/* Alias analysis for XLOAD/XSTORE. */ static AliasRet aa_xref(jit_State *J, IRIns *refa, IRIns *xa, IRIns *xb) { ptrdiff_t ofsa = 0, ofsb = 0; IRIns *refb = IR(xb->op1); IRIns *basea = refa, *baseb = refb; if (refa == refb && irt_sametype(xa->t, xb->t)) return ALIAS_MUST; /* Shortcut for same refs with identical type. */ /* Offset-based disambiguation. */ if (refa->o == IR_ADD && irref_isk(refa->op2)) { IRIns *irk = IR(refa->op2); basea = IR(refa->op1); ofsa = (LJ_64 && irk->o == IR_KINT64) ? (ptrdiff_t)ir_k64(irk)->u64 : (ptrdiff_t)irk->i; } if (refb->o == IR_ADD && irref_isk(refb->op2)) { IRIns *irk = IR(refb->op2); baseb = IR(refb->op1); ofsb = (LJ_64 && irk->o == IR_KINT64) ? (ptrdiff_t)ir_k64(irk)->u64 : (ptrdiff_t)irk->i; } /* Treat constified pointers like base vs. base+offset. */ if (basea->o == IR_KPTR && baseb->o == IR_KPTR) { ofsb += (char *)ir_kptr(baseb) - (char *)ir_kptr(basea); baseb = basea; } /* This implements (very) strict aliasing rules. ** Different types do NOT alias, except for differences in signedness. ** Type punning through unions is allowed (but forces a reload). */ if (basea == baseb) { ptrdiff_t sza = irt_size(xa->t), szb = irt_size(xb->t); if (ofsa == ofsb) { if (sza == szb && irt_isfp(xa->t) == irt_isfp(xb->t)) return ALIAS_MUST; /* Same-sized, same-kind. May need to convert. */ } else if (ofsa + sza <= ofsb || ofsb + szb <= ofsa) { return ALIAS_NO; /* Non-overlapping base+-o1 vs. base+-o2. */ } /* NYI: extract, extend or reinterpret bits (int <-> fp). */ return ALIAS_MAY; /* Overlapping or type punning: force reload. */ } if (!irt_sametype(xa->t, xb->t) && !(irt_typerange(xa->t, IRT_I8, IRT_U64) && ((xa->t.irt - IRT_I8) ^ (xb->t.irt - IRT_I8)) == 1)) return ALIAS_NO; /* NYI: structural disambiguation. */ return aa_cnew(J, basea, baseb); /* Try to disambiguate allocations. */ }
/* Alias analysis for XLOAD/XSTORE. */ static AliasRet aa_xref(jit_State *J, IRIns *refa, IRIns *xa, IRIns *xb) { ptrdiff_t ofsa = 0, ofsb = 0; IRIns *refb = IR(xb->op1); IRIns *basea = refa, *baseb = refb; /* 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(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_U64) && ((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); basea = IR(refa->op1); ofsa = (LJ_64 && irk->o == IR_KINT64) ? (ptrdiff_t)ir_k64(irk)->u64 : (ptrdiff_t)irk->i; if (basea == refb && ofsa != 0) return ALIAS_NO; /* base+-ofs vs. base. */ } if (refb->o == IR_ADD && irref_isk(refb->op2)) { IRIns *irk = IR(refb->op2); baseb = IR(refb->op1); ofsb = (LJ_64 && irk->o == IR_KINT64) ? (ptrdiff_t)ir_k64(irk)->u64 : (ptrdiff_t)irk->i; if (refa == baseb && ofsb != 0) return ALIAS_NO; /* base vs. base+-ofs. */ } if (basea == baseb) { /* This assumes strictly-typed, non-overlapping accesses. */ if (ofsa != ofsb) return ALIAS_NO; /* base+-o1 vs. base+-o2 and o1 != o2. */ return ALIAS_MUST; /* Unsigned vs. signed access to the same address. */ } /* NYI: structural disambiguation. */ return aa_cnew(J, basea, baseb); /* Try to disambiguate allocations. */ }