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encode: Remove descriptor table

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All relevant information is now encoded directly in the numeric value of
the mnemonic, significantly shrinking the size of the encoder.
This commit is contained in:
Alexis Engelke
2023-01-13 14:23:07 +01:00
parent 9f0ddeb44a
commit 2f7e8dd0de
4 changed files with 174 additions and 184 deletions
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270
encode.c
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@@ -14,39 +14,38 @@
#define UNLIKELY(x) (x)
#endif
enum {
// 16:17 = escape
OPC_0F = 1 << 16,
OPC_0F38 = 2 << 16,
OPC_0F3A = 3 << 16,
OPC_ESCAPE_MSK = 3 << 16,
OPC_VSIB = 1 << 18,
OPC_66 = 1 << 19,
OPC_F2 = 1 << 20,
OPC_F3 = 1 << 21,
OPC_REXW = 1 << 22,
OPC_LOCK = 1 << 23,
OPC_VEX = 1 << 24,
OPC_VEXL = 1 << 25,
OPC_REXR = 1 << 28,
OPC_REXX = 1 << 27,
OPC_REXB = 1 << 26,
OPC_REX = 1 << 29,
OPC_67 = 1 << 30,
};
#define OPC_66 0x80000
#define OPC_F2 0x100000
#define OPC_F3 0x200000
#define OPC_REXW 0x400000
#define OPC_LOCK 0x800000
#define OPC_VEXL0 0x1000000
#define OPC_VEXL1 0x1800000
#define OPC_EVEXL0 0x2000000
#define OPC_EVEXL1 0x2800000
#define OPC_EVEXL2 0x3000000
#define OPC_EVEXL3 0x3800000
#define OPC_EVEXB 0x4000000
#define OPC_VSIB 0x8000000
#define OPC_67 FE_ADDR32
#define OPC_SEG_MSK 0xe0000000
#define OPC_JMPL FE_JMPL
#define OPC_MASK_MSK 0x1e00000000
#define OPC_USER_MSK (OPC_67|OPC_SEG_MSK|OPC_MASK_MSK)
#define OPC_GPH_OP0 0x200000000000
#define OPC_GPH_OP1 0x400000000000
#define OPC_SEG_IDX 31
#define OPC_SEG_MSK ((uint64_t) 0x7l << OPC_SEG_IDX)
#define OPC_VEXOP_IDX 34
#define OPC_VEXOP_MSK ((uint64_t) 0xfl << OPC_VEXOP_IDX)
#define EPFX_REX_MSK 0x0f
#define EPFX_REX 0x08
#define EPFX_REXR 0x04
#define EPFX_REXX 0x02
#define EPFX_REXB 0x01
#define EPFX_VVVV_IDX 4
static bool op_mem(FeOp op) { return op < 0; }
static bool op_reg(FeOp op) { return op >= 0; }
static bool op_reg_gpl(FeOp op) { return (op & ~0xf) == 0x100; }
static bool op_reg_gph(FeOp op) { return (op & ~0x3) == 0x204; }
static bool op_reg_seg(FeOp op) { return (op & ~0x7) == 0x300 && (op & 7) < 6; }
static bool op_reg_fpu(FeOp op) { return (op & ~0x7) == 0x400; }
static bool op_reg_mmx(FeOp op) { return (op & ~0x7) == 0x500; }
static bool op_reg_xmm(FeOp op) { return (op & ~0xf) == 0x600; }
static int64_t op_mem_offset(FeOp op) { return (int32_t) op; }
static unsigned op_mem_base(FeOp op) { return (op >> 32) & 0xfff; }
@@ -65,11 +64,13 @@ static bool op_imm_n(FeOp imm, unsigned immsz) {
