diff options
Diffstat (limited to 'libs/luajit-cmake/luajit/src/lj_opt_mem.c')
| -rw-r--r-- | libs/luajit-cmake/luajit/src/lj_opt_mem.c | 979 |
1 files changed, 979 insertions, 0 deletions
diff --git a/libs/luajit-cmake/luajit/src/lj_opt_mem.c b/libs/luajit-cmake/luajit/src/lj_opt_mem.c new file mode 100644 index 0000000..09de2f0 --- /dev/null +++ b/libs/luajit-cmake/luajit/src/lj_opt_mem.c @@ -0,0 +1,979 @@ +/* +** Memory access optimizations. +** AA: Alias Analysis using high-level semantic disambiguation. +** FWD: Load Forwarding (L2L) + Store Forwarding (S2L). +** DSE: Dead-Store Elimination. +** Copyright (C) 2005-2022 Mike Pall. See Copyright Notice in luajit.h +*/ + +#define lj_opt_mem_c +#define LUA_CORE + +#include "lj_obj.h" + +#if LJ_HASJIT + +#include "lj_tab.h" +#include "lj_ir.h" +#include "lj_jit.h" +#include "lj_iropt.h" +#include "lj_ircall.h" +#include "lj_dispatch.h" + +/* Some local macros to save typing. Undef'd at the end. */ +#define IR(ref) (&J->cur.ir[(ref)]) +#define fins (&J->fold.ins) +#define fleft (J->fold.left) +#define fright (J->fold.right) + +/* +** Caveat #1: return value is not always a TRef -- only use with tref_ref(). +** Caveat #2: FWD relies on active CSE for xREF operands -- see lj_opt_fold(). +*/ + +/* Return values from alias analysis. */ +typedef enum { + ALIAS_NO, /* The two refs CANNOT alias (exact). */ + ALIAS_MAY, /* The two refs MAY alias (inexact). */ + ALIAS_MUST /* The two refs MUST alias (exact). */ +} AliasRet; + +/* -- 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 = (IRRef)(ir - J->cur.ir); /* The ref 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 *taba = IR(ta), *tabb = IR(tb); + int newa, newb; + lj_assertJ(ta != tb, "bad usage"); + lj_assertJ(irt_istab(taba->t) && irt_istab(tabb->t), "bad usage"); + /* Disambiguate new allocations. */ + newa = (taba->o == IR_TNEW || taba->o == IR_TDUP); + newb = (tabb->o == IR_TNEW || tabb->o == IR_TDUP); + if (newa && newb) + return ALIAS_NO; /* Two different allocations never alias. */ + if (newb) { /* At least one allocation? */ + IRIns *tmp = taba; taba = tabb; tabb = tmp; + } else if (!newa) { + return ALIAS_MAY; /* Anything else: we just don't know. */ + } + return aa_escape(J, taba, tabb); +} + +/* Check whether there's no aliasing table.clear. */ +static int fwd_aa_tab_clear(jit_State *J, IRRef lim, IRRef ta) +{ + IRRef ref = J->chain[IR_CALLS]; + while (ref > lim) { + IRIns *calls = IR(ref); + if (calls->op2 == IRCALL_lj_tab_clear && + (ta == calls->op1 || aa_table(J, ta, calls->op1) != ALIAS_NO)) + return 0; /* Conflict. */ + ref = calls->prev; + } + return 1; /* No conflict. Can safely FOLD/CSE. */ +} + +/* Check whether there's no aliasing NEWREF/table.clear for the left operand. */ +int LJ_FASTCALL lj_opt_fwd_tptr(jit_State *J, IRRef lim) +{ + IRRef ta = fins->op1; + IRRef ref = J->chain[IR_NEWREF]; + while (ref > lim) { + IRIns *newref = IR(ref); + if (ta == newref->op1 || aa_table(J, ta, newref->op1) != ALIAS_NO) + return 0; /* Conflict. */ + ref = newref->prev; + } + return fwd_aa_tab_clear(J, lim, ta); +} + +/* Alias analysis for array and hash access using key-based disambiguation. */ +static AliasRet aa_ahref(jit_State *J, IRIns *refa, IRIns *refb) +{ + IRRef ka = refa->op2; + IRRef kb = refb->op2; + IRIns *keya, *keyb; + IRRef ta, tb; + if (refa == refb) + return ALIAS_MUST; /* Shortcut for same refs. */ + keya = IR(ka); + if (keya->o == IR_KSLOT) { ka = keya->op1; keya = IR(ka); } + keyb = IR(kb); + if (keyb->o == IR_KSLOT) { kb = keyb->op1; keyb = IR(kb); } + ta = (refa->o==IR_HREFK || refa->o==IR_AREF) ? IR(refa->op1)->op1 : refa->op1; + tb = (refb->o==IR_HREFK || refb->o==IR_AREF) ? IR(refb->op1)->op1 : refb->op1; + if (ka == kb) { + /* Same key. Check for same table with different ref (NEWREF vs. HREF). */ + if (ta == tb) + return ALIAS_MUST; /* Same key, same table. */ + else + return aa_table(J, ta, tb); /* Same key, possibly different table. */ + } + if (irref_isk(ka) && irref_isk(kb)) + return ALIAS_NO; /* Different constant keys. */ + if (refa->o == IR_AREF) { + /* Disambiguate array references based on index arithmetic. */ + int32_t ofsa = 0, ofsb = 0; + IRRef basea = ka, baseb = kb; + lj_assertJ(refb->o == IR_AREF, "expected AREF"); + /* Gather base and offset from t[base] or t[base+-ofs]. */ + if (keya->o == IR_ADD && irref_isk(keya->op2)) { + basea = keya->op1; + ofsa = IR(keya->op2)->i; + if (basea == kb && ofsa != 0) + return ALIAS_NO; /* t[base+-ofs] vs. t[base]. */ + } + if (keyb->o == IR_ADD && irref_isk(keyb->op2)) { + baseb = keyb->op1; + ofsb = IR(keyb->op2)->i; + if (ka == baseb && ofsb != 0) + return ALIAS_NO; /* t[base] vs. t[base+-ofs]. */ + } + if (basea == baseb && ofsa != ofsb) + return ALIAS_NO; /* t[base+-o1] vs. t[base+-o2] and o1 != o2. */ + } else { + /* Disambiguate hash references based on the type of their keys. */ + lj_assertJ((refa->o==IR_HREF || refa->o==IR_HREFK || refa->o==IR_NEWREF) && + (refb->o==IR_HREF || refb->o==IR_HREFK || refb->o==IR_NEWREF), + "bad xREF IR op %d or %d", refa->o, refb->o); + if (!irt_sametype(keya->t, keyb->t)) + return ALIAS_NO; /* Different key types. */ + } + if (ta == tb) + return ALIAS_MAY; /* Same table, cannot disambiguate keys. */ + else + return aa_table(J, ta, tb); /* Try to disambiguate tables. */ +} + +/* Array and hash load forwarding. */ +static TRef fwd_ahload(jit_State *J, IRRef xref) +{ + IRIns *xr = IR(xref); + IRRef lim = xref; /* Search limit. */ + IRRef ref; + + /* Search for conflicting stores. */ + ref = J->chain[fins->o+IRDELTA_L2S]; + while (ref > xref) { + IRIns *store = IR(ref); + switch (aa_ahref(J, xr, IR(store->op1))) { + 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. */ + } + ref = store->prev; + } + + /* No conflicting store (yet): const-fold loads from allocations. */ + { + IRIns *ir = (xr->o == IR_HREFK || xr->o == IR_AREF) ? IR(xr->op1) : xr; + IRRef tab = ir->op1; + ir = IR(tab); + if ((ir->o == IR_TNEW || (ir->o == IR_TDUP && irref_isk(xr->op2))) && + fwd_aa_tab_clear(J, tab, tab)) { + /* A NEWREF with a number key may end up pointing to the array part. + ** But it's referenced from HSTORE and not found in the ASTORE chain. + ** For now simply consider this a conflict without forwarding anything. + */ + if (xr->o == IR_AREF) { + IRRef ref2 = J->chain[IR_NEWREF]; + while (ref2 > tab) { + IRIns *newref = IR(ref2); + if (irt_isnum(IR(newref->op2)->t)) + goto cselim; + ref2 = newref->prev; + } + } + /* NEWREF inhibits CSE for HREF, and dependent FLOADs from HREFK/AREF. + ** But the above search for conflicting stores was limited by xref. + ** So continue searching, limited by the TNEW/TDUP. Store forwarding + ** is ok, too. A conflict does NOT limit the search for a matching load. + */ + while (ref > tab) { + IRIns *store = IR(ref); + switch (aa_ahref(J, xr, IR(store->op1))) { + case ALIAS_NO: break; /* Continue searching. */ + case ALIAS_MAY: goto cselim; /* Conflicting store. */ + case ALIAS_MUST: return store->op2; /* Store forwarding. */ + } + ref = store->prev; + } + if (ir->o == IR_TNEW && !irt_isnil(fins->t)) + return 0; /* Type instability in loop-carried dependency. */ + if (irt_ispri(fins->t)) { + return TREF_PRI(irt_type(fins->t)); + } else