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Add array bounds check elimination (-Oabc, on by default).

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This commit is contained in:
Mike Pall
2010-03-15 17:02:53 +01:00
parent 24402ede04
commit c4727220e8
5 changed files with 100 additions and 19 deletions
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65
src/lj_opt_fold.c
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@@ -1,5 +1,6 @@
/*
** FOLD: Constant Folding, Algebraic Simplifications and Reassociation.
** ABCelim: Array Bounds Check Elimination.
** CSE: Common-Subexpression Elimination.
** Copyright (C) 2005-2010 Mike Pall. See Copyright Notice in luajit.h
*/
@@ -949,31 +950,69 @@ LJFOLDF(reassoc_minmax_right)
return NEXTFOLD;
}
/* -- Array bounds check elimination -------------------------------------- */
/* Eliminate ABC across PHIs to handle t[i-1] forwarding case.
** ABC(asize, (i+k)+(-k)) ==> ABC(asize, i), but only if it already exists.
** Could be generalized to (i+k1)+k2 ==> i+(k1+k2), but needs better disambig.
*/
LJFOLD(ABC any ADD)
LJFOLDF(reassoc_abc)
LJFOLDF(abc_fwd)
{
if (irref_isk(fright->op2)) {
IRIns *add2 = IR(fright->op1);
if (add2->o == IR_ADD && irref_isk(add2->op2) &&
IR(fright->op2)->i == -IR(add2->op2)->i) {
IRRef ref = J->chain[IR_ABC];
IRRef lim = add2->op1;
if (fins->op1 > lim) lim = fins->op1;
while (ref > lim) {
IRIns *ir = IR(ref);
if (ir->op1 == fins->op1 && ir->op2 == add2->op1)
return DROPFOLD;
ref = ir->prev;
if (LJ_LIKELY(J->flags & JIT_F_OPT_ABC)) {
if (irref_isk(fright->op2)) {
IRIns *add2 = IR(fright->op1);
if (add2->o == IR_ADD && irref_isk(add2->op2) &&
IR(fright->op2)->i == -IR(add2->op2)->i) {
IRRef ref = J->chain[IR_ABC];
IRRef lim = add2->op1;
if (fins->op1 > lim) lim = fins->op1;
while (ref > lim) {
IRIns *ir = IR(ref);
if (ir->op1 == fins->op1 && ir->op2 == add2->op1)
return DROPFOLD;
ref = ir->prev;
}
}
}
}
return NEXTFOLD;
}
/* Eliminate ABC for constants.
** ABC(asize, k1), ABC(asize k2) ==> ABC(asize, max(k1, k2))
** Drop second ABC if k2 is lower. Otherwise patch first ABC with k2.
*/
LJFOLD(ABC any KINT)
LJFOLDF(abc_k)
{
if (LJ_LIKELY(J->flags & JIT_F_OPT_ABC)) {
IRRef ref = J->chain[IR_ABC];
IRRef asize = fins->op1;
while (ref > asize) {
IRIns *ir = IR(ref);
if (ir->op1 == asize && irref_isk(ir->op2)) {
int32_t k = IR(ir->op2)->i;
if (fright->i > k)
ir->op2 = fins->op2;
return DROPFOLD;
}
ref = ir->prev;
}
return EMITFOLD; /* Already performed CSE. */
}
return NEXTFOLD;
}
/* Eliminate invariant ABC inside loop. */
LJFOLD(ABC any any)
LJFOLDF(abc_invar)
{
if (!irt_isint(fins->t) && J->chain[IR_LOOP]) /* Currently marked as PTR. */
return DROPFOLD;
return NEXTFOLD;
}
/* -- Commutativity ------------------------------------------------------- */
/* The refs of commutative ops are canonicalized. Lower refs go to the right.