s390: Add comments to assembler operand parsing logic

gas/
	* config/tc-s390.c: Add comments to assembler operand parsing
	logic.

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

diff --git a/gas/config/tc-s390.c b/gas/config/tc-s390.c
index 55a5873edc18cecbad25590bbb0215448b00a959..9aebd8ca91e55965f608344c9c2b7955751da3b8 100644 (file)
--- a/gas/config/tc-s390.c
+++ b/gas/config/tc-s390.c
@@ -1474,9 +1474,10 @@ md_gather_operands (char *str,
          /* After a displacement a block in parentheses can start.  */
          if (*str != '(')
            {
-             /* Check if parenthesized block can be skipped. If the next
-                operand is neither an optional operand nor a base register
-                then we have a syntax error.  */
+             /* There is no opening parentheses. Check if operands of
+                parenthesized block can be skipped. Only index and base
+                register operands as well as optional operands may be
+                skipped. A length operand may not be skipped.  */
              operand = s390_operands + *(++opindex_ptr);
              if (!(operand->flags & (S390_OPERAND_INDEX|S390_OPERAND_BASE)))
                as_bad (_("syntax error; missing '(' after displacement"));
@@ -1485,6 +1486,8 @@ md_gather_operands (char *str,
              while (!(operand->flags & S390_OPERAND_BASE))
                operand = s390_operands + *(++opindex_ptr);
 
+             /* If there is no further input and the remaining operands are
+                optional then have these optional operands processed.  */
              if (*str == '\0' && skip_optargs_p (opcode->flags, &opindex_ptr[1]))
                continue;
 
@@ -1493,6 +1496,7 @@ md_gather_operands (char *str,
                {
                  if (*str != ',')
                    {
+                     /* There is no comma. Skip all operands and stop.  */
                      while (opindex_ptr[1] != '\0')
                        {
                          operand = s390_operands + *(++opindex_ptr);
@@ -1501,7 +1505,10 @@ md_gather_operands (char *str,
                        }
                    }
                  else
-                   str++;
+                   {
+                     /* Comma.  */
+                     str++;
+                   }
                }
            }
          else
@@ -1535,6 +1542,8 @@ md_gather_operands (char *str,
            str++;
          omitted_base_or_index = 0;
 
+         /* If there is no further input and the remaining operands are
+            optional then have these optional operands processed.  */
          if (*str == '\0' && skip_optargs_p (opcode->flags, &opindex_ptr[1]))
            continue;
 
@@ -1543,6 +1552,7 @@ md_gather_operands (char *str,
            {
              if (*str != ',')
                {
+                 /* There is no comma. Skip all operands and stop.  */
                  while (opindex_ptr[1] != '\0')
                    {
                      operand = s390_operands + *(++opindex_ptr);
@@ -1551,7 +1561,10 @@ md_gather_operands (char *str,
                    }
                }
              else
-               str++;
+               {
+                 /* Comma.  */
+                 str++;
+               }
            }
        }
       else
@@ -1567,6 +1580,8 @@ md_gather_operands (char *str,
              str++;
            }
 
+         /* If there is no further input and the remaining operands are
+            optional then have these optional operands processed.  */
          if (*str == '\0' && skip_optargs_p (opcode->flags, &opindex_ptr[1]))
            continue;
 
@@ -1575,6 +1590,7 @@ md_gather_operands (char *str,
            {
              if (*str != ',')
                {
+                 /* There is no comma. Skip all operands and stop.  */
                  while (opindex_ptr[1] != '\0')
                    {
                      operand = s390_operands + *(++opindex_ptr);
@@ -1583,7 +1599,10 @@ md_gather_operands (char *str,
                    }
                }
              else
-               str++;
+               {
+                 /* Comma.  */
+                 str++;
+               }
            }
        }
     }