if (irt_isnum(fins->t) || (LJ_DUALNUM && irt_isint(fins->t)) || + irt_isstr(fins->t)) { + TValue keyv; + cTValue *tv; + IRIns *key = IR(xr->op2); + if (key->o == IR_KSLOT) key = IR(key->op1); + lj_ir_kvalue(J->L, &keyv, key); + tv = lj_tab_get(J->L, ir_ktab(IR(ir->op1)), &keyv); + lj_assertJ(itype2irt(tv) == irt_type(fins->t), + "mismatched type in constant table"); + if (irt_isnum(fins->t)) + return lj_ir_knum_u64(J, tv->u64); + else if (LJ_DUALNUM && irt_isint(fins->t)) + return lj_ir_kint(J, intV(tv)); + else + return lj_ir_kstr(J, strV(tv)); + } + /* Othwerwise: don't intern as a constant. */ + } + } + +cselim: + /* Try to find a matching load. Below the conflicting store, if any. */ + ref = J->chain[fins->o]; + while (ref > lim) { + IRIns *load = IR(ref); + if (load->op1 == xref) + return ref; /* Load forwarding. */ + ref = load->prev; + } + return 0; /* Conflict or no match. */ +} + +/* Reassociate ALOAD across PHIs to handle t[i-1] forwarding case. */ +static TRef fwd_aload_reassoc(jit_State *J) +{ + IRIns *irx = IR(fins->op1); + IRIns *key = IR(irx->op2); + if (key->o == IR_ADD && irref_isk(key->op2)) { + IRIns *add2 = IR(key->op1); + if (add2->o == IR_ADD && irref_isk(add2->op2) && + IR(key->op2)->i == -IR(add2->op2)->i) { + IRRef ref = J->chain[IR_AREF]; + IRRef lim = add2->op1; + if (irx->op1 > lim) lim = irx->op1; + while (ref > lim) { + IRIns *ir = IR(ref); + if (ir->op1 == irx->op1 && ir->op2 == add2->op1) + return fwd_ahload(J, ref); + ref = ir->prev; + } + } + } + return 0; +} + +/* ALOAD forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_aload(jit_State *J) +{ + IRRef ref; + if ((ref = fwd_ahload(J, fins->op1)) || + (ref = fwd_aload_reassoc(J))) + return ref; + return EMITFOLD; +} + +/* HLOAD forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_hload(jit_State *J) +{ + IRRef ref = fwd_ahload(J, fins->op1); + if (ref) + return ref; + return EMITFOLD; +} + +/* HREFK forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_hrefk(jit_State *J) +{ + IRRef tab = fleft->op1; + IRRef ref = J->chain[IR_NEWREF]; + while (ref > tab) { + IRIns *newref = IR(ref); + if (tab == newref->op1) { + if (fright->op1 == newref->op2 && fwd_aa_tab_clear(J, ref, tab)) + return ref; /* Forward from NEWREF. */ + else + goto docse; + } else if (aa_table(J, tab, newref->op1) != ALIAS_NO) { + goto docse; + } + ref = newref->prev; + } + /* No conflicting NEWREF: key location unchanged for HREFK of TDUP. */ + if (IR(tab)->o == IR_TDUP && fwd_aa_tab_clear(J, tab, tab)) + fins->t.irt &= ~IRT_GUARD; /* Drop HREFK guard. */ +docse: + return CSEFOLD; +} + +/* Check whether HREF of TNEW/TDUP can be folded to niltv. */ +int LJ_FASTCALL lj_opt_fwd_href_nokey(jit_State *J) +{ + IRRef lim = fins->op1; /* Search limit. */ + IRRef ref; + + /* The key for an ASTORE may end up in the hash part after a NEWREF. */ + if (irt_isnum(fright->t) && J->chain[IR_NEWREF] > lim) { + ref = J->chain[IR_ASTORE]; + while (ref > lim) { + if (ref < J->chain[IR_NEWREF]) + return 0; /* Conflict. */ + ref = IR(ref)->prev; + } + } + + /* Search for conflicting stores. */ + ref = J->chain[IR_HSTORE]; + while (ref > lim) { + IRIns *store = IR(ref); + if (aa_ahref(J, fins, IR(store->op1)) != ALIAS_NO) + return 0; /* Conflict. */ + ref = store->prev; + } + + return 1; /* No conflict. Can fold to niltv. */ +} + +/* ASTORE/HSTORE elimination. */ +TRef LJ_FASTCALL lj_opt_dse_ahstore(jit_State *J) +{ + IRRef xref = fins->op1; /* xREF reference. */ + IRRef val = fins->op2; /* Stored value reference. */ + IRIns *xr = IR(xref); + IRRef1 *refp = &J->chain[fins->o]; + IRRef