static
unsigned
opc_size(uint64_t opc)
opc_size(uint64_t opc, uint64_t epfx)
{
unsigned res = 1;
if (opc & OPC_VEX) {
if ((opc & (OPC_REXW|OPC_REXX|OPC_REXB|OPC_ESCAPE_MSK)) != OPC_0F)
if (opc & OPC_EVEXL0) {
res += 4;
} else if (opc & OPC_VEXL0) {
if (opc & (OPC_REXW|0x20000) || epfx & (EPFX_REXX|EPFX_REXB))
res += 3;
else
res += 2;
@@ -78,63 +79,64 @@ opc_size(uint64_t opc)
if (opc & OPC_66) res++;
if (opc & OPC_F2) res++;
if (opc & OPC_F3) res++;
if (opc & (OPC_REX|OPC_REXW|OPC_REXR|OPC_REXX|OPC_REXB)) res++;
if (opc & OPC_ESCAPE_MSK) res++;
if ((opc & OPC_ESCAPE_MSK) == OPC_0F38 || (opc & OPC_ESCAPE_MSK) == OPC_0F3A) res++;
if (opc & OPC_REXW || epfx & EPFX_REX_MSK) res++;
if (opc & 0x30000) res++;
if (opc & 0x20000) res++;
}
if (opc & OPC_SEG_MSK) res++;
if (opc & OPC_67) res++;
if ((opc & 0xc000) == 0xc000) res++;
if (opc & 0x8000) res++;
return res;
}
static
int
enc_opc(uint8_t** restrict buf, uint64_t opc)
enc_opc(uint8_t** restrict buf, uint64_t opc, uint64_t epfx)
{
if (opc & OPC_SEG_MSK)
*(*buf)++ = (0x65643e362e2600 >> (8 * ((opc >> OPC_SEG_IDX) & 7))) & 0xff;
*(*buf)++ = (0x65643e362e2600 >> (8 * ((opc >> 29) & 7))) & 0xff;
if (opc & OPC_67) *(*buf)++ = 0x67;
if (opc & OPC_VEX) {
bool vex3 = (opc & (OPC_REXW|OPC_REXX|OPC_REXB|OPC_ESCAPE_MSK)) != OPC_0F;
if (opc & OPC_EVEXL0) {
return -1;
} else if (opc & OPC_VEXL0) {
bool vex3 = opc & (OPC_REXW|0x20000) || epfx & (EPFX_REXX|EPFX_REXB);
unsigned pp = 0;
if (opc & OPC_66) pp = 1;
if (opc & OPC_F3) pp = 2;
if (opc & OPC_F2) pp = 3;
*(*buf)++ = 0xc4 | !vex3;
unsigned b2 = pp | (opc & OPC_VEXL ? 0x4 : 0);
unsigned b2 = pp | (opc & 0x800000 ? 0x4 : 0);
if (vex3) {
unsigned b1 = (opc & OPC_ESCAPE_MSK) >> 16;
if (!(opc & OPC_REXR)) b1 |= 0x80;
if (!(opc & OPC_REXX)) b1 |= 0x40;
if (!(opc & OPC_REXB)) b1 |= 0x20;
unsigned b1 = opc >> 16 & 3;
if (!(epfx & EPFX_REXR)) b1 |= 0x80;
if (!(epfx & EPFX_REXX)) b1 |= 0x40;
if (!(epfx & EPFX_REXB)) b1 |= 0x20;
*(*buf)++ = b1;
if (opc & OPC_REXW) b2 |= 0x80;
} else {
if (!(opc & OPC_REXR)) b2 |= 0x80;
if (!(epfx & EPFX_REXR)) b2 |= 0x80;
}
b2 |= (~((opc & OPC_VEXOP_MSK) >> OPC_VEXOP_IDX) & 0xf) << 3;
b2 |= (~(epfx >> EPFX_VVVV_IDX) & 0xf) << 3;
*(*buf)++ = b2;
} else {
if (opc & OPC_LOCK) *(*buf)++ = 0xF0;
if (opc & OPC_66) *(*buf)++ = 0x66;
if (opc & OPC_F2) *(*buf)++ = 0xF2;
if (opc & OPC_F3) *(*buf)++ = 0xF3;
if (opc & (OPC_REX|OPC_REXW|OPC_REXR|OPC_REXX|OPC_REXB))
{
if (opc & OPC_REXW || epfx & (EPFX_REX_MSK)) {
unsigned rex = 0x40;
if (opc & OPC_REXW) rex |= 8;
if (opc & OPC_REXR) rex |= 4;
