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Make penalty PRNG available for general use by compiler.

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Mike Pall 2010-02-26 17:01:33 +01:00
parent 3c6cec0846
commit a0fbb05bf0
2 changed files with 10 additions and 10 deletions
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10
src/lj_jit.h
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@ -278,7 +278,7 @@ typedef struct jit_State {
HotPenalty penalty[PENALTY_SLOTS]; /* Penalty slots. */ HotPenalty penalty[PENALTY_SLOTS]; /* Penalty slots. */
uint32_t penaltyslot; /* Round-robin index into penalty slots. */ uint32_t penaltyslot; /* Round-robin index into penalty slots. */
uint32_t prngstate; /* PRNG state for penalty randomization. */ uint32_t prngstate; /* PRNG state. */
BPropEntry bpropcache[BPROP_SLOTS]; /* Backpropagation cache slots. */ BPropEntry bpropcache[BPROP_SLOTS]; /* Backpropagation cache slots. */
uint32_t bpropslot; /* Round-robin index into bpropcache slots. */ uint32_t bpropslot; /* Round-robin index into bpropcache slots. */
@ -297,6 +297,14 @@ typedef struct jit_State {
int mcprot; /* Protection of current mcode area. */ int mcprot; /* Protection of current mcode area. */
} jit_State; } jit_State;
/* Trivial PRNG e.g. used for penalty randomization. */
static LJ_AINLINE uint32_t LJ_PRNG_BITS(jit_State *J, int bits)
{
/* 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);
}
/* Exit stubs. */ /* Exit stubs. */
#if LJ_TARGET_X86ORX64 #if LJ_TARGET_X86ORX64
/* Limited by the range of a short fwd jump (127): (2+2)*(32-1)-2 = 122. */ /* Limited by the range of a short fwd jump (127): (2+2)*(32-1)-2 = 122. */

10
src/lj_trace.c
View File

@ -310,14 +310,6 @@ void lj_trace_freestate(global_State *g)
/* -- Penalties and blacklisting ------------------------------------------ */ /* -- Penalties and blacklisting ------------------------------------------ */
/* Trivial PRNG for randomization of penalties. */
static uint32_t penalty_prng(jit_State *J, int bits)
{
/* 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. */ /* Blacklist a bytecode instruction. */
static void blacklist_pc(GCproto *pt, BCIns *pc) static void blacklist_pc(GCproto *pt, BCIns *pc)
{ {
@ -333,7 +325,7 @@ static void penalty_pc(jit_State *J, GCproto *pt, BCIns *pc, TraceError e)
if (mref(J->penalty[i].pc, const BCIns) == pc) { /* Cache slot found? */ if (mref(J->penalty[i].pc, const BCIns) == pc) { /* Cache slot found? */
/* First try to bump its hotcount several times. */ /* First try to bump its hotcount several times. */
val = ((uint32_t)J->penalty[i].val << 1) + val = ((uint32_t)J->penalty[i].val << 1) +
penalty_prng(J, PENALTY_RNDBITS); LJ_PRNG_BITS(J, PENALTY_RNDBITS);
if (val > PENALTY_MAX) { if (val > PENALTY_MAX) {
blacklist_pc(pt, pc); /* Blacklist it, if that didn't help. */ blacklist_pc(pt, pc); /* Blacklist it, if that didn't help. */
return; return;