[PATCH] x86: change type of Dwarf2 register numbers in register table

[Jan Beulich <jbeulich@suse.com>]

Already the %bnd<N> registers used numbers beyond 127, and eGPR ones are
all out of reach for "signed char", at least when CHAR_BITS=8. Switch to
"unsigned char", covering appropriately in places where the value
returned for "none" actually matters (in tc_x86_parse_to_dw2regnum()
this is actually achieved by altering how X_op is set).
---
I question the use of flag_code here, btw: Imo the choice ought to be
tied to object format, not present assembly mode. Thoughts?

--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -5395,10 +5395,8 @@ ginsn_opsize_prefix_p (void)
 static unsigned int
 ginsn_dw2_regnum (const reg_entry *ireg)
 {
-  /* PS: Note the data type here as int32_t, because of Dw2Inval (-1).  */
-  int32_t dwarf_reg = Dw2Inval;
   const reg_entry *temp = ireg;
-  unsigned int idx = 0;
+  unsigned int dwarf_reg = Dw2Inval, idx = 0;
 
   /* ginsn creation is available for AMD64 abi only ATM.  Other flag_code
      are not expected.  */
@@ -5441,7 +5439,7 @@ ginsn_dw2_regnum (const reg_entry *ireg)
 
   /* Sanity check - failure may indicate state corruption, bad ginsn or
      perhaps the i386-reg table and the current function got out of sync.  */
-  gas_assert (dwarf_reg >= 0);
+  gas_assert (dwarf_reg < Dw2Inval);
 
   return (unsigned int) dwarf_reg;
 }
@@ -17459,14 +17457,14 @@ tc_x86_parse_to_dw2regnum (expressionS *
 
   if (exp->X_op == O_register && exp->X_add_number >= 0)
     {
+      exp->X_op = O_illegal;
       if ((addressT) exp->X_add_number < i386_regtab_size)
 	{
-	  exp->X_op = O_constant;
 	  exp->X_add_number = i386_regtab[exp->X_add_number]
 			      .dw2_regnum[flag_code >> 1];
+	  if (exp->X_add_number != Dw2Inval)
+	    exp->X_op = O_constant;
 	}
-      else
-	exp->X_op = O_illegal;
     }
 }
 
--- a/opcodes/i386-opc.h
+++ b/opcodes/i386-opc.h
@@ -1051,7 +1051,7 @@ typedef struct
 #define RegIZ	(RegIP - 1)
 /* FLAT is a fake segment register (Intel mode).  */
 #define RegFlat     ((unsigned char) ~0)
-  signed char dw2_regnum[2];
-#define Dw2Inval (-1)
+  unsigned char dw2_regnum[2];
+#define Dw2Inval 0xff
 }
 reg_entry;