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Randomize penalties for aborts and add blacklisting.

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This commit is contained in:
Mike Pall
2010-02-23 18:27:39 +01:00
parent d5c8fe4b90
commit 8ae2f9feaa
6 changed files with 50 additions and 23 deletions
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42
src/lj_trace.c
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@@ -294,27 +294,50 @@ void lj_trace_freestate(global_State *g)
lj_mem_freevec(g, J->trace, J->sizetrace, Trace *);
}
/* -- Trace compiler state machine ---------------------------------------- */
/* -- Penalties and blacklisting ------------------------------------------ */
/* Penalize a bytecode instruction by bumping its hot counter. */
static void hotpenalty(jit_State *J, const BCIns *pc, TraceError e)
/* Trivial PRNG for randomization of penalties. */
static uint32_t penalty_prng(jit_State *J, int bits)
{
uint32_t i, val = HOTCOUNT_MIN_PENALTY;
/* Yes, this LCG is very weak, but that doesn't matter for our use case. */
J->prngstate = J->prngstate * 1103515245 + 12345;
return J->prngstate >> (32-bits);
}
/* Blacklist a bytecode instruction. */
static void blacklist_pc(GCproto *pt, BCIns *pc)
{
setbc_op(pc, (int)bc_op(*pc)+(int)BC_ILOOP-(int)BC_LOOP);
pt->flags |= PROTO_HAS_ILOOP;
}
/* Penalize a bytecode instruction. */
static void penalty_pc(jit_State *J, GCproto *pt, BCIns *pc, TraceError e)
{
uint32_t i, val = PENALTY_MIN;
for (i = 0; i < PENALTY_SLOTS; i++)
if (J->penalty[i].pc == pc) {
val = ((uint32_t)J->penalty[i].val << 1) + 1;
if (val > HOTCOUNT_MAX_PENALTY) val = HOTCOUNT_MAX_PENALTY;
if (mref(J->penalty[i].pc, const BCIns) == pc) { /* Cache slot found? */
/* First try to bump its hotcount several times. */
val = ((uint32_t)J->penalty[i].val << 1) +
penalty_prng(J, PENALTY_RNDBITS);
if (val > PENALTY_MAX) {
blacklist_pc(pt, pc); /* Blacklist it, if that didn't help. */
return;
}
goto setpenalty;
}
/* Assign a new penalty cache slot. */
i = J->penaltyslot;
J->penaltyslot = (J->penaltyslot + 1) & (PENALTY_SLOTS-1);
J->penalty[i].pc = pc;
setmref(J->penalty[i].pc, pc);
setpenalty:
J->penalty[i].val = (uint16_t)val;
J->penalty[i].reason = e;
hotcount_set(J2GG(J), pc+1, val);
}
/* -- Trace compiler state machine ---------------------------------------- */
/* Start tracing. */
static void trace_start(jit_State *J)
{
@@ -433,8 +456,9 @@ static int trace_abort(jit_State *J)
J->state = LJ_TRACE_ASM;
return 1; /* Retry ASM with new MCode area. */
}
/* Penalize or blacklist starting bytecode instruction. */
if (J->parent == 0)
hotpenalty(J, J->startpc, e); /* Penalize starting instruction. */
penalty_pc(J, &gcref(J->cur.startpt)->pt, (BCIns *)J->startpc, e);
if (J->curtrace) { /* Is there anything to abort? */
ptrdiff_t errobj = savestack(L, L->top-1); /* Stack may be resized. */
lj_vmevent_send(L, TRACE,