if (opc & OPC_REXX) rex |= 2;
if (opc & OPC_REXB) rex |= 1;
if (epfx & EPFX_REXR) rex |= 4;
if (epfx & EPFX_REXX) rex |= 2;
if (epfx & EPFX_REXB) rex |= 1;
*(*buf)++ = rex;
}
if (opc & OPC_ESCAPE_MSK) *(*buf)++ = 0x0F;
if ((opc & OPC_ESCAPE_MSK) == OPC_0F38) *(*buf)++ = 0x38;
if ((opc & OPC_ESCAPE_MSK) == OPC_0F3A) *(*buf)++ = 0x3A;
if (opc & 0x30000) *(*buf)++ = 0x0F;
if ((opc & 0x30000) == 0x20000) *(*buf)++ = 0x38;
if ((opc & 0x30000) == 0x30000) *(*buf)++ = 0x3A;
}
*(*buf)++ = opc & 0xff;
if ((opc & 0xc000) == 0xc000) *(*buf)++ = (opc >> 8) & 0xff;
if (opc & 0x8000) *(*buf)++ = (opc >> 8) & 0xff;
return 0;
}
@@ -150,32 +152,32 @@ enc_imm(uint8_t** restrict buf, uint64_t imm, unsigned immsz)
static
int
enc_o(uint8_t** restrict buf, uint64_t opc, uint64_t op0)
enc_o(uint8_t** restrict buf, uint64_t opc, uint64_t epfx, uint64_t op0)
{
if (op_reg_idx(op0) & 0x8) opc |= OPC_REXB;
if (op_reg_idx(op0) & 0x8) epfx |= EPFX_REXB;
bool has_rex = !!(opc & (OPC_REX|OPC_REXW|OPC_REXR|OPC_REXX|OPC_REXB));
bool has_rex = opc & OPC_REXW || epfx & EPFX_REX_MSK;
if (has_rex && op_reg_gph(op0)) return -1;
if (enc_opc(buf, opc)) return -1;
if (enc_opc(buf, opc, epfx)) return -1;
*(*buf - 1) = (*(*buf - 1) & 0xf8) | (op_reg_idx(op0) & 0x7);
return 0;
}
static
int
enc_mr(uint8_t** restrict buf, uint64_t opc, uint64_t op0, uint64_t op1,
unsigned immsz)
enc_mr(uint8_t** restrict buf, uint64_t opc, uint64_t epfx, uint64_t op0,
uint64_t op1, unsigned immsz)
{
// If !op_reg(op1), it is a constant value for ModRM.reg
if (op_reg(op0) && (op_reg_idx(op0) & 0x8)) opc |= OPC_REXB;
if (op_mem(op0) && (op_mem_base(op0) & 0x8)) opc |= OPC_REXB;
if (op_mem(op0) && (op_mem_idx(op0) & 0x8)) opc |= OPC_REXX;
if (op_reg(op1) && op_reg_idx(op1) & 0x8) opc |= OPC_REXR;
if (op_reg(op0) && (op_reg_idx(op0) & 0x8)) epfx |= EPFX_REXB;
if (op_mem(op0) && (op_mem_base(op0) & 0x8)) epfx |= EPFX_REXB;
if (op_mem(op0) && (op_mem_idx(op0) & 0x8)) epfx |= EPFX_REXX;
if (op_reg(op1) && op_reg_idx(op1) & 0x8) epfx |= EPFX_REXR;
bool has_rex = !!(opc & (OPC_REX|OPC_REXW|OPC_REXR|OPC_REXX|OPC_REXB));
bool has_rex = opc & OPC_REXW || epfx & EPFX_REX_MSK;
if (has_rex && (op_reg_gph(op0) || op_reg_gph(op1))) return -1;
unsigned opcsz = opc_size(opc);
unsigned opcsz = opc_size(opc, epfx);
int mod = 0, reg = op1 & 7, rm;
int scale = 0, idx = 4, base = 0;
@@ -246,7 +248,7 @@ enc_mr(uint8_t** restrict buf, uint64_t opc, uint64_t op0, uint64_t op1,
unsigned dispsz = mod == 1 ? 1 : (mod == 2 || mod0off) ? 4 : 0;
if (opcsz + 1 + (mod != 3 && rm == 4) + dispsz + immsz > 15) return -1;
