Extend -gstrict-expr-width to cover unsized numbers.

To be strictly compliant with the standard and compatible with other
EDA tools, unsized numbers should be treated as having a fixed size
(the same size as an integer). The -gstrict-expr-width option is
extended to allow the user to enable this behaviour.

driver/iverilog.man.in

@@ -129,7 +129,9 @@ standard compliant behavior (with some loss in performance).
 .B -gstrict-expr-width\fI|\fP-gno-strict-expr-width
 Enable or disable (default) strict compliance with the standard rules
 for determining expression bit lengths. When disabled, the RHS of a
-parameter assignment is evaluated as a lossless expression.
+parameter assignment is evaluated as a lossless expression, as is any
+expression containing an unsized constant number, and unsized constant
+numbers are not truncated to integer width.
 .TP 8
 .B -I\fIincludedir\fP
 Append directory \fIincludedir\fP to list of directories searched

elab_expr.cc

@@ -4721,11 +4721,15 @@ unsigned PENumber::test_width(Design*, NetScope*, width_mode_t&mode)
 {
       expr_type_   = IVL_VT_LOGIC;
       expr_width_  = value_->len();
-      min_width_   = expr_width_;
       signed_flag_ = value_->has_sign();
 
-      if ((mode < LOSSLESS) && !value_->has_len() && !value_->is_single())
-            mode = LOSSLESS;
+      if (!value_->has_len() && !value_->is_single()) {
+	    if (gn_strict_expr_width_flag)
+		  expr_width_ = integer_width;
+	    else if (mode < LOSSLESS)
+	          mode = LOSSLESS;
+      }
+      min_width_ = expr_width_;
 
       return expr_width_;
 }

lexor.lex

@@ -801,6 +801,22 @@ void lex_end_table()
       BEGIN(INITIAL);
 }
 
+static unsigned truncate_to_integer_width(verinum::V*bits, unsigned size)
+{
+      if (size <= integer_width) return size;
+
+      verinum::V pad = bits[size-1];
+      if (pad == verinum::V1) pad = verinum::V0;
+
+      for (unsigned idx = integer_width; idx < size; idx += 1) {
+	    if (bits[idx] != pad) {
+		  yywarn(yylloc, "Unsized numeric constant truncated to integer width.");
+		  break;
+	    }
+      }
+      return integer_width;
+}
+
 verinum*make_unsized_binary(const char*txt)
 {
       bool sign_flag = false;
@@ -858,6 +874,9 @@ verinum*make_unsized_binary(const char*txt)
 	    ptr += 1;
       }
 
+      if (gn_strict_expr_width_flag && (based_size == 0))
+	    size = truncate_to_integer_width(bits, size);
+
       verinum*out = new verinum(bits, size, false);
       out->has_sign(sign_flag);
       out->is_single(single_flag);
@@ -926,6 +945,9 @@ verinum*make_unsized_octal(const char*txt)
 	    ptr += 1;
       }
 
+      if (gn_strict_expr_width_flag && (based_size == 0))
+	    size = truncate_to_integer_width(bits, size);
+
       verinum*out = new verinum(bits, size, false);
       out->has_sign(sign_flag);
       delete[]bits;
@@ -1003,6 +1025,9 @@ verinum*make_unsized_hex(const char*txt)
 	    ptr += 1;
       }
 
+      if (gn_strict_expr_width_flag && (based_size == 0))
+	    size = truncate_to_integer_width(bits, size);
+
       verinum*out = new verinum(bits, size, false);
       out->has_sign(sign_flag);
       delete[]bits;
@@ -1192,6 +1217,9 @@ verinum*make_unsized_dec(const char*ptr)
            number represents we do not check for extra bits. */
 //      if (based_size > 0) { }
 
+      if (gn_strict_expr_width_flag && (based_size == 0))
+	    size = truncate_to_integer_width(bits, size);
+
       verinum*res = new verinum(bits, size, false);
       res->has_sign(signed_flag);