Support AMD64/Intel ISAs in assembler/disassembler

AMD64 spec and Intel64 spec differ in direct unconditional branches in
64-bit mode.  AMD64 supports direct unconditional branches with 16-bit
offset via the data size prefix, which truncates RIP to 16 bits, while
the data size prefix is ignored by Intel64.

This patch adds -mamd64/-mintel64 option to x86-64 assembler and
-Mamd64/-Mintel64 option to x86-64 disassembler.  The most permissive
ISA, which is AMD64, is the default.

GDB can add an option, similar to

(gdb) help set disassembly-flavor
Set the disassembly flavor.
The valid values are "att" and "intel", and the default value is "att".

to select which ISA to disassemble.

binutils/

	PR binutis/18386
	* doc/binutils.texi: Document -Mamd64 and -Mintel64.

gas/

	PR binutis/18386
	* config/tc-i386.c (OPTION_MAMD64): New.
	(OPTION_MINTEL64): Likewise.
	(md_longopts): Add -mamd64 and -mintel64.
	(md_parse_option): Handle OPTION_MAMD64 and OPTION_MINTEL64.
	(md_show_usage): Add -mamd64 and -mintel64.
	* doc/c-i386.texi: Document -mamd64 and -mintel64.

gas/testsuite/

	PR binutis/18386
	* gas/i386/i386.exp: Run x86-64-branch-2 and x86-64-branch-3.
	* gas/i386/x86-64-branch.d: Also pass -Mintel64 to objdump.
	* gas/i386/ilp32/x86-64-branch.d: Likewise.
	* gas/i386/x86-64-branch-2.d: New file.
	* gas/i386/x86-64-branch-2.s: Likewise.
	* gas/i386/x86-64-branch-3.l: Likewise.
	* gas/i386/x86-64-branch-3.s: Likewise.

ld/testsuite/

	PR binutis/18386
	* ld-x86-64/tlsgdesc.dd: Also pass -Mintel64 to objdump.
	* ld-x86-64/tlspic.dd: Likewise.
	* ld-x86-64/x86-64.exp (x86_64tests): Also pass -Mintel64 to
	objdump for tlspic.dd and tlsgdesc.dd.

opcodes/

	PR binutis/18386
	* i386-dis.c: Add comments for '@'.
	(x86_64_table): Use '@' on call/jmp for X86_64_E8/X86_64_E9.
	(enum x86_64_isa): New.
	(isa64): Likewise.
	(print_i386_disassembler_options): Add amd64 and intel64.
	(print_insn): Handle amd64 and intel64.
	(putop): Handle '@'.
	(OP_J): Don't ignore the operand size prefix for AMD64 in 64-bit.
	* i386-gen.c (cpu_flags): Add CpuAMD64 and CpuIntel64.
	* i386-opc.h (AMD64): New.
	(CpuIntel64): Likewise.
	(i386_cpu_flags): Add cpuamd64 and cpuintel64.
	* i386-opc.tbl: Add direct call/jmp with Disp16|Disp32 for AMD64.
	Mark direct call/jmp without Disp16|Disp32 as Intel64.
	* i386-init.h: Regenerated.
	* i386-tbl.h: Likewise.

gas/config/tc-i386.c

@@ -9550,6 +9550,8 @@ const char *md_shortopts = "qn";
 #define OPTION_OMIT_LOCK_PREFIX (OPTION_MD_BASE + 19)
 #define OPTION_MEVEXRCIG (OPTION_MD_BASE + 20)
 #define OPTION_MSHARED (OPTION_MD_BASE + 21)
+#define OPTION_MAMD64 (OPTION_MD_BASE + 22)
+#define OPTION_MINTEL64 (OPTION_MD_BASE + 23)
 
 struct option md_longopts[] =
 {
@@ -9582,6 +9584,8 @@ struct option md_longopts[] =
 #endif
   {"momit-lock-prefix", required_argument, NULL, OPTION_OMIT_LOCK_PREFIX},
   {"mevexrcig", required_argument, NULL, OPTION_MEVEXRCIG},
+  {"mamd64", no_argument, NULL, OPTION_MAMD64},
+  {"mintel64", no_argument, NULL, OPTION_MINTEL64},
   {NULL, no_argument, NULL, 0}
 };
 size_t md_longopts_size = sizeof (md_longopts);
@@ -9898,6 +9902,20 @@ md_parse_option (int c, char *arg)
         as_fatal (_("invalid -momit-lock-prefix= option: `%s'"), arg);
       break;
 
+    case OPTION_MAMD64:
+      cpu_arch_flags.bitfield.cpuamd64 = 1;
+      cpu_arch_flags.bitfield.cpuintel64 = 0;
+      cpu_arch_isa_flags.bitfield.cpuamd64 = 1;
+      cpu_arch_isa_flags.bitfield.cpuintel64 = 0;
+      break;
+
+    case OPTION_MINTEL64:
+      cpu_arch_flags.bitfield.cpuamd64 = 0;
+      cpu_arch_flags.bitfield.cpuintel64 = 1;
+      cpu_arch_isa_flags.bitfield.cpuamd64 = 0;
+      cpu_arch_isa_flags.bitfield.cpuintel64 = 1;
+      break;
+
     default:
       return 0;
     }
@@ -10063,6 +10081,10 @@ md_show_usage (FILE *stream)
   fprintf (stream, _("\
   -momit-lock-prefix=[no|yes]\n\
                           strip all lock prefixes\n"));
+  fprintf (stream, _("\
+  -mamd64                 accept only AMD64 ISA\n"));
+  fprintf (stream, _("\
+  -mintel64               accept only Intel64 ISA\n"));
 }
 
 #if ((defined (OBJ_MAYBE_COFF) && defined (OBJ_MAYBE_AOUT)) \