if (enc_opc(buf, opc)) return -1;
if (enc_opc(buf, opc, epfx)) return -1;
*(*buf)++ = (mod << 6) | (reg << 3) | rm;
if (mod != 3 && rm == 4)
*(*buf)++ = (scale << 6) | (idx << 3) | base;
@@ -308,104 +310,86 @@ const struct EncodingInfo encoding_infos[ENC_MAX] = {
[ENC_MRV] = { .modrm = 0^3, .modreg = 1^3, .vexreg = 2^3 },
};
struct EncodeDesc {
uint64_t opc : 26;
uint64_t enc : 5;
uint64_t immsz : 4;
uint64_t alt : 13;
uint64_t tys : 16;
};
static const struct EncodeDesc descs[] = {
static const uint64_t alt_tab[] = {
#include <fadec-encode-private.inc>
};
int
fe_enc64_impl(uint8_t** restrict buf, uint64_t mnem, FeOp op0, FeOp op1,
fe_enc64_impl(uint8_t** restrict buf, uint64_t opc, FeOp op0, FeOp op1,
FeOp op2, FeOp op3)
{
uint8_t* buf_start = *buf;
uint64_t ops[4] = {op0, op1, op2, op3};
uint64_t desc_idx = mnem & FE_MNEM_MASK;
if (UNLIKELY(desc_idx >= FE_MNEM_MAX)) goto fail;
uint64_t epfx = 0;
// Doesn't change between variants
if ((opc & OPC_GPH_OP0) && op_reg_gpl(op0) && op0 >= FE_SP)
epfx |= EPFX_REX;
else if (!(opc & OPC_GPH_OP0) && op_reg_gph(op0))
goto fail;
if ((opc & OPC_GPH_OP1) && op_reg_gpl(op1) && op1 >= FE_SP)
epfx |= EPFX_REX;
else if (!(opc & OPC_GPH_OP1) && op_reg_gph(op1))
goto fail;
do
{
const struct EncodeDesc* desc = &descs[desc_idx];
const struct EncodingInfo* ei = &encoding_infos[desc->enc];
uint64_t opc = desc->opc;
int64_t imm = 0xcc;
unsigned immsz = desc->immsz;
try_encode:;
unsigned enc = (opc >> 51) & 0x1f;
const struct EncodingInfo* ei = &encoding_infos[enc];
if (UNLIKELY(desc->enc == ENC_INVALID)) goto fail;
int64_t imm = 0xcc;
unsigned immsz = (opc >> 47) & 0xf;
if (ei->zregidx)
if (op_reg_idx(ops[ei->zregidx^3]) != ei->zregval) goto next;
if (UNLIKELY(ei->zregidx && op_reg_idx(ops[ei->zregidx^3]) != ei->zregval))
goto next;
for (int i = 0; i < 4; i++) {
unsigned ty = (desc->tys >> (4 * i)) & 0xf;
FeOp op = ops[i];
if (ty == 0x0) continue;
if (ty == 0xf && !op_mem(op)) goto next;
if (ty == 0x1 && !op_reg_gpl(op)) goto next;
if (ty == 0x2 && !op_reg_gpl(op) && !op_reg_gph(op)) goto next;
if (ty == 0x2 && op_reg_gpl(op) && op >= FE_SP) opc |= OPC_REX;
if (ty == 0x3 && !op_reg_seg(op)) goto next;
if (ty == 0x4 && !op_reg_fpu(op)) goto next;
if (ty == 0x5 && !op_reg_mmx(op)) goto next;
if (ty == 0x6 && !op_reg_xmm(op)) goto next;
if (UNLIKELY(ty >= 7 && ty < 0xf)) goto next; // TODO: support BND, CR, DR
if (UNLIKELY(enc == ENC_S)) {
if ((op_reg_idx(op0) << 3 & 0x20) != (opc & 0x20)) goto next;
opc |= op_reg_idx(op0) << 3;
}
if (ei->immctl > 0) {
imm = ops[ei->immidx];
