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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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2
doc/running.html
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@ -181,6 +181,8 @@ are enabled:
<tr class="odd">
<td class="flag_name">dse</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Dead-Store Elimination</td></tr>
<tr class="even">
<td class="flag_name">abc</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Array Bounds Check Elimination</td></tr>
<tr class="odd">
<td class="flag_name">fuse</td><td class="flag_level">&nbsp;</td><td class="flag_level">&nbsp;</td><td class="flag_level">&bull;</td><td class="flag_desc">Fusion of operands into instructions</td></tr>
</table>
<p>

2
src/lj_asm.c
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@ -2571,7 +2571,7 @@ static void asm_comp_(ASMState *as, IRIns *ir, int cc)
} else {
IRRef lref = ir->op1, rref = ir->op2;
IROp leftop = (IROp)(IR(lref)->o);
lua_assert(irt_isint(ir->t) || (irt_isaddr(ir->t) && (cc & 0xe) == CC_E));
lua_assert(irt_isint(ir->t) || irt_isaddr(ir->t));
/* Swap constants (only for ABC) and fusable loads to the right. */
if (irref_isk(lref) || (!irref_isk(rref) && opisfusableload(leftop))) {
if ((cc & 0xc) == 0xc) cc ^= 3; /* L <-> G, LE <-> GE */

10
src/lj_jit.h
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@ -30,7 +30,7 @@
#endif
/* Optimization flags. */
#define JIT_F_OPT_MASK 0x00ff0000
#define JIT_F_OPT_MASK 0x0fff0000
#define JIT_F_OPT_FOLD 0x00010000
#define JIT_F_OPT_CSE 0x00020000
@ -39,18 +39,20 @@
#define JIT_F_OPT_DSE 0x00100000
#define JIT_F_OPT_NARROW 0x00200000
#define JIT_F_OPT_LOOP 0x00400000
#define JIT_F_OPT_FUSE 0x00800000
#define JIT_F_OPT_ABC 0x00800000
#define JIT_F_OPT_FUSE 0x01000000
/* Optimizations names for -O. Must match the order above. */
#define JIT_F_OPT_FIRST JIT_F_OPT_FOLD
#define JIT_F_OPTSTRING \
"\4fold\3cse\3dce\3fwd\3dse\6narrow\4loop\4fuse"
"\4fold\3cse\3dce\3fwd\3dse\6narrow\4loop\3abc\4fuse"
/* Optimization levels set a fixed combination of flags. */
#define JIT_F_OPT_0 0
#define JIT_F_OPT_1 (JIT_F_OPT_FOLD|JIT_F_OPT_CSE|JIT_F_OPT_DCE)
#define JIT_F_OPT_2 (JIT_F_OPT_1|JIT_F_OPT_NARROW|JIT_F_OPT_LOOP)
#define JIT_F_OPT_3 (JIT_F_OPT_2|JIT_F_OPT_FWD|JIT_F_OPT_DSE|JIT_F_OPT_FUSE)
#define JIT_F_OPT_3 \
(JIT_F_OPT_2|JIT_F_OPT_FWD|JIT_F_OPT_DSE|JIT_F_OPT_ABC|JIT_F_OPT_FUSE)
#define JIT_F_OPT_DEFAULT JIT_F_OPT_3
#if defined(LUA_USE_WIN) || LJ_64

41
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
*/
@ -949,13 +950,16 @@ 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 (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) &&
@ -971,6 +975,41 @@ LJFOLDF(reassoc_abc)
}
}
}
}
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;
}

40
src/lj_record.c
View File

@ -806,6 +806,44 @@ static void rec_mm_comp(jit_State *J, RecordIndex *ix, int op)
/* -- Indexed access ------------------------------------------------------ */
/* Record bounds-check. */
static void rec_idx_abc(jit_State *J, TRef asizeref, TRef ikey, uint32_t asize)
{
/* Try to emit invariant bounds checks. */
if ((J->flags & (JIT_F_OPT_LOOP|JIT_F_OPT_ABC)) ==
(JIT_F_OPT_LOOP|JIT_F_OPT_ABC)) {
IRRef ref = tref_ref(ikey);
IRIns *ir = IR(ref);
int32_t ofs = 0;
IRRef ofsref = 0;
/* Handle constant offsets. */
if (ir->o == IR_ADD && irref_isk(ir->op2)) {
ofsref = ir->op2;
ofs = IR(ofsref)->i;
ref = ir->op1;
ir = IR(ref);
}
/* Got scalar evolution analysis results for this reference? */
if (ref == J->scev.idx) {
int32_t stop;
lua_assert(irt_isint(J->scev.t) && ir->o == IR_SLOAD);
stop = lj_num2int(numV(&(J->L->base - J->baseslot)[ir->op1 + FORL_STOP]));
/* Runtime value for stop of loop is within bounds? */
if ((int64_t)stop + ofs < (int64_t)asize) {
/* Emit invariant bounds check for stop. */
emitir(IRTG(IR_ABC, IRT_PTR), asizeref, ofs == 0 ? J->scev.stop :
emitir(IRTI(IR_ADD), J->scev.stop, ofsref));
/* Emit invariant bounds check for start, if not const or negative. */
if (!(J->scev.dir && J->scev.start &&
(int64_t)IR(J->scev.start)->i + ofs >= 0))
emitir(IRTG(IR_ABC, IRT_PTR), asizeref, ikey);
return;
}
}
}
emitir(IRTGI(IR_ABC), asizeref, ikey); /* Emit regular bounds check. */
}
/* Record indexed key lookup. */
static TRef rec_idx_key(jit_State *J, RecordIndex *ix)
{
@ -827,7 +865,7 @@ static TRef rec_idx_key(jit_State *J, RecordIndex *ix)
asizeref = emitir(IRTI(IR_FLOAD), ix->tab, IRFL_TAB_ASIZE);
if ((MSize)k < t->asize) { /* Currently an array key? */
TRef arrayref;
emitir(IRTGI(IR_ABC), asizeref, ikey); /* Bounds check. */
rec_idx_abc(J, asizeref, ikey, t->asize);
arrayref = emitir(IRT(IR_FLOAD, IRT_PTR), ix->tab, IRFL_TAB_ARRAY);
return emitir(IRT(IR_AREF, IRT_PTR), arrayref, ikey);
} else { /* Currently not in array (may be an array extension)? */