ctrump/ast/fold.c

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/* -*- coding:utf-8 -*- 
 Copyright (c) 2009, Fixstars Corporation
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification, 
 are permitted provided that the following conditions are met:
 
   * Redistributions of source code must retain the above copyright notice,
     this list of conditions and the following disclaimer.
 
   * Redistributions in binary form must reproduce the above copyright notice,
     this list of conditions and the following disclaimer in the documentation
     and/or other materials provided with the distribution.
 
   * Neither the name of Fixstars Corporation nor the names of its contributors
     may be used to endorse or promote products derived from this software
     without specific prior written permission.
 
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "ctrump/ast/ast.h"
#include <stdlib.h>

int
ctrump_ast_fold_const_sint(const struct ctrump_expr *expr, int *is_const)
{
tailcall:
    switch (expr->code) {
    case CTRUMP_EXPR_SINT_LITERAL:
        *is_const = 1;
        return expr->u.sint_literal.value;

    case CTRUMP_EXPR_PAREN:
        expr = expr->u.paren.expr;
        goto tailcall;

    default:
        /* unimplemented */
        *is_const = 0;
        break;
    }

    return 0;
}

void
ctrump_ast_fold_const_offset_sint(int *ret_offset, struct ctrump_expr **ret_expr,
                                  struct ctrump_expr *e)
{
    int is_const;
    int val;
    struct ctrump_expr *lhs, *rhs;

    *ret_offset = 0;

tailcall:
    switch (e->code) {
    case CTRUMP_EXPR_SINT_LITERAL:
        *ret_expr = NULL;
        *ret_offset = e->u.sint_literal.value;
        return;

    case CTRUMP_EXPR_BIN_ADD:
    case CTRUMP_EXPR_BIN_SUB:
        lhs = e->u.binary.lhs;
        rhs = e->u.binary.rhs;

        val = ctrump_ast_fold_const_sint(lhs, &is_const);
        if (is_const) {
            if (e->code == CTRUMP_EXPR_BIN_ADD) {
                *ret_offset += val;
            } else {
                *ret_offset -= val;
            }
            e = rhs;
            goto tailcall;
        } else {
            val = ctrump_ast_fold_const_sint(rhs, &is_const);
            if (is_const) {
                if (e->code == CTRUMP_EXPR_BIN_ADD) {
                    *ret_offset += val;
                } else {
                    *ret_offset -= val;
                }
                e = lhs;
                goto tailcall;
            } else {
                *ret_expr = e;
                return;
            }
        }
        break;

    case CTRUMP_EXPR_PAREN:
        e = e->u.paren.expr;
        goto tailcall;

    default:
        break;
    }

    *ret_expr = e;
}

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