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decode: Encode prefixes in trie

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This allows to handle unescaped opcodes with a single table lookup.
This commit is contained in:
Alexis Engelke
2023-03-22 09:57:58 +01:00
parent a34cd9d2aa
commit e1084be859
2 changed files with 107 additions and 41 deletions
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51
parseinstrs.py
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@@ -324,6 +324,8 @@ class InstrDesc(NamedTuple):
class EntryKind(Enum):
NONE = 0
PREFIX = 8
ESCAPE = 7
INSTR = 1
WEAKINSTR = 9
TABLE256 = 2
@@ -334,7 +336,7 @@ class EntryKind(Enum):
TABLE_ROOT = -1
@property
def is_table(self):
return self != EntryKind.INSTR and self != EntryKind.WEAKINSTR
return self != EntryKind.INSTR and self != EntryKind.WEAKINSTR and self != EntryKind.PREFIX
opcode_regex = re.compile(
r"^(?:(?P<prefixes>(?P<vex>E?VEX\.)?(?P<legacy>NP|66|F2|F3|NFx)\." +
@@ -392,6 +394,8 @@ def verifyOpcodeDesc(opcode, desc):
raise Exception(f"unescaped opcode has L specifier {opcode}, {desc}")
if opcode.escape == 0 and opcode.rexw is not None:
raise Exception(f"unescaped opcode has W specifier {opcode}, {desc}")
if opcode.escape == 0 and opcode.vex:
raise Exception(f"VEX opcode without escape {opcode}, {desc}")
if opcode.vex and opcode.prefix not in ("NP", "66", "F2", "F3"):
raise Exception(f"VEX/EVEX must have mandatory prefix {opcode}, {desc}")
if opcode.vexl == "IG" and desc.dynsizes() - {OpKind.SZ_OP}:
@@ -456,11 +460,12 @@ def verifyOpcodeDesc(opcode, desc):
raise Exception(f"memory size {opsz} != {tupsz} {opcode}, {desc}")
class Trie:
KIND_ORDER = (EntryKind.TABLE_ROOT, EntryKind.TABLE256,
KIND_ORDER = (EntryKind.TABLE_ROOT, EntryKind.ESCAPE, EntryKind.TABLE256,
EntryKind.TABLE_PREFIX, EntryKind.TABLE16,
EntryKind.TABLE8E, EntryKind.TABLE_VEX)
TABLE_LENGTH = {
EntryKind.TABLE_ROOT: 16,
EntryKind.TABLE_ROOT: 256,
EntryKind.ESCAPE: 8,
EntryKind.TABLE256: 256,
EntryKind.TABLE_PREFIX: 4,
EntryKind.TABLE16: 16,
@@ -486,8 +491,22 @@ class Trie:
return elem[0], new_num
def _transform_opcode(self, opc):
troot = [opc.escape | opc.vex << 2]
t256 = [opc.opc + i for i in range(8 if opc.extended and not opc.opcext else 1)]
topc = [opc.opc + i for i in range(8 if opc.extended and not opc.opcext else 1)]
if opc.escape == 0 and opc.opc in (0xc4, 0xc5, 0x62):
assert opc.prefix is None
assert opc.opcext is None
assert opc.modreg == (None, "m")
assert opc.rexw is None
assert opc.vexl is None
# We do NOT encode /m, this is handled by prefix code.
# Order must match KIND_ORDER.
return topc, [0], None, None, None, None, None
elif opc.escape == 0:
troot, tescape, topc = topc, None, None
else:
troot = [[0x0f], [0xc4, 0xc5], [0x62]][opc.vex]
tescape = [opc.escape]
tprefix, t16, t8e, tvex = None, None, None, None
if opc.prefix == "NFx":
tprefix = [0, 1]
@@ -510,7 +529,7 @@ class Trie:
vexl = {"0": [0], "12": [1<<1, 2<<1], "2": [2<<1], "IG": [0, 1<<1, 2<<1, 3<<1]}[opc.vexl or "IG"]
tvex = list(map(sum, product(rexw, vexl)))
# Order must match KIND_ORDER.
return troot, t256, tprefix, t16, t8e, tvex
return troot, tescape, topc, tprefix, t16, t8e, tvex
def add_opcode(self, opcode, descidx, root_idx, weak=False):
opcode = self._transform_opcode(opcode)
@@ -546,6 +565,11 @@ class Trie:
elif not weak:
raise Exception(f"redundant non-weak {opcode}")
def add_prefix(self, byte, prefix, root_idx):
if self.trie[0][root_idx] is None:
self.trie[0][root_idx] = EntryKind.TABLE_ROOT, self._add_table(EntryKind.TABLE_ROOT)
self.trie[self.trie[0][root_idx][1]][byte] = EntryKind.PREFIX, prefix
def deduplicate(self):
synonyms = {}
for kind in self.KIND_ORDER[::-1]:
@@ -627,6 +651,21 @@ def decode_table(entries, args):
modes = args.modes
trie = Trie(root_count=len(modes))
for i, mode in enumerate(modes):
# Magic values must match PF_* enum in decode.c.
trie.add_prefix(0x66, 0xfffa, i)
trie.add_prefix(0x67, 0xfffb, i)
trie.add_prefix(0xf0, 0xfffc, i)
trie.add_prefix(0xf2, 0xfffd, i)
trie.add_prefix(0xf3, 0xfffd, i)
trie.add_prefix(0x64, 0xfff9, i)
trie.add_prefix(0x65, 0xfff9, i)
for seg in (0x26, 0x2e, 0x36, 0x3e):
trie.add_prefix(seg, 0xfff8 + (mode <= 32), i)
if mode > 32:
for rex in range(0x40, 0x50):
trie.add_prefix(rex, 0xfffe, i)
mnems, descs, desc_map = set(), [], {}
for weak, opcode, desc in entries:
ign66 = opcode.prefix in ("NP", "66", "F2", "F3")