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Fix type-based alias analysis for XLOAD/XSTORE.

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Mike Pall 2010-12-12 23:09:26 +01:00
parent 74317fa0ef
commit 9666cf52ce
1 changed files with 10 additions and 10 deletions
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20
src/lj_opt_mem.c
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@ -526,20 +526,22 @@ doemit:
/* -- XLOAD forwarding and XSTORE elimination ----------------------------- */
/* Alias analysis for XLOAD/XSTORE. */
static AliasRet aa_xref(jit_State *J, IRIns *refa, IRIns *refb)
static AliasRet aa_xref(jit_State *J, IRIns *xa, IRIns *xb)
{
ptrdiff_t ofsa = 0, ofsb = 0;
IRIns *refa = IR(xa->op1), *refb = IR(xb->op1);
IRIns *basea = refa, *baseb = refb;
if (refa == refb)
return ALIAS_MUST; /* Shortcut for same refs. */
/* This implements (very) strict aliasing rules.
** Different types do NOT alias, except for differences in signedness.
** NYI: this also prevents type punning through unions.
*/
if (!(irt_sametype(refa->t, refb->t) ||
(irt_typerange(refa->t, IRT_I8, IRT_INT) &&
((refa->t.irt - IRT_I8) ^ (refb->t.irt - IRT_I8)) == 1)))
if (irt_sametype(xa->t, xb->t)) {
if (refa == refb)
return ALIAS_MUST; /* Shortcut for same refs with identical type. */
} else if (!(irt_typerange(xa->t, IRT_I8, IRT_INT) &&
((xa->t.irt - IRT_I8) ^ (xb->t.irt - IRT_I8)) == 1)) {
return ALIAS_NO;
}
/* Offset-based disambiguation. */
if (refa->o == IR_ADD && irref_isk(refa->op2)) {
IRIns *irk = IR(refa->op2);
@ -577,7 +579,6 @@ TRef LJ_FASTCALL lj_opt_fwd_xload(jit_State *J)
{
IRRef xref = fins->op1;
IRRef lim = xref; /* Search limit. */
IRIns *xr = IR(xref);
IRRef ref;
if ((fins->op2 & IRXLOAD_READONLY))
@ -587,7 +588,7 @@ TRef LJ_FASTCALL lj_opt_fwd_xload(jit_State *J)
ref = J->chain[IR_XSTORE];
while (ref > xref) {
IRIns *store = IR(ref);
switch (aa_xref(J, xr, IR(store->op1))) {
switch (aa_xref(J, fins, store)) {
case ALIAS_NO: break; /* Continue searching. */
case ALIAS_MAY: lim = ref; goto cselim; /* Limit search for load. */
case ALIAS_MUST: return store->op2; /* Store forwarding. */
@ -612,12 +613,11 @@ TRef LJ_FASTCALL lj_opt_dse_xstore(jit_State *J)
{
IRRef xref = fins->op1;
IRRef val = fins->op2; /* Stored value reference. */
IRIns *xr = IR(xref);
IRRef1 *refp = &J->chain[IR_XSTORE];
IRRef ref = *refp;
while (ref > xref) { /* Search for redundant or conflicting stores. */
IRIns *store = IR(ref);
switch (aa_xref(J, xr, IR(store->op1))) {
switch (aa_xref(J, fins, store)) {
case ALIAS_NO:
break; /* Continue searching. */
case ALIAS_MAY: