextLoc = emitSkip(1);//pula 1 linha pra deixar espaço pro jmp que leva pro proximo case
cGen(p2);//gera os statements
lastPos = emitSkip(0);//salva ultima posição
emitBackup(jmpToNextLoc);//volta pra local do jmp pro proximo case
emitRM("LDA",pc,(lastPos - jmpToNextLoc),pc,"unconditional jmp");//pula pra posição do proximo case
emitRestore();
curCase = curCase->sibling;
}while(curCase!=NULL);
break; /* switch_k */
case IfK :
if (TraceCode) emitComment("-> if") ;
p1 = tree->child[0] ;
p2 = tree->child[1] ;
p3 = tree->child[2] ;
/* generate code for test expression */
cGen(p1);
savedLoc1 = emitSkip(1) ;
emitComment("if: jump to else belongs here");
/* recurse on then part */
cGen(p2);
savedLoc2 = emitSkip(1) ;
emitComment("if: jump to end belongs here");
currentLoc = emitSkip(0) ;
emitBackup(savedLoc1) ;
emitRM_Abs("JEQ",ac,currentLoc,"if: jmp to else");
emitRestore() ;
/* recurse on else part */
cGen(p3);
currentLoc = emitSkip(0) ;
emitBackup(savedLoc2) ;
emitRM_Abs("LDA",pc,currentLoc,"jmp to end") ;
emitRestore() ;
if (TraceCode) emitComment("<- if") ;
break; /* if_k */
case WhileK:
printf("++++++++++While statement identified+++++++++++++++.\n");
if (TraceCode)
emitComment("-> while");
p1 = tree->child[0];
p2 = tree->child[1];
currentLoc = emitSkip(0);
cGen(p1);
savedLoc1 = emitSkip(1);
cGen(p2);
emitRM_Abs("LDA", pc, currentLoc, "jmp to test");
currentLoc = emitSkip(0);
emitBackup(savedLoc1);
emitRM_Abs("JEQ", ac, currentLoc, "skip the body");
emitRestore();
if (TraceCode)
emitComment("<- while");
break;
case RepeatK:
if (TraceCode) emitComment("-> repeat") ;
p1 = tree->child[0] ;
p2 = tree->child[1] ;
savedLoc1 = emitSkip(0);
emitComment("repeat: jump after body comes back here");
/* generate code for body */
cGen(p1);
/* generate code for test */
cGen(p2);
emitRM_Abs("JEQ",ac,savedLoc1,"repeat: jmp back to body");
if (TraceCode) emitComment("<- repeat") ;
break; /* repeat */
case AssignK:
if (TraceCode) emitComment("-> assign") ;
/* generate code for rhs */
cGen(tree->child[0]);
/* now store value */
loc = st_lookup(tree->attr.name);
emitRM("ST",ac,loc,gp,"assign: store value");
if (TraceCode) emitComment("<- assign") ;
break; /* assign_k */
case ReadK:
emitRO("IN",ac,0,0,"read integer value");
loc = st_lookup(tree->attr.name);
emitRM("ST",ac,loc,gp,"read: store value");
break;
case WriteK:
/* generate code for expression to write */
cGen(tree->child[0]);
/* now output it */
emitRO("OUT",ac,0,0,"write ac");
break;
default:
break;
}
} /* genStmt */
/* Procedure genExp generates code at an expression node */
static void genExp( TreeNode * tree)
{ int loc;
TreeNode * p1, * p2;
switch (tree->kind.exp) {
case ConstK :
if (TraceCode) emitComment("-> Const") ;
/* gen code to load integer constant using LDC */
emitRM("LDC",ac,tree->attr.val,0,"load const");
if (TraceCode) emitComment("<- Const") ;
break; /* ConstK */
case IdK :
if (TraceCode) emitComment("-> Id") ;
loc = st_lookup(tree->attr.name);
emitRM("LD",ac,loc,gp,"load id value");
if (TraceCode) emitComment("<- Id") ;
break; /* IdK */
case OpK :
if (TraceCode) emitComment("-> Op") ;
p1 = tree->child[0];
p2 = tree->child[1];
/* gen code for ac = left arg */
cGen(p1);
/* gen code to push left operand */
emitRM("ST",ac,tmpOffset--,mp,"op: push left");
/* gen code for ac = right operand */
cGen(p2);
/* now load left operand */
emitRM("LD",ac1,++tmpOffset,mp,"op: load left");
switch (tree->attr.op) {
case PLUS :
emitRO("ADD",ac,ac1,ac,"op +");
break;
case MINUS :
emitRO("SUB",ac,ac1,ac,"op -");
break;
case TIMES :
emitRO("MUL",ac,ac1,ac,"op *");
break;
case OVER :
emitRO("DIV",ac,ac1,ac,"op /");
break;
case LT :
emitRO("SUB",ac,ac1,ac,"op <") ;
emitRM("JLT",ac,2,pc,"br if true") ;
emitRM("LDC",ac,0,ac,"false case") ;
emitRM("LDA",pc,1,pc,"unconditional jmp") ;
emitRM("LDC",ac,1,ac,"true case") ;
break;
case EQ :
emitRO("SUB",ac,ac1,ac,"op ==") ;
emitRM("JEQ",ac,2,pc,"br if true");
emitRM("LDC",ac,0,ac,"false case") ;
emitRM("LDA",pc,1,pc,"unconditional jmp") ;
emitRM("LDC",ac,1,ac,"true case") ;
break;
default:
emitComment("BUG: Unknown operator");
break;
} /* case op */
if (TraceCode) emitComment("<- Op") ;
break; /* OpK */
default:
break;
}
} /* genExp */
/* Procedure cGen recursively generates code by
* tree traversal
*/
static void cGen( TreeNode * tree)
{ if (tree != NULL)
{ switch (tree->nodekind) {
case StmtK:
genStmt(tree);
break;
case ExpK:
genExp(tree);
break;
default:
break;
}
cGen(tree->sibling);
}
}
/**********************************************/
/* the primary function of the code generator */
/**********************************************/
/* Procedure codeGen generates code to a code
* file by traversal of the syntax tree. The
* second parameter (codefile) is the file name
* of the code file, and is used to print the
* file name as a comment in the code file
*/
void codeGen(TreeNode * syntaxTree, char * codefile)
{ char * s = malloc(strlen(codefile)+7);
strcpy(s,"File: ");
strcat(s,codefile);
emitComment("TINY Compilation to TM Code");
emitComment(s);
/* generate standard prelude */
emitComment("Standard prelude:");
emitRM("LD",mp,0,ac,"load maxaddress from location 0");
emitRM("ST",ac,0,ac,"clear location 0");
emitComment("End of standard prelude.");
/* generate code for TINY program */
cGen(syntaxTree);
/* finish */
emitComment("End of execution.");
emitRO("HALT",0,0,0,"");
}