ref = *refp; + while (ref > xref) { /* Search for redundant or conflicting stores. */ + IRIns *store = IR(ref); + switch (aa_ahref(J, xr, IR(store->op1))) { + case ALIAS_NO: + break; /* Continue searching. */ + case ALIAS_MAY: /* Store to MAYBE the same location. */ + if (store->op2 != val) /* Conflict if the value is different. */ + goto doemit; + break; /* Otherwise continue searching. */ + case ALIAS_MUST: /* Store to the same location. */ + if (store->op2 == val) /* Same value: drop the new store. */ + return DROPFOLD; + /* Different value: try to eliminate the redundant store. */ + if (ref > J->chain[IR_LOOP]) { /* Quick check to avoid crossing LOOP. */ + IRIns *ir; + /* Check for any intervening guards (includes conflicting loads). + ** Note that lj_tab_keyindex and lj_vm_next don't need guards, + ** since they are followed by at least one guarded VLOAD. + */ + for (ir = IR(J->cur.nins-1); ir > store; ir--) + if (irt_isguard(ir->t) || ir->o == IR_ALEN) + goto doemit; /* No elimination possible. */ + /* Remove redundant store from chain and replace with NOP. */ + *refp = store->prev; + lj_ir_nop(store); + /* Now emit the new store instead. */ + } + goto doemit; + } + ref = *(refp = &store->prev); + } +doemit: + return EMITFOLD; /* Otherwise we have a conflict or simply no match. */ +} + +/* ALEN forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_alen(jit_State *J) +{ + IRRef tab = fins->op1; /* Table reference. */ + IRRef lim = tab; /* Search limit. */ + IRRef ref; + + /* Search for conflicting HSTORE with numeric key. */ + ref = J->chain[IR_HSTORE]; + while (ref > lim) { + IRIns *store = IR(ref); + IRIns *href = IR(store->op1); + IRIns *key = IR(href->op2); + if (irt_isnum(key->o == IR_KSLOT ? IR(key->op1)->t : key->t)) { + lim = ref; /* Conflicting store found, limits search for ALEN. */ + break; + } + ref = store->prev; + } + + /* Try to find a matching ALEN. */ + ref = J->chain[IR_ALEN]; + while (ref > lim) { + /* CSE for ALEN only depends on the table, not the hint. */ + if (IR(ref)->op1 == tab) { + IRRef sref; + + /* Search for aliasing table.clear. */ + if (!fwd_aa_tab_clear(J, ref, tab)) + break; + + /* Search for hint-forwarding or conflicting store. */ + sref = J->chain[IR_ASTORE]; + while (sref > ref) { + IRIns *store = IR(sref); + IRIns *aref = IR(store->op1); + IRIns *fref = IR(aref->op1); + if (tab == fref->op1) { /* ASTORE to the same table. */ + /* Detect t[#t+1] = x idiom for push. */ + IRIns *idx = IR(aref->op2); + if (!irt_isnil(store->t) && + idx->o == IR_ADD && idx->op1 == ref && + IR(idx->op2)->o == IR_KINT && IR(idx->op2)->i == 1) { + /* Note: this requires an extra PHI check in loop unroll. */ + fins->op2 = aref->op2; /* Set ALEN hint. */ + } + goto doemit; /* Conflicting store, possibly giving a hint. */ + } else if (aa_table(J, tab, fref->op1) != ALIAS_NO) { + goto doemit; /* Conflicting store. */ + } + sref = store->prev; + } + + return ref; /* Plain ALEN forwarding. */ + } + ref = IR(ref)->prev; + } +doemit: + return EMITFOLD; +} + +/* -- ULOAD forwarding ---------------------------------------------------- */ + +/* The current alias analysis for upvalues is very simplistic. It only +** disambiguates between the unique upvalues of the same function. +** This is good enough for now, since most upvalues are read-only. +** +** A more precise analysis would be feasible with the help of the parser: +** generate a unique key for every upvalue, even across all prototypes. +** Lacking a realistic use-case, it's unclear whether this is beneficial. +*/ +static AliasRet aa_uref(IRIns *refa, IRIns *refb) +{ + if (refa->o != refb->o) + return ALIAS_NO; /* Different UREFx type. */ + if (refa->op1 == refb->op1) { /* Same function. */ + if (refa->op2 == refb->op2) + return ALIAS_MUST; /* Same function, same upvalue idx. */ + else + return ALIAS_NO; /* Same function, different upvalue idx. */ + } else { /* Different functions, check disambiguation hash values. */ + if (((refa->op2 ^ refb->op2) & 0xff)) + return ALIAS_NO; /* Upvalues with different hash values cannot alias. */ + else + return ALIAS_MAY; /* No conclusion can be drawn for same hash value. */ + } +} + +/* ULOAD forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_uload(jit_State *J) +{ + IRRef uref = fins->op1; + IRRef lim = REF_BASE; /* Search limit. */ + IRIns *xr = IR(uref); + IRRef ref; + + /* Search for conflicting stores. */ + ref = J->chain[IR_USTORE]; + while (ref > lim) { + IRIns *store = IR(ref); + switch (aa_uref(xr, IR(store->op1))) { + 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. */ + } + ref = store->prev; + } + +cselim: + /* Try to find a matching load. Below the conflicting store, if any. */ + ref = J->chain[IR_ULOAD]; + while (ref > lim) { + IRIns *ir = IR(ref); + if (ir->op1 == uref || + (IR(ir->op1)->op12 == IR(uref)->op12 && IR(ir->op1)->o == IR(uref)->o)) + return ref; /* Match for identical or equal UREFx (non-CSEable UREFO). */ + ref = ir->prev; + } + return lj_ir_emit(J); +} + +/* USTORE elimination. */ +TRef LJ_FASTCALL lj_opt_dse_ustore(jit_State *J) +{ + IRRef xref = fins->op1; /* xREF reference. */ + IRRef val = fins->op2; /* Stored value reference. */ + IRIns *xr = IR(xref); + IRRef1 *refp = &J->chain[IR_USTORE]; + IRRef ref = *refp; + while (ref > xref) { /* Search for redundant or conflicting stores. */ + IRIns *store = IR(ref); + switch (aa_uref(xr, IR(store->op1))) { + case ALIAS_NO: + break; /* Continue searching. */ + case ALIAS_MAY: /* Store to MAYBE the same location. */ + if (store->op2 != val) /* Conflict if the value is different. */ + goto doemit; + break; /* Otherwise continue searching. */ + case ALIAS_MUST: /* Store to the same location. */ + if (store->op2 == val) /* Same value: drop the new store. */ + return DROPFOLD; + /* Different value: try to eliminate the redundant store. */ + if (ref > J->chain[IR_LOOP]) { /* Quick check to avoid crossing LOOP. */ + IRIns *ir; + /* Check for any intervening guards (includes conflicting loads). */ + for (ir = IR(J->cur.nins-1); ir > store; ir--) + if (irt_isguard(ir->t)) + goto doemit; /* No elimination possible. */ + /* Remove redundant store from chain and replace with NOP. */ + *refp = store->prev; + lj_ir_nop(store); + if (ref+1 < J->cur.nins && + store[1].o == IR_OBAR && store[1].op1 == xref) { + IRRef1 *bp = &J->chain[IR_OBAR]; + IRIns *obar; + for (obar = IR(*bp); *bp > ref+1; obar = IR(*bp)) + bp = &obar->prev; + /* Remove OBAR, too. */ + *bp = obar->prev; + lj_ir_nop(obar); + } + /* Now emit the new store instead. */ + } + goto doemit; + } + ref = *(refp = &store->prev); + } +doemit: + return EMITFOLD; /* Otherwise we have a conflict or simply no match. */ +} + +/* -- FLOAD forwarding and FSTORE elimination ----------------------------- */ + +/* Alias analysis for field access. +** Field loads are cheap and field stores are rare. +** Simple disambiguation based on field types is good enough. +*/ +static AliasRet aa_fref(jit_State *J, IRIns *refa, IRIns *refb) +{ + if (refa->op2 != refb->op2) + return ALIAS_NO; /* Different fields. */ + if (refa->op1 == refb->op1) + return ALIAS_MUST; /* Same field, same object. */ + else if (refa->op2 >= IRFL_TAB_META && refa->op2 <= IRFL_TAB_NOMM) + return