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Improve Cyrix 6x86 prefix timing.

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This commit is contained in:
SarahW 2018-03-24 16:58:45 +00:00
commit 1b7a821eff
1 changed files with 15 additions and 1 deletions
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14
src/codegen_timing_686.c
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@ -785,6 +785,18 @@ void codegen_timing_686_start()
void codegen_timing_686_prefix(uint8_t prefix, uint32_t fetchdat) void codegen_timing_686_prefix(uint8_t prefix, uint32_t fetchdat)
{ {
if ((prefix & 0xf8) == 0xd8)
{
last_prefix = prefix;
return;
}
if (prefix == 0x0f && (fetchdat & 0xf0) == 0x80)
{
/*0fh prefix is 'free' when used on conditional jumps*/
last_prefix = prefix;
return;
}
/*6x86 can decode 1 prefix per instruction per clock with no penalty. If /*6x86 can decode 1 prefix per instruction per clock with no penalty. If
either instruction has more than one prefix then decode is delayed by either instruction has more than one prefix then decode is delayed by
one cycle for each additional prefix*/ one cycle for each additional prefix*/
@ -939,6 +951,8 @@ void codegen_timing_686_opcode(uint8_t opcode, uint32_t fetchdat, int op_32)
} }
} }
/*One prefix per instruction is free*/
decode_delay--;
if (decode_delay < 0) if (decode_delay < 0)
decode_delay = 0; decode_delay = 0;