if (ei->immctl == 2) {
immsz = UNLIKELY(opc & OPC_67) ? 4 : 8;
if (immsz == 4) imm = (int32_t) imm; // address are zero-extended
}
if (UNLIKELY(mnem & FE_ADDR32))
opc |= OPC_67;
if (UNLIKELY(mnem & FE_SEG_MASK))
opc |= (mnem & FE_SEG_MASK) << (OPC_SEG_IDX - 16);
if (UNLIKELY(desc->enc == ENC_S)) {
if ((op_reg_idx(op0) << 3 & 0x20) != (opc & 0x20)) goto next;
opc |= op_reg_idx(op0) << 3;
if (ei->immctl == 3) {
if (!op_reg_xmm(imm)) goto fail;
imm = op_reg_idx(imm) << 4;
}
if (ei->immctl > 0) {
imm = ops[ei->immidx];
if (ei->immctl == 2) {
immsz = UNLIKELY(mnem & FE_ADDR32) ? 4 : 8;
if (immsz == 4) imm = (int32_t) imm; // address are zero-extended
}
if (ei->immctl == 3)
imm = op_reg_idx(imm) << 4;
if (ei->immctl == 6) {
if (UNLIKELY(mnem & FE_JMPL) && desc->alt) goto next;
imm -= (int64_t) *buf + opc_size(opc) + immsz;
}
if (UNLIKELY(ei->immctl == 1) && imm != 1) goto next;
if (ei->immctl >= 2 && !op_imm_n(imm, immsz)) goto next;
if (ei->immctl == 6) {
if (UNLIKELY(opc & FE_JMPL) && opc >> 56) goto next;
imm -= (int64_t) *buf + opc_size(opc, epfx) + immsz;
}
if (UNLIKELY(ei->immctl == 1) && imm != 1) goto next;
if (ei->immctl >= 2 && !op_imm_n(imm, immsz)) goto next;
}
// NOP has no operands, so this must be the 32-bit OA XCHG
if ((desc->opc & ~7) == 0x90 && ops[0] == FE_AX) goto next;
// NOP has no operands, so this must be the 32-bit OA XCHG
if ((opc & 0xfffffff) == 0x90 && ops[0] == FE_AX) goto next;
if (ei->modrm) {
FeOp modreg = ei->modreg ? ops[ei->modreg^3] : (opc & 0xff00) >> 8;
if (ei->vexreg)
opc |= ((uint64_t) op_reg_idx(ops[ei->vexreg^3])) << OPC_VEXOP_IDX;
epfx |= ((uint64_t) op_reg_idx(ops[ei->vexreg^3])) << EPFX_VVVV_IDX;
if (enc_mr(buf, opc, epfx, ops[ei->modrm^3], modreg, immsz)) goto fail;
} else if (ei->modreg) {
if (enc_o(buf, opc, epfx, ops[ei->modreg^3])) goto fail;
} else {
if (enc_opc(buf, opc, epfx)) goto fail;
}
if (ei->modrm) {
FeOp modreg = ei->modreg ? ops[ei->modreg^3] : (opc & 0xff00) >> 8;
if (enc_mr(buf, opc, ops[ei->modrm^3], modreg, immsz)) goto fail;
} else if (ei->modreg) {
if (enc_o(buf, opc, ops[ei->modreg^3])) goto fail;
} else {
if (enc_opc(buf, opc)) goto fail;
}
if (ei->immctl >= 2)
if (enc_imm(buf, imm, immsz)) goto fail;
if (ei->immctl >= 2)
if (enc_imm(buf, imm, immsz)) goto fail;
return 0;
return 0;
next:
desc_idx = desc->alt;
} while (desc_idx != 0);
next:;
uint64_t alt = opc >> 56;
if (alt) { // try alternative encoding, if available
opc = alt_tab[alt] | (opc & OPC_USER_MSK);
goto try_encode;
}
fail:
// Don't advance buffer on error; though we shouldn't write anything.