Expression Parsing and Evaluation in CS 5300 - SJAllan's Compiler - Prof. Stephen J. Allan, Study notes of Computer Science

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Expressions

CS 5300 - SJAllan 2

Expression Structure

typedef enum expr_kind EX_KIND; enum expr_kind {GlobalV, LocalV, LocalA, Cons, RegisterV, RegisterA, FuncRef};

typedef struct expr_info EXPR;

struct expr_info { TYPE *ex_type; EX_KIND ex_kind; int ex_inv; EXPR ex_next; }; / expr_info */

CS 5300 - SJAllan 4

Code for makeexpr

EXPR *makeexpr (ID *st_ptr) { TYPE type; EX_KIND kind; int inv; type = st_ptr->id_type; inv = st_ptr->id_addr; if (st_ptr->id_level == GLOBALSCOPE) kind = GlobalV; else if (st_ptr->id_level == currscope) if (st_ptr->id_kind == RParameter) kind = LocalA; else kind = LocalV; else kind = LocalV; return(newexpr(type, kind, inv)); } / makeexpr */

CS 5300 - SJAllan 5

Constant Expression

Expression :... | INTCONSTSY {$$ = newexpr(int_type, Cons, $1);} | CHARCONSTSY {$$ = newexpr(char_type, Cons, $1);} | STRINGCONSTSY {$$ = strexpr($1);}

... ;

CS 5300 - SJAllan 7

LValue

LValue :... | IDENTSY {$$ = lvalue($1);} ;

CS 5300 - SJAllan 8

Binary Operators

Expression :... | Expression ADDSY Expression {$$ = binop($1, AddOp, $3);} | Expression SUBSY Expression {$$ = binop($1, SubOp, $3);} | Expression MULSY Expression {$$ = binop($1, MulOp, $3);} | Expression DIVSY Expression {$$ = binop($1, DivOp, $3);} | Expression MODSY Expression {$$ = binop($1, ModOp, $3);}

... ;

CS 5300 - SJAllan 10

Unary Minus

Expression :... | SUBSY Expression %prec UNMINUSSY {$$ = unop(SubOp, $2);}

... ;

CS 5300 - SJAllan 11

MIPS Code for Comparison

s? DEST, S1, S