s390: Allow to explicitly omit base register operand in assembly

The base register operand B may be omitted in D(B) by coding D and in
D(L,B) by coding D(L). The index register operand X may be omitted in
D(X,B) by coding D(B) or explicitly omitted by coding D(,B). In both
cases the omitted base register operand value defaults to zero.

Allow to explicitly omit the base register operand B in D(X,B) and
D(L,B) by coding D(X,) and D(L,). Default the omitted base register
operand value to zero.

gas/
	* config/tc-s390.c: Allow to explicitly omit the base register
	operand in assembly.
	* NEWS: Mention that the base register now may be omitted on
	s390.
	* gas/testsuite/gas/s390/zarch-base-index-0.s: Update test cases
	for change to allow to explicitly omit the base register
	operand in assembly.
	* gas/testsuite/gas/s390/zarch-base-index-0.d: Likewise.
	* gas/testsuite/gas/s390/zarch-base-index-0-err.s: Likewise.
	* gas/testsuite/gas/s390/zarch-base-index-0-err.l: Likewise.
	* gas/testsuite/gas/s390/zarch-omitted-base-index.s: Likewise.
	* gas/testsuite/gas/s390/zarch-omitted-base-index.d: Likewise.
	* gas/testsuite/gas/s390/zarch-omitted-base-index-err.s:
	Likewise.
	* gas/testsuite/gas/s390/zarch-omitted-base-index-err.l:
	Likewise.

Reviewed-by: Andreas Krebbel <krebbel@linux.ibm.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/gas/config/tc-s390.c b/gas/config/tc-s390.c
index 9659875..edf8883 100644
--- a/gas/config/tc-s390.c
+++ b/gas/config/tc-s390.c
@@ -1683,13 +1683,17 @@ md_gather_operands (char *str,
       else
 	{
 	  /* We can find an 'early' closing parentheses in e.g. D(L) instead
-	     of D(L,B).  In this case the base register has to be skipped.  */
-	  if (*str == ')')
+	     of D(L,B). In this case the base register has to be skipped.
+	     Same if the base register has been explicilty omitted in e.g.
+	     D(X,) or D(L,).  */
+	  if (*str == ')' || (str[0] == ',' && str[1] == ')'))
 	    {
 	      operand = s390_operands + *(++opindex_ptr);
 
 	      if (!(operand->flags & S390_OPERAND_BASE))
-		as_bad (_("syntax error; ')' not allowed here"));
+		as_bad (_("syntax error; '%c' not allowed here"), *str);
+	      if (*str == ',')
+		str++;
 	      str++;
 	    }