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view lwasm/insn_rel.c @ 434:052c5f335a92
Fix bug in like terms collection in expression simplification
Like term collection would lose the actual "variable" part of the term if
the second term collected happened to have no coefficient. This would cause
the expression to take the value of the calculated coefficient which is
obviously wrong.
Thanks to hider <stego@satx.rr.com> for reporting the bug and providing a
proper test case.
Observation: this bug has been present since the first pre-release of
lwtools 3.0 when the algebraic expression system was introduced. Apparently
people tend not to create expressions that trigger the like terms handler.
The specific conditions require the symbol to be undefined and the second
operand to the addition has to have no coefficient so it's likely a fairly
rare scenario. Still, it is somewhat surprising that nobody tripped on it
before now.
author | William Astle <lost@l-w.ca> |
---|---|
date | Mon, 23 Jan 2017 22:58:36 -0700 |
parents | 0af33282b518 |
children | cad5937314cb |
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/* insn_rel.c Copyright © 2009 William Astle This file is part of LWASM. LWASM is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. */ /* for handling relative mode instructions */ #include <ctype.h> #include <stdlib.h> #include <stdio.h> #include <string.h> #include <lw_expr.h> #include "lwasm.h" #include "instab.h" /* For generic relative, the first "opcode" is the natural opcode for the mneumonic. The second "opcode" is the natural size of the relative offset. These will be used when pragma autobranchlength is NOT in effect. The third "opcode" is the short (8 bit) version of the branch. The final one is the long (16 bit) version of the branch. These will be used when pragma autobranchlength is in effect. When autobranchlength is in effect, the branch target can be prefixed with either < or > to force a short or long branch. Note that in this mode, a > or < on its own still specifies a branch point. */ PARSEFUNC(insn_parse_relgen) { lw_expr_t t = NULL, e1, e2; l -> lint = -1; l -> maxlen = OPLEN(instab[l -> insn].ops[3]) + 2; l -> minlen = OPLEN(instab[l -> insn].ops[2]) + 1; if (CURPRAGMA(l, PRAGMA_AUTOBRANCHLENGTH) == 0) { l -> lint = instab[l -> insn].ops[1]; } else { if (**p == '>' && (((*p)[1]) && !isspace((*p)[1]))) { (*p)++; l -> lint = 16; } else if (**p == '<' && (((*p)[1]) && !isspace((*p)[1]))) { (*p)++; l -> lint = 8; } } /* forced sizes handled */ // sometimes there is a "#", ignore if there if (**p == '#') (*p)++; if (CURPRAGMA(l, PRAGMA_QRTS)) { // handle ?RTS conditional return if (**p == '?') { if (strncasecmp(*p, "?RTS", 4) == 0) { (*p) += 4; line_t *cl = l; for (cl = cl->prev; cl; cl = cl->prev) { if (cl->insn == -1) continue; if (l->addr->value - cl->addr->value > 128) { cl = NULL; break; } if (cl->conditional_return) break; if (instab[cl->insn].ops[0] == 0x39) break; } if (cl) { l->lint = -1; if (cl->conditional_return) { e2 = lw_expr_build(lw_expr_type_special, lwasm_expr_lineaddr, cl); e1 = lw_expr_build(lw_expr_type_int, 2); t = lw_expr_build(lw_expr_type_oper, lw_expr_oper_plus, e1, e2); } else { t = lw_expr_build(lw_expr_type_special, lwasm_expr_lineaddr, cl); } } else { l->conditional_return = 1; // t = * + 1 e2 = lw_expr_build(lw_expr_type_special, lwasm_expr_lineaddr, l); e1 = lw_expr_build(lw_expr_type_int, 1); t = lw_expr_build(lw_expr_type_oper, lw_expr_oper_plus, e1, e2); lw_expr_destroy(e1); lw_expr_destroy(e2); } } } } if (!t) { t = lwasm_parse_expr(as, p); } if (!t) { lwasm_register_error(as, l, E_OPERAND_BAD); return; } // if we know the length of the instruction, set it now if (l -> lint == 8) { l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; if (l->conditional_return) l->len++; } else if (l -> lint == 16) { l -> len = OPLEN(instab[l -> insn].ops[3]) + 2; } // the offset calculation here depends on the length of this line! // how to calculate requirements? // this is the same problem faced by ,pcr indexing e2 = lw_expr_build(lw_expr_type_special, lwasm_expr_linelen, l); e1 = lw_expr_build(lw_expr_type_oper, lw_expr_oper_minus, t, e2); lw_expr_destroy(e2); e2 = lw_expr_build(lw_expr_type_oper, lw_expr_oper_minus, e1, l -> addr); lw_expr_destroy(e1); lwasm_save_expr(l, 0, e2); lw_expr_destroy(t); if (l -> len == -1) { e1 = lw_expr_copy(e2); l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; lwasm_reduce_expr(as, e1); l -> len = -1; if (lw_expr_istype(e1, lw_expr_type_int)) { int v; v = lw_expr_intval(e1); if (v >= -128 && v <= 127) { l -> lint = 8; l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; } else { l -> lint = 16; l -> len = OPLEN(instab[l -> insn].ops[3]) + 2; } } lw_expr_destroy(e1); } } RESOLVEFUNC(insn_resolve_relgen) { lw_expr_t e, e2; int offs; if (l -> lint == -1) { e = lwasm_fetch_expr(l, 0); if (!lw_expr_istype(e, lw_expr_type_int)) { // temporarily set the instruction length to see if we get a // constant for our expression; if so, we can select an instruction // size e2 = lw_expr_copy(e); // size of 8-bit opcode + 8 bit offset l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; lwasm_reduce_expr(as, e2); l -> len = -1; if (lw_expr_istype(e2, lw_expr_type_int)) { // it reduced to an integer; is it in 8 bit range? offs = lw_expr_intval(e2); if (offs >= -128 && offs <= 127) { // fits in 8 bits l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; l -> lint = 8; } else { // requires 16 bits l -> len = OPLEN(instab[l -> insn].ops[3]) + 2; l -> lint = 16; } } // size of 8-bit opcode + 8 bit offset l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; as -> pretendmax = 1; lwasm_reduce_expr(as, e2); as -> pretendmax = 0; l -> len = -1; if (lw_expr_istype(e2, lw_expr_type_int)) { // it reduced to an integer; is it in 8 bit range? offs = lw_expr_intval(e2); if (offs >= -128 && offs <= 127) { // fits in 8 bits with a worst case scenario l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; l -> lint = 8; } } lw_expr_destroy(e2); } if (lw_expr_istype(e, lw_expr_type_int)) { // it reduced to an integer; is it in 8 bit range? offs = lw_expr_intval(e); if (offs >= -128 && offs <= 127) { // fits in 8 bits l -> len = OPLEN(instab[l -> insn].ops[2]) + 1; l -> lint = 8; } else { // requires 16 bits l -> len = OPLEN(instab[l -> insn].ops[3]) + 2; l -> lint = 16; } } } if (!force) return; if (l -> len == -1) { l -> len = OPLEN(instab[l -> insn].ops[3]) + 2; l -> lint = 16; } } EMITFUNC(insn_emit_relgen) { lw_expr_t e; int offs; e = lwasm_fetch_expr(l, 0); if (l -> lint == 8) { if (!lw_expr_istype(e, lw_expr_type_int)) { lwasm_register_error(as, l, E_EXPRESSION_NOT_CONST); return; } offs = lw_expr_intval(e); if (l -> lint == 8 && (offs < -128 || offs > 127)) { lwasm_register_error(as, l, E_BYTE_OVERFLOW); return; } if (l->conditional_return) { lwasm_emitop(l, instab[l->insn].ops[2] ^ 1); /* flip branch, add RTS */ lwasm_emit(l, 1); lwasm_emit(l, 0x39); l->cycle_adj = 3; } else { lwasm_emitop(l, instab[l->insn].ops[2]); lwasm_emit(l, offs); } } else { lwasm_emitop(l, instab[l -> insn].ops[3]); lwasm_emitexpr(l, e, 2); } }