aa_table(J, refa->op1, refb->op1); /* Disambiguate tables. */ + else + return ALIAS_MAY; /* Same field, possibly different object. */ +} + +/* Only the loads for mutable fields end up here (see FOLD). */ +TRef LJ_FASTCALL lj_opt_fwd_fload(jit_State *J) +{ + IRRef oref = fins->op1; /* Object reference. */ + IRRef fid = fins->op2; /* Field ID. */ + IRRef lim = oref; /* Search limit. */ + IRRef ref; + + /* Search for conflicting stores. */ + ref = J->chain[IR_FSTORE]; + while (ref > oref) { + IRIns *store = IR(ref); + switch (aa_fref(J, fins, IR(store->op1))) { + 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. */ + } + ref = store->prev; + } + + /* No conflicting store: const-fold field loads from allocations. */ + if (fid == IRFL_TAB_META) { + IRIns *ir = IR(oref); + if (ir->o == IR_TNEW || ir->o == IR_TDUP) + return lj_ir_knull(J, IRT_TAB); + } + +cselim: + /* Try to find a matching load. Below the conflicting store, if any. */ + return lj_opt_cselim(J, lim); +} + +/* FSTORE elimination. */ +TRef LJ_FASTCALL lj_opt_dse_fstore(jit_State *J) +{ + IRRef fref = fins->op1; /* FREF reference. */ + IRRef val = fins->op2; /* Stored value reference. */ + IRIns *xr = IR(fref); + IRRef1 *refp = &J->chain[IR_FSTORE]; + IRRef ref = *refp; + while (ref > fref) { /* Search for redundant or conflicting stores. */ + IRIns *store = IR(ref); + switch (aa_fref(J, xr, IR(store->op1))) { + case ALIAS_NO: + break; /* Continue searching. */ + case ALIAS_MAY: + if (store->op2 != val) /* Conflict if the value is different. */ + goto doemit; + break; /* Otherwise continue searching. */ + case ALIAS_MUST: + if (store->op2 == val && + !(xr->op2 >= IRFL_SBUF_W && xr->op2 <= IRFL_SBUF_R)) + return DROPFOLD; /* Same value: drop the new store. */ + /* Different value: try to eliminate the redundant store. */ + if (ref > J->chain[IR_LOOP]) { /* Quick check to avoid crossing LOOP. */ + IRIns *ir; + /* Check for any intervening guards or conflicting loads. */ + for (ir = IR(J->cur.nins-1); ir > store; ir--) + if (irt_isguard(ir->t) || (ir->o == IR_FLOAD && ir->op2 == xr->op2)) + goto doemit; /* No elimination possible. */ + /* Remove redundant store from chain and replace with NOP. */ + *refp = store->prev; + lj_ir_nop(store); + /* Now emit the new store instead. */ + } + goto doemit; + } + ref = *(refp = &store->prev); + } +doemit: + return EMITFOLD; /* Otherwise we have a conflict or simply no match. */ +} + +/* Check whether there's no aliasing buffer op between IRFL_SBUF_*. */ +int LJ_FASTCALL lj_opt_fwd_sbuf(jit_State *J, IRRef lim) +{ + IRRef ref; + if (J->chain[IR_BUFPUT] > lim) + return 0; /* Conflict. */ + ref = J->chain[IR_CALLS]; + while (ref > lim) { + IRIns *ir = IR(ref); + if (ir->op2 >= IRCALL_lj_strfmt_putint && ir->op2 < IRCALL_lj_buf_tostr) + return 0; /* Conflict. */ + ref = ir->prev; + } + ref = J->chain[IR_CALLL]; + while (ref > lim) { + IRIns *ir = IR(ref); + if (ir->op2 >= IRCALL_lj_strfmt_putint && ir->op2 < IRCALL_lj_buf_tostr) + return 0; /* Conflict. */ + ref = ir->prev; + } + return 1; /* No conflict. Can safely FOLD/CSE. */ +} + +/* -- 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 *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. */ +} + +/* Return CSEd reference or 0. Caveat: swaps lower ref to the right! */ +static IRRef reassoc_trycse(jit_State *J, IROp op, IRRef op1, IRRef op2) +{ + IRRef ref = J->chain[op]; + IRRef lim = op1; + if (op2 > lim) { lim = op2; op2 = op1; op1 = lim; } + while (ref > lim) { + IRIns *ir = IR(ref); + if (ir->op1 == op1 && ir->op2 == op2) + return ref; + ref = ir->prev; + } + return 