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x86: shrink prefix related disassembler state fields

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By changing the values used for "artificial" prefix values,
all_prefixes[] can be shrunk to array of unsigned char. All that
additionally needs adjusting is the printing of possible apparently
standalone prefixes when recovering from longjmp(): Simply check
whether any prefixes were successfully decoded, to avoid converting
opcode bytes matching the "artificial" values to prefix mnemonics.

Similarly by re-arranging the bits assigned to PREFIX_* mask values
we can fit all segment register masks in a byte and hence shrink
active_seg_prefix to unsigned char.

Somewhat similarly with last_*_prefix representing offsets into the
opcode being disassembled, signed char is sufficient to hold all possible
values.
This commit is contained in:
Jan Beulich 2022-06-13 09:52:33 +02:00
parent 384e201e5a
commit eebc56d682
1 changed files with 28 additions and 27 deletions
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55
opcodes/i386-dis.c
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@ -175,21 +175,21 @@ struct instr_info
unsigned char *insn_codep;
unsigned char *codep;
unsigned char *end_codep;
int last_lock_prefix;
int last_repz_prefix;
int last_repnz_prefix;
int last_data_prefix;
int last_addr_prefix;
int last_rex_prefix;
int last_seg_prefix;
int fwait_prefix;
signed char last_lock_prefix;
signed char last_repz_prefix;
signed char last_repnz_prefix;
signed char last_data_prefix;
signed char last_addr_prefix;
signed char last_rex_prefix;
signed char last_seg_prefix;
signed char fwait_prefix;
/* The active segment register prefix. */
int active_seg_prefix;
unsigned char active_seg_prefix;
#define MAX_CODE_LENGTH 15
/* We can up to 14 ins->prefixes since the maximum instruction length is
15bytes. */
int all_prefixes[MAX_CODE_LENGTH - 1];
unsigned char all_prefixes[MAX_CODE_LENGTH - 1];
disassemble_info *info;
struct
@ -276,13 +276,13 @@ struct instr_info
/* Flags stored in PREFIXES. */
#define PREFIX_REPZ 1
#define PREFIX_REPNZ 2
#define PREFIX_LOCK 4
#define PREFIX_CS 8
#define PREFIX_SS 0x10
#define PREFIX_DS 0x20
#define PREFIX_ES 0x40
#define PREFIX_FS 0x80
#define PREFIX_GS 0x100
#define PREFIX_CS 4
#define PREFIX_SS 8
#define PREFIX_DS 0x10
#define PREFIX_ES 0x20
#define PREFIX_FS 0x40
#define PREFIX_GS 0x80
#define PREFIX_LOCK 0x100
#define PREFIX_DATA 0x200
#define PREFIX_ADDR 0x400
#define PREFIX_FWAIT 0x800
@ -8532,13 +8532,13 @@ static const struct dis386 rm_table[][8] = {
#define INTERNAL_DISASSEMBLER_ERROR _("<internal disassembler error>")
/* We use the high bit to indicate different name for the same
prefix. */
#define REP_PREFIX (0xf3 | 0x100)
#define XACQUIRE_PREFIX (0xf2 | 0x200)
#define XRELEASE_PREFIX (0xf3 | 0x400)
#define BND_PREFIX (0xf2 | 0x400)
#define NOTRACK_PREFIX (0x3e | 0x100)
/* The values used here must be non-zero, fit in 'unsigned char', and not be
in conflict with actual prefix opcodes. */
#define REP_PREFIX 0x01
#define XACQUIRE_PREFIX 0x02
#define XRELEASE_PREFIX 0x03
#define BND_PREFIX 0x04
#define NOTRACK_PREFIX 0x05
static int
ckprefix (instr_info *ins)
@ -9519,14 +9519,15 @@ print_insn (bfd_vma pc, disassemble_info *info, int intel_syntax)
if (OPCODES_SIGSETJMP (priv.bailout) != 0)
{
const char *name;
/* Getting here means we tried for data but didn't get it. That
means we have an incomplete instruction of some sort. Just
print the first byte as a prefix or a .byte pseudo-op. */
if (ins.codep > priv.the_buffer)
{
name = prefix_name (&ins, priv.the_buffer[0], priv.orig_sizeflag);
const char *name = NULL;
if (ins.prefixes || ins.fwait_prefix >= 0 || (ins.rex & REX_OPCODE))
name = prefix_name (&ins, priv.the_buffer[0], priv.orig_sizeflag);
if (name != NULL)
i386_dis_printf (&ins, dis_style_mnemonic, "%s", name);
else