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