0; +} + +/* Reassociate index references. */ +static IRRef reassoc_xref(jit_State *J, IRIns *ir) +{ + ptrdiff_t ofs = 0; + if (ir->o == IR_ADD && irref_isk(ir->op2)) { /* Get constant offset. */ + IRIns *irk = IR(ir->op2); + ofs = (LJ_64 && irk->o == IR_KINT64) ? (ptrdiff_t)ir_k64(irk)->u64 : + (ptrdiff_t)irk->i; + ir = IR(ir->op1); + } + if (ir->o == IR_ADD) { /* Add of base + index. */ + /* Index ref > base ref for loop-carried dependences. Only check op1. */ + IRIns *ir2, *ir1 = IR(ir->op1); + int32_t shift = 0; + IRRef idxref; + /* Determine index shifts. Don't bother with IR_MUL here. */ + if (ir1->o == IR_BSHL && irref_isk(ir1->op2)) + shift = IR(ir1->op2)->i; + else if (ir1->o == IR_ADD && ir1->op1 == ir1->op2) + shift = 1; + else + ir1 = ir; + ir2 = IR(ir1->op1); + /* A non-reassociated add. Must be a loop-carried dependence. */ + if (ir2->o == IR_ADD && irt_isint(ir2->t) && irref_isk(ir2->op2)) + ofs += (ptrdiff_t)IR(ir2->op2)->i << shift; + else + return 0; + idxref = ir2->op1; + /* Try to CSE the reassociated chain. Give up if not found. */ + if (ir1 != ir && + !(idxref = reassoc_trycse(J, ir1->o, idxref, + ir1->o == IR_BSHL ? ir1->op2 : idxref))) + return 0; + if (!(idxref = reassoc_trycse(J, IR_ADD, idxref, ir->op2))) + return 0; + if (ofs != 0) { + IRRef refk = tref_ref(lj_ir_kintp(J, ofs)); + if (!(idxref = reassoc_trycse(J, IR_ADD, idxref, refk))) + return 0; + } + return idxref; /* Success, found a reassociated index reference. Phew. */ + } + return 0; /* Failure. */ +} + +/* XLOAD forwarding. */ +TRef LJ_FASTCALL lj_opt_fwd_xload(jit_State *J) +{ + IRRef xref = fins->op1; + IRIns *xr = IR(xref); + IRRef lim = xref; /* Search limit. */ + IRRef ref; + + if ((fins->op2 & IRXLOAD_READONLY)) + goto cselim; + if ((fins->op2 & IRXLOAD_VOLATILE)) + goto doemit; + + /* Search for conflicting stores. */ + ref = J->chain[IR_XSTORE]; +retry: + if (J->chain[IR_CALLXS] > lim) lim = J->chain[IR_CALLXS]; + if (J->chain[IR_XBAR] > lim) lim = J->chain[IR_XBAR]; + while (ref > lim) { + IRIns *store = IR(ref); + switch (aa_xref(J, xr, fins, store)) { + case ALIAS_NO: break; /* Continue searching. */ + case ALIAS_MAY: lim = ref; goto cselim; /* Limit search for load. */ + case ALIAS_MUST: + /* Emit conversion if the loaded type doesn't match the forwarded type. */ + if (!irt_sametype(fins->t, IR(store->op2)->t)) { + IRType dt = irt_type(fins->t), st = irt_type(IR(store->op2)->t); + if (dt == IRT_I8 || dt == IRT_I16) { /* Trunc + sign-extend. */ + st = dt | IRCONV_SEXT; + dt = IRT_INT; + } else if (dt == IRT_U8 || dt == IRT_U16) { /* Trunc + zero-extend. */ + st = dt; + dt = IRT_INT; + } + fins->ot = IRT(IR_CONV, dt); + fins->op1 = store->op2; + fins->op2 = (dt<<5)|st; + return RETRYFOLD; + } + return store->op2; /* Store forwarding. */ + } + ref = store->prev; + } + +cselim: + /* Try to find a matching load. Below the conflicting store, if any. */ + ref = J->chain[IR_XLOAD]; + while (ref > lim) { + /* CSE for XLOAD depends on the type, but not on the IRXLOAD_* flags. */ + if (IR(ref)->op1 == xref && irt_sametype(IR(ref)->t, fins->t)) + return ref; + ref = IR(ref)->prev; + } + + /* Reassociate XLOAD across PHIs to handle a[i-1] forwarding case. */ + if (!