root/ext/opcache/Optimizer/nop_removal.c

DEFINITIONS

1. nop_removal

/* pass 10:
 * - remove NOPs
 */

static void nop_removal(zend_op_array *op_array)
{
        zend_op *end, *opline;
        zend_uint new_count, i, shift;
        int j;
        zend_uint *shiftlist;
        ALLOCA_FLAG(use_heap);

        shiftlist = (zend_uint *)DO_ALLOCA(sizeof(zend_uint) * op_array->last);
        i = new_count = shift = 0;
        end = op_array->opcodes + op_array->last;
        for (opline = op_array->opcodes; opline < end; opline++) {

#if ZEND_EXTENSION_API_NO >= PHP_5_3_X_API_NO
                /* GOTO target is unresolved yet. We can't optimize. */
                if (opline->opcode == ZEND_GOTO &&
                        Z_TYPE(ZEND_OP2_LITERAL(opline)) != IS_LONG) {
                        /* TODO: in general we can avoid this restriction */
                        FREE_ALLOCA(shiftlist);
                        return;
                }
#endif

                /* Kill JMP-over-NOP-s */
                if (opline->opcode == ZEND_JMP && ZEND_OP1(opline).opline_num > i) {
                        /* check if there are only NOPs under the branch */
                        zend_op *target = op_array->opcodes + ZEND_OP1(opline).opline_num - 1;

                        while (target->opcode == ZEND_NOP) {
                                target--;
                        }
                        if (target == opline) {
                                /* only NOPs */
                                opline->opcode = ZEND_NOP;
                        }
                }

                shiftlist[i++] = shift;
                if (opline->opcode == ZEND_NOP) {
                        shift++;
                } else {
                        if (shift) {
                                op_array->opcodes[new_count] = *opline;
                        }
                        new_count++;
                }
        }

        if (shift) {
                op_array->last = new_count;
                end = op_array->opcodes + op_array->last;

                /* update JMPs */
                for (opline = op_array->opcodes; opline<end; opline++) {
                        switch (opline->opcode) {
                                case ZEND_JMP:
#if ZEND_EXTENSION_API_NO >= PHP_5_3_X_API_NO
                                case ZEND_GOTO:
#endif
#if ZEND_EXTENSION_API_NO > PHP_5_4_X_API_NO
                                case ZEND_FAST_CALL:
#endif
                                        ZEND_OP1(opline).opline_num -= shiftlist[ZEND_OP1(opline).opline_num];
                                        break;
                                case ZEND_JMPZ:
                                case ZEND_JMPNZ:
                                case ZEND_JMPZ_EX:
                                case ZEND_JMPNZ_EX:
                                case ZEND_FE_FETCH:
                                case ZEND_FE_RESET:
                                case ZEND_NEW:
#if ZEND_EXTENSION_API_NO >= PHP_5_3_X_API_NO
                                case ZEND_JMP_SET:
#endif
#if ZEND_EXTENSION_API_NO > PHP_5_3_X_API_NO
                                case ZEND_JMP_SET_VAR:
#endif
                                        ZEND_OP2(opline).opline_num -= shiftlist[ZEND_OP2(opline).opline_num];
                                        break;
                                case ZEND_JMPZNZ:
                                        ZEND_OP2(opline).opline_num -= shiftlist[ZEND_OP2(opline).opline_num];
                                        opline->extended_value -= shiftlist[opline->extended_value];
                                        break;
                                case ZEND_CATCH:
                                        opline->extended_value -= shiftlist[opline->extended_value];
                                        break;
                        }
                }

                /* update brk/cont array */
                for (j = 0; j < op_array->last_brk_cont; j++) {
                        op_array->brk_cont_array[j].brk -= shiftlist[op_array->brk_cont_array[j].brk];
                        op_array->brk_cont_array[j].cont -= shiftlist[op_array->brk_cont_array[j].cont];
                        op_array->brk_cont_array[j].start -= shiftlist[op_array->brk_cont_array[j].start];
                }

                /* update try/catch array */
                for (j = 0; j < op_array->last_try_catch; j++) {
                        op_array->try_catch_array[j].try_op -= shiftlist[op_array->try_catch_array[j].try_op];
                        op_array->try_catch_array[j].catch_op -= shiftlist[op_array->try_catch_array[j].catch_op];
#if ZEND_EXTENSION_API_NO > PHP_5_4_X_API_NO
                        if (op_array->try_catch_array[j].finally_op) {
                                op_array->try_catch_array[j].finally_op -= shiftlist[op_array->try_catch_array[j].finally_op];
                                op_array->try_catch_array[j].finally_end -= shiftlist[op_array->try_catch_array[j].finally_end];
                        }
#endif
                }

#if ZEND_EXTENSION_API_NO >= PHP_5_3_X_API_NO
                /* update early binding list */
                if (op_array->early_binding != (zend_uint)-1) {
                        zend_uint *opline_num = &op_array->early_binding;

                        do {
                                *opline_num -= shiftlist[*opline_num];
                                opline_num = &ZEND_RESULT(&op_array->opcodes[*opline_num]).opline_num;
                        } while (*opline_num != (zend_uint)-1);
                }
#endif
        }
        FREE_ALLOCA(shiftlist);
}