// the classic back patch using the emit functions
int backPatchJumpToHere(int addr, char *comment)
{
int currloc;
currloc = emitSkip(0);
emitBackup(addr);
emitRMAbs((char *)"LDA", PC, currloc, comment);
emitBackup(currloc);
}
/* Procedure genStmt generates code at a statement node */
static void genStmt( TreeNode * tree)
{ TreeNode * p1, * p2, * p3;
int savedLoc1,savedLoc2,currentLoc;
int loc;
switch (tree->kind.stmt) {
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 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 */