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Improve alias analysis for cdata allocations.

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This commit is contained in:
Mike Pall 2010-12-20 15:26:05 +01:00
parent 255c6e8c87
commit c9a0b9ea9e
1 changed files with 43 additions and 15 deletions
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58
src/lj_opt_mem.c
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@ -37,10 +37,22 @@ typedef enum {
/* -- ALOAD/HLOAD forwarding and ASTORE/HSTORE elimination ---------------- */
/* Simplified escape analysis: check for intervening stores. */
static AliasRet aa_escape(jit_State *J, IRIns *ir, IRIns *stop)
{
IRRef ref = ir - J->cur.ir; /* The reference that might be stored. */
for (ir++; ir < stop; ir++)
if (ir->op2 == ref &&
(ir->o == IR_ASTORE || ir->o == IR_HSTORE ||
ir->o == IR_USTORE || ir->o == IR_FSTORE))
return ALIAS_MAY; /* Reference was stored and might alias. */
return ALIAS_NO; /* Reference was not stored. */
}
/* Alias analysis for two different table references. */
static AliasRet aa_table(jit_State *J, IRRef ta, IRRef tb)
{
IRIns *ir, *taba = IR(ta), *tabb = IR(tb);
IRIns *taba = IR(ta), *tabb = IR(tb);
int newa, newb;
lua_assert(ta != tb);
lua_assert(irt_istab(taba->t) && irt_istab(tabb->t));
@ -50,21 +62,11 @@ static AliasRet aa_table(jit_State *J, IRRef ta, IRRef tb)
if (newa && newb)
return ALIAS_NO; /* Two different allocations never alias. */
if (newb) { /* At least one allocation? */
IRRef tmp = ta; ta = tb; tb = tmp;
IRIns *tmp = taba; taba = tabb; tabb = tmp;
} else if (!newa) {
return ALIAS_MAY; /* Anything else: we just don't know. */
}
/* Now ta holds the allocation, tb the other table reference.
** The allocation might be stored and reloaded as tb. So perform a
** simplified escape analysis: check for intervening stores which have
** the allocation as the right operand.
*/
for (ir = IR(ta+1); ir < IR(tb); ir++)
if (ir->op2 == ta &&
(ir->o == IR_ASTORE || ir->o == IR_HSTORE ||
ir->o == IR_USTORE || ir->o == IR_FSTORE))
return ALIAS_MAY; /* Allocation was stored and might alias. */
return ALIAS_NO; /* Allocation doesn't alias the other reference. */
return aa_escape(J, taba, tabb);
}
/* Alias analysis for array and hash access using key-based disambiguation. */
@ -525,6 +527,33 @@ doemit:
/* -- XLOAD forwarding and XSTORE elimination ----------------------------- */
/* Find cdata allocation for a reference (if any). */
static IRIns *aa_findcnew(jit_State *J, IRIns *ir)
{
while (ir->o == IR_ADD) {
if (!irref_isk(ir->op1)) {
IRIns *ir1 = aa_findcnew(J, IR(ir->op1)); /* Left-recursion. */
if (ir1) return ir1;
}
if (irref_isk(ir->op2)) return NULL;
ir = IR(ir->op2); /* Flatten right-recursion. */
}
return ir->o == IR_CNEW ? ir : NULL;
}
/* Alias analysis for two cdata allocations. */
static AliasRet aa_cnew(jit_State *J, IRIns *refa, IRIns *refb)
{
IRIns *cnewa = aa_findcnew(J, refa);
IRIns *cnewb = aa_findcnew(J, refb);
if (cnewa == cnewb)
return ALIAS_MAY; /* Same allocation or neither is an allocation. */
if (cnewa && cnewb)
return ALIAS_NO; /* Two different allocations never alias. */
if (cnewb) { cnewa = cnewb; refb = refa; }
return aa_escape(J, cnewa, refb);
}
/* Alias analysis for XLOAD/XSTORE. */
static AliasRet aa_xref(jit_State *J, IRIns *xa, IRIns *xb)
{
@ -570,8 +599,7 @@ static AliasRet aa_xref(jit_State *J, IRIns *xa, IRIns *xb)
return ALIAS_MAY;
}
/* NYI: structural disambiguation. */
/* NYI: disambiguate new allocations. */
return ALIAS_MAY;
return aa_cnew(J, basea, baseb); /* Try to disambiguate allocations. */
}
/* XLOAD forwarding. */