x86: improve operand reversal

[binutils-gdb.git] / gas / config / tc-i386.c

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index bb1d1725d4c2f0c13c6450862a0ef9783f081ef7..b3c7334a982b686f4b423f1b094f136a80cb44d2 100644 (file)
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -376,7 +376,8 @@ struct _i386_insn
       {
        dir_encoding_default = 0,
        dir_encoding_load,
-       dir_encoding_store
+       dir_encoding_store,
+       dir_encoding_swap
       } dir_encoding;
 
     /* Prefer 8bit or 32bit displacement in encoding.  */
@@ -4516,10 +4517,11 @@ parse_insn (char *line, char *mnemonic)
 
   if (!current_templates)
     {
-      /* Check if we should swap operand or force 32bit displacement in
+      /* Deprecated functionality (new code should use pseudo-prefixes instead):
+        Check if we should swap operand or force 32bit displacement in
         encoding.  */
       if (mnem_p - 2 == dot_p && dot_p[1] == 's')
-       i.dir_encoding = dir_encoding_store;
+       i.dir_encoding = dir_encoding_swap;
       else if (mnem_p - 3 == dot_p
               && dot_p[1] == 'd'
               && dot_p[2] == '8')
@@ -5699,15 +5701,40 @@ match_template (char mnem_suffix)
            continue;
          if (!(size_match & MATCH_STRAIGHT))
            goto check_reverse;
-         /* If we want store form, we reverse direction of operands.  */
-         if (i.dir_encoding == dir_encoding_store
-             && t->opcode_modifier.d)
-           goto check_reverse;
+         /* Reverse direction of operands if swapping is possible in the first
+            place (operands need to be symmetric) and
+            - the load form is requested, and the template is a store form,
+            - the store form is requested, and the template is a load form,
+            - the non-default (swapped) form is requested.  */
+         overlap1 = operand_type_and (operand_types[0], operand_types[1]);
+         if (t->opcode_modifier.d && i.reg_operands == 2
+             && !operand_type_all_zero (&overlap1))
+           switch (i.dir_encoding)
+             {
+             case dir_encoding_load:
+               if (operand_type_check (operand_types[i.operands - 1], anymem)
+                   || operand_types[i.operands - 1].bitfield.regmem)
+                 goto check_reverse;
+               break;
+
+             case dir_encoding_store:
+               if (!operand_type_check (operand_types[i.operands - 1], anymem)
+                   && !operand_types[i.operands - 1].bitfield.regmem)
+                 goto check_reverse;
+               break;
+
+             case dir_encoding_swap:
+               goto check_reverse;
+
+             case dir_encoding_default:
+               break;
+             }
          /* Fall through.  */
 
        case 3:
          /* If we want store form, we skip the current load.  */
-         if (i.dir_encoding == dir_encoding_store
+         if ((i.dir_encoding == dir_encoding_store
+              || i.dir_encoding == dir_encoding_swap)
              && i.mem_operands == 0
              && t->opcode_modifier.load)
            continue;