[PATCH] x86: rework UWRMSR operand swapping

[Jan Beulich]

As indicated during review already, doing the swapping early is overall
cheaper than doing it only after operand matching.

--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -5201,10 +5201,14 @@ md_assemble (char *line)
 	   && operand_type_check (i.types[1], imm)))
     swap_operands ();
 
-  /* The order of the immediates should be reversed
-     for 2 immediates extrq and insertq instructions */
-  if (i.imm_operands == 2
-      && (t->mnem_off == MN_extrq || t->mnem_off == MN_insertq))
+  /* The order of the immediates should be reversed for 2-immediates extrq
+     and insertq instructions.  Also UWRMSR wants its immediate to be in the
+     "canonical" place (first), despite it appearing last (in AT&T syntax, or
+     because of the swapping above) in the incoming set of operands.  */
+  if ((i.imm_operands == 2
+       && (t->mnem_off == MN_extrq || t->mnem_off == MN_insertq))
+      || (t->mnem_off == MN_uwrmsr && i.imm_operands
+	  && i.operands > i.imm_operands))
       swap_2_operands (0, 1);
 
   if (i.imm_operands)
@@ -7557,17 +7561,6 @@ match_template (char mnem_suffix)
       break;
     }
 
-  /* This pattern aims to put the unusually placed imm operand to a usual
-     place. The constraints are currently only adapted to uwrmsr, and may
-     need further tweaking when new similar instructions become available.  */
-  if (i.imm_operands && i.imm_operands < i.operands
-      && operand_type_check (operand_types[i.operands - 1], imm))
-    {
-      i.tm.operand_types[0] = operand_types[i.operands - 1];
-      i.tm.operand_types[i.operands - 1] = operand_types[0];
-      swap_2_operands(0, i.operands - 1);
-    }
-
   return t;
 }
 
--- a/opcodes/i386-opc.tbl
+++ b/opcodes/i386-opc.tbl
@@ -3354,6 +3354,8 @@ eretu, 0xf30f01ca, FRED&x64, NoSuf, {}
 urdmsr, 0xf20f38f8, USER_MSR|x64, RegMem|NoSuf|NoRex64, { Reg64, Reg64 }
 urdmsr, 0xf2f8/0, USER_MSR|x64, Modrm|Vex128|VexMap7|VexW0|NoSuf, { Imm32, Reg64 }
 uwrmsr, 0xf30f38f8, USER_MSR|x64, Modrm|NoSuf|NoRex64, { Reg64, Reg64 }
-uwrmsr, 0xf3f8/0, USER_MSR|x64, Modrm|Vex128|VexMap7|VexW0|NoSuf, { Reg64, Imm32 }
+// Immediates want to be first; md_assemble() takes care of swapping operands
+// accordingly.
+uwrmsr, 0xf3f8/0, USER_MSR|x64, Modrm|Vex128|VexMap7|VexW0|NoSuf, { Imm32, Reg64 }
 
 // USER_MSR instructions end.