(fins->op2 & IRXLOAD_READONLY) && J->chain[IR_LOOP] && + xref == fins->op1 && (xref = reassoc_xref(J, xr)) != 0) { + ref = J->chain[IR_XSTORE]; + while (ref > lim) /* Skip stores that have already been checked. */ + ref = IR(ref)->prev; + lim = xref; + xr = IR(xref); + goto retry; /* Retry with the reassociated reference. */ + } +doemit: + return EMITFOLD; +} + +/* XSTORE elimination. */ +TRef LJ_FASTCALL lj_opt_dse_xstore(jit_State *J) +{ + IRRef xref = fins->op1; + IRIns *xr = IR(xref); + IRRef lim = xref; /* Search limit. */ + IRRef val = fins->op2; /* Stored value reference. */ + IRRef1 *refp = &J->chain[IR_XSTORE]; + IRRef ref = *refp; + if (J->chain[IR_CALLXS] > lim) lim = J->chain[IR_CALLXS]; + if (J->chain[IR_XBAR] > lim) lim = J->chain[IR_XBAR]; + if (J->chain[IR_XSNEW] > lim) lim = J->chain[IR_XSNEW]; + while (ref > lim) { /* Search for redundant or conflicting stores. */ + IRIns *store = IR(ref); + switch (aa_xref(J, xr, fins, store)) { + case ALIAS_NO: + break; /* Continue searching. */ + case ALIAS_MAY: + if (store->op2 != val) /* Conflict if the value is different. */ + goto doemit; + break; /* Otherwise continue searching. */ + case ALIAS_MUST: + if (store->op2 == val) /* Same value: drop the new store. */ + return DROPFOLD; + /* Different value: try to eliminate the redundant store. */ + if (ref > J->chain[IR_LOOP]) { /* Quick check to avoid crossing LOOP. */ + IRIns *ir; + /* Check for any intervening guards or any XLOADs (no AA performed). */ + for (ir = IR(J->cur.nins-1); ir > store; ir--) + if (irt_isguard(ir->t) || ir->o == IR_XLOAD) + goto doemit; /* No elimination possible. */ + /* Remove redundant store from chain and replace with NOP. */ + *refp = store->prev; + lj_ir_nop(store); + /* Now emit the new store instead. */ + } + goto doemit; + } + ref = *(refp = &store->prev); + } +doemit: + return EMITFOLD; /* Otherwise we have a conflict or simply no match. */ +} + +/* -- ASTORE/HSTORE previous type analysis -------------------------------- */ + +/* Check whether the previous value for a table store is non-nil. +** This can be derived either from a previous store or from a previous +** load (because all loads from tables perform a type check). +** +** The result of the analysis can be used to avoid the metatable check +** and the guard against HREF returning niltv. Both of these are cheap, +** so let's not spend too much effort on the analysis. +** +** A result of 1 is exact: previous value CANNOT be nil. +** A result of 0 is inexact: previous value MAY be nil. +*/ +int lj_opt_fwd_wasnonnil(jit_State *J, IROpT loadop, IRRef xref) +{ + /* First check stores. */ + IRRef ref = J->chain[loadop+IRDELTA_L2S]; + while (ref > xref) { + IRIns *store = IR(ref); + if (store->op1 == xref) { /* Same xREF. */ + /* A nil store MAY alias, but a non-nil store MUST alias. */ + return !irt_isnil(store->t); + } else if (irt_isnil(store->t)) { /* Must check any nil store. */ + IRRef skref = IR(store->op1)->op2; + IRRef xkref = IR(xref)->op2; + /* Same key type MAY alias. Need ALOAD check due to multiple int types. */ + if (loadop == IR_ALOAD || irt_sametype(IR(skref)->t, IR(xkref)->t)) { + if (skref == xkref || !irref_isk(skref) || !irref_isk(xkref)) + return 0; /* A nil store with same const key or var key MAY alias. */ + /* Different const keys CANNOT alias. */ + } /* Different key types CANNOT alias. */ + } /* Other non-nil stores MAY alias. */ + ref = store->prev; + } + + /* Check loads since nothing could be derived from stores. */ + ref = J->chain[loadop]; + while (ref > xref) { + IRIns *load = IR(ref); + if (load->op1 == xref) { /* Same xREF. */ + /* A nil load MAY alias, but a non-nil load MUST alias. */ + return !irt_isnil(load->t); + } /* Other non-nil loads MAY alias. */ + ref = load->prev; + } + return 0; /* Nothing derived at all, previous value MAY be nil. */ +} + +/* ------------------------------------------------------------------------ */ + +#undef IR +#undef fins +#undef fleft +#undef fright + +#endif |