iverilog/tgt-vlog95/expr.c

/*
 * Copyright (C) 2011 Cary R. (cygcary@yahoo.com)
 *
 *  This program 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 2 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, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *
 * This is the vlog95 target module. It generates a 1364-1995 compliant
 * netlist from the input netlist. The generated netlist is expected to
 * be simulation equivalent to the original.
 */

# include "config.h"
# include "vlog95_priv.h"

// HERE: Do we need to use scope and wid?

static void emit_expr_binary(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      char *oper = "<invalid>";
      switch(ivl_expr_opcode(expr)) {
	case '+': oper = "+"; break;
	case '-': oper = "-"; break;
	case '*': oper = "*"; break;
	case '/': oper = "/"; break;
	case '%': oper = "%"; break;
	case 'p': oper = "**"; break;
	case 'E': oper = "==="; break;
	case 'e': oper = "=="; break;
	case 'N': oper = "!=="; break;
	case 'n': oper = "!="; break;
	case '<': oper = "<"; break;
	case 'L': oper = "<="; break;
	case '>': oper = ">"; break;
	case 'G': oper = ">="; break;
	case '&': oper = "&"; break;
	case '|': oper = "|"; break;
	case '^': oper = "^"; break;
	case 'A': oper = "&"; break;
	case 'O': oper = "|"; break;
	case 'X': oper = "~^"; break;
	case 'a': oper = "&&"; break;
	case 'o': oper = "||"; break;
	case 'l': oper = "<<"; break;
	case 'r': oper = ">>"; break;
	case 'R': oper = ">>>"; break;
      }

      fprintf(vlog_out, "(");
      switch(ivl_expr_opcode(expr)) {
	case '+':
	case '-':
	case '*':
	case '/':
	case '%':
	case 'E':
	case 'e':
	case 'N':
	case 'n':
	case '<':
	case 'L':
	case '>':
	case 'G':
	case '&':
	case '|':
	case '^':
	case 'X':
// HERE: Do these two need to be done differently (wid = 0)?
	case 'a':
	case 'o':
// HERE: Do these two need to be done differently (r-value wid = 0)?
	case 'l':
	case 'r':
	case 'R':
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    fprintf(vlog_out, " %s ", oper);
	    emit_expr(scope, ivl_expr_oper2(expr), wid);
	    break;
	case 'A':
	case 'O':
	    fprintf(vlog_out, "~(");
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    fprintf(vlog_out, " %s ", oper);
	    emit_expr(scope, ivl_expr_oper2(expr), wid);
	    fprintf(vlog_out, ")");
	    break;
	case 'p':
// HERE: We can convert 2 ** <r-val> to 1 << <r-val>
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    fprintf(vlog_out, " ** ");
	    emit_expr(scope, ivl_expr_oper2(expr), 0);
	    fprintf(stderr, "%s:%u: vlog95 error: Power operator is not "
	                    "supported.\n",
	                    ivl_expr_file(expr), ivl_expr_lineno(expr));
	    vlog_errors += 1;
	    break;
	default:
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    fprintf(vlog_out, "<unknown>");
	    emit_expr(scope, ivl_expr_oper2(expr), wid);
	    fprintf(stderr, "%s:%u: vlog95 error: Unknown expression "
	                    "operator (%c).\n",
	                    ivl_expr_file(expr),
	                    ivl_expr_lineno(expr),
	                    ivl_expr_opcode(expr));
	    vlog_errors += 1;
	    break;
      }
      fprintf(vlog_out, ")");
}

