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decode: Minor performance improvements

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This commit is contained in:
Alexis Engelke
2020-11-27 09:07:52 +01:00
parent fd80706f54
commit 757acf18c3
1 changed files with 10 additions and 8 deletions
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18
decode.c
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@@ -128,24 +128,26 @@ decode_modrm(const uint8_t* buffer, int len, DecodeMode mode, FdInstr* instr,
return FD_ERR_UD;
// SIB byte
uint8_t scale = 0;
uint8_t idx = 4;
uint8_t base = rm;
if (rm == 4)
{
if (UNLIKELY(off >= len))
return FD_ERR_PARTIAL;
uint8_t sib = buffer[off++];
scale = (sib & 0xc0) >> 6;
idx = (sib & 0x38) >> 3;
unsigned scale = (sib & 0xc0) >> 6;
unsigned idx = (sib & 0x38) >> 3;
#if defined(ARCH_X86_64)
idx += prefixes & PREFIX_REXX ? 8 : 0;
#endif
base = sib & 0x07;
out_o1->misc = (scale << 6) | (!vsib && idx == 4 ? FD_REG_NONE : idx);
}
else
{
out_o1->misc = FD_REG_NONE;
}
out_o1->type = FD_OT_MEM;
out_o1->misc = (scale << 6) | (!vsib && idx == 4 ? FD_REG_NONE : idx);
// RIP-relative addressing only if SIB-byte is absent
if (mod == 0 && rm == 5 && mode == DECODE_64)
@@ -399,8 +401,6 @@ prefix_end:
instr->type = desc->type;
instr->flags = prefix_rep == 2 ? FD_FLAG_REP :
prefix_rep == 3 ? FD_FLAG_REPNZ : 0;
if (prefix_lock)
instr->flags |= FD_FLAG_LOCK;
if (mode == DECODE_64)
instr->flags |= FD_FLAG_64;
instr->address = address;
@@ -588,9 +588,11 @@ prefix_end:
}
}
if (UNLIKELY(prefix_lock))
if (UNLIKELY(prefix_lock)) {
if (!DESC_LOCK(desc) || instr->operands[0].type != FD_OT_MEM)
return FD_ERR_UD;
instr->flags |= FD_FLAG_LOCK;
}
uint8_t operand_sizes[4] = {
1 << DESC_SIZE_FIX1(desc) >> 1, 1 << DESC_SIZE_FIX2(desc), op_size, vec_size