* [Qemu-devel] What do these instructions do??
@ 2012-04-05 20:14 Davide
2012-04-05 22:06 ` Max Filippov
0 siblings, 1 reply; 2+ messages in thread
From: Davide @ 2012-04-05 20:14 UTC (permalink / raw)
To: qemu-devel
In target-i386/translate.c there are this instructions:
int op, f, val;
op = (b >> 3) & 7;
f = (b >> 1) & 3;
if ((b & 1) == 0)
ot = OT_BYTE;
else
ot = dflag + OT_WORD;
What does this code do??
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: [Qemu-devel] What do these instructions do?? 2012-04-05 20:14 [Qemu-devel] What do these instructions do?? Davide @ 2012-04-05 22:06 ` Max Filippov 0 siblings, 0 replies; 2+ messages in thread From: Max Filippov @ 2012-04-05 22:06 UTC (permalink / raw) To: Davide; +Cc: qemu-devel > In target-i386/translate.c there are this instructions: > int op, f, val; > op = (b >> 3) & 7; > f = (b >> 1) & 3; > if ((b & 1) == 0) > ot = OT_BYTE; > else > ot = dflag + OT_WORD; > What does this code do?? It extracts some useful subfields from one-byte opcodes, e.g. op is the arithmetic operation code, f is operand encoding and ot is operand width. Table A2 in the Intel® 64 and IA-32 Architectures Developer's Manual: Vol. 2B http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-2b-manual.html will probably help. -- Thanks. -- Max ^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2012-04-05 22:06 UTC | newest] Thread overview: 2+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-04-05 20:14 [Qemu-devel] What do these instructions do?? Davide 2012-04-05 22:06 ` Max Filippov
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.