static void emit_expr_number(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      const char *bits = ivl_expr_bits(expr);
      unsigned nbits = ivl_expr_width(expr);
	/* A signed value can only be 32 bits long since it can only be
	 * represented as an integer. We can trim any matching MSB bits
	 * to make it fit. We do not support undefined bits. */
      if (ivl_expr_signed(expr)) {
	    unsigned trim_wid = nbits - 1;
	    const char msb = bits[trim_wid];
	    for (/* none */; trim_wid > 0; trim_wid -= 1) {
		  if (msb != bits[trim_wid]) {
			trim_wid += 1;
			break;
		  }
	    }
	    trim_wid += 1;
	    if (trim_wid > 32U) {
		  fprintf(vlog_out, "<oversized_signed>");
		  fprintf(stderr, "%s:%u: vlog95 error: Signed number is "
		          "greater than 32 bits (%u) and cannot be safely "
		          "represented.\n",
		          ivl_expr_file(expr), ivl_expr_lineno(expr), trim_wid);
		  vlog_errors += 1;
		  return;
	    } else {
		  unsigned idx;
		  int32_t value = 0;
		  for (idx = 0; idx < trim_wid; idx += 1) {
			if (bits[idx] == '1') value |= 1U << idx;
			else if (bits[idx] != '0') {
			      fprintf(vlog_out, "<undefined_signed>");
			      fprintf(stderr, "%s:%u: vlog95 error: Signed "
			                      "number has an undefined bit "
			                      "and cannot be represented.\n",
			                      ivl_expr_file(expr),
			                      ivl_expr_lineno(expr));
			      vlog_errors += 1;
			      return;
			}
		  }
		    /* Sign extend as needed. */
		  if (msb == '1' && trim_wid < 32U) {
			value |= ~((1U << trim_wid) - 1U);
		  }
		  fprintf(vlog_out, "%"PRId32, value);
	    }
	/* An unsigned number is always represented in binary form to
	 * preserve all the information. */
      } else {
	    int idx;
	    fprintf(vlog_out, "%u'b", nbits);
	    for (idx = (int)nbits-1; idx >= 0; idx -= 1) {
		  fprintf(vlog_out, "%c", bits[idx]);
	    }
      }
}

static void emit_expr_select(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      if (ivl_expr_oper2(expr)) {
      } else {
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
      }
}

static void emit_expr_signal(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      ivl_signal_t sig = ivl_expr_signal(expr);
// HERE: Need support for an array select and an out of scope reference.
//       Also pad a signed value to the given width.
      fprintf(vlog_out, "%s", ivl_signal_basename(sig));
}

static void emit_expr_unary(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      char *oper = "invalid";
      switch (ivl_expr_opcode(expr)) {
	case '-': oper = "-"; break;
	case '~': oper = "~"; break;
	case '&': oper = "&"; break;
	case '|': oper = "|"; break;
	case '^': oper = "^"; break;
	case 'A': oper = "~&"; break;
	case 'N': oper = "~|"; break;
	case 'X': oper = "~^"; break;
	case '!': oper = "!"; break;
      }
      switch (ivl_expr_opcode(expr)) {
	case '-':
	case '~':
	case '&':
	case '|':
	case '^':
	case 'A':
	case 'N':
	case 'X':
	    fprintf(vlog_out, "%s", oper);
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    break;
	case '2':
	case 'i':
	case 'r':
	    /* A cast is a noop. */
	    break;
	default:
	    fprintf(vlog_out, "<unknown>");
	    emit_expr(scope, ivl_expr_oper1(expr), wid);
	    fprintf(stderr, "%s:%u: vlog95 error: Unknown unary "
	                    "operator (%c).\n",
	                    ivl_expr_file(expr),
	                    ivl_expr_lineno(expr),
	                    ivl_expr_opcode(expr));
	    break;
      }
}

void emit_expr(ivl_scope_t scope, ivl_expr_t expr, unsigned wid)
{
      switch(ivl_expr_type(expr)) {
	case IVL_EX_BINARY:
	    emit_expr_binary(scope, expr, wid);
	    break;
	case IVL_EX_NUMBER:
	    emit_expr_number(scope, expr, wid);
	    break;
	case IVL_EX_REALNUM:
	    fprintf(vlog_out, "%#g", ivl_expr_dvalue(expr));
	    break;
	case IVL_EX_SELECT:
	    emit_expr_select(scope, expr, wid);
	    break;
	case IVL_EX_SIGNAL:
	    emit_expr_signal(scope, expr, wid);
	    break;
	case IVL_EX_STRING:
	    fprintf(vlog_out, "\"%s\"", ivl_expr_string(expr));
	    break;
	case IVL_EX_UNARY:
	    emit_expr_unary(scope, expr, wid);
	    break;
	default:
	    fprintf(vlog_out, "<unknown>");
	    fprintf(stderr, "%s:%u: vlog95 error: Unknown expression "
	                    "type (%d).\n",
	                    ivl_expr_file(expr),
	                    ivl_expr_lineno(expr),
	                    (int)ivl_expr_type(expr));
	    vlog_errors += 1;
	    break;
      }
}