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decode: Change encoding of T16 index

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This encoding change saves a shift for the "is register" part.
This commit is contained in:
Alexis Engelke
2023-03-24 13:59:38 +01:00
parent c5f5fa1f75
commit 538708cd21
2 changed files with 7 additions and 7 deletions
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8
decode.c
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@@ -179,8 +179,8 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
if (table_entry & 1) {
if (UNLIKELY(off >= len))
return FD_ERR_PARTIAL;
unsigned isreg = buffer[off] >= 0xc0 ? 8 : 0;
table_entry = table_walk(table_entry, ((buffer[off] >> 3) & 7) | isreg);
unsigned isreg = buffer[off] >= 0xc0;
table_entry = table_walk(table_entry, ((buffer[off] >> 2) & 0xe) | isreg);
// table_entry kinds: INSTR(0), T8E(1)
if (table_entry & 1)
table_entry = table_walk(table_entry, buffer[off] & 7);
@@ -314,8 +314,8 @@ fd_decode(const uint8_t* buffer, size_t len_sz, int mode_int, uintptr_t address,
if (table_entry & 1) {
if (UNLIKELY(off >= len))
return FD_ERR_PARTIAL;
unsigned isreg = buffer[off] >= 0xc0 ? 8 : 0;
table_entry = table_walk(table_entry, ((buffer[off] >> 3) & 7) | isreg);
unsigned isreg = buffer[off] >= 0xc0;
table_entry = table_walk(table_entry, ((buffer[off] >> 2) & 0xe) | isreg);
// table_entry kinds: INSTR(0), T8E(1), TVEX(2)
if (table_entry & 1)
table_entry = table_walk(table_entry, buffer[off] & 7);

6
parseinstrs.py
View File

@@ -521,14 +521,14 @@ class Trie:
elif opc.prefix:
tprefix = [["NP", "66", "F3", "F2"].index(opc.prefix)]
if opc.opcext:
t16 = [((opc.opcext - 0xc0) >> 3) | 8]
t16 = [((opc.opcext - 0xc0) >> 2) | 1]
if not opc.extended:
t8e = [opc.opcext & 7]
elif opc.modreg:
# TODO: optimize for /r and /m specifiers to reduce size
mod = {"m": [0], "r": [1<<3], "rm": [0, 1<<3]}[opc.modreg[1]]
mod = {"m": [0], "r": [1], "rm": [0, 1]}[opc.modreg[1]]
reg = [opc.modreg[0]] if opc.modreg[0] is not None else list(range(8))
t16 = [x + y for x in mod for y in reg]
t16 = [x + (y << 1) for x in mod for y in reg]
if opc.rexw is not None or (opc.vexl or "IG") != "IG":
rexw = {"0": [0], "1": [1<<0], None: [0, 1<<0]}[opc.rexw]
if opc.vex < 2: