gh-mirror/mikepaul-LuaJIT
1
0
Fork 0
mirror of https://github.com/LuaJIT/LuaJIT.git synced 2025-02-07 23:24:09 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Make the IR immovable after assembly.

Browse Source 
This allows embedding pointers to IR constants in the machine code.
Contributed by Peter Cawley.
This commit is contained in:
Mike Pall 2016-05-22 23:25:28 +02:00
parent 513587656a
commit a657fa0186
4 changed files with 97 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

69
src/lj_asm.c
View File

@ -625,9 +625,8 @@ static void ra_addrename(ASMState *as, Reg down, IRRef ref, SnapNo snapno)
IRRef ren;
lj_ir_set(as->J, IRT(IR_RENAME, IRT_NIL), ref, snapno);
ren = tref_ref(lj_ir_emit(as->J));
as->ir = as->T->ir; /* The IR may have been reallocated. */
IR(ren)->r = (uint8_t)down;
IR(ren)->s = SPS_NONE;
as->J->cur.ir[ren].r = (uint8_t)down;
as->J->cur.ir[ren].s = SPS_NONE;
}
/* Rename register allocation and emit move. */
@ -948,7 +947,7 @@ static void asm_snap_prep(ASMState *as)
} else {
/* Process any renames above the highwater mark. */
for (; as->snaprename < as->T->nins; as->snaprename++) {
IRIns *ir = IR(as->snaprename);
IRIns *ir = &as->T->ir[as->snaprename];
if (asm_snap_checkrename(as, ir->op1))
ir->op2 = REF_BIAS-1; /* Kill rename. */
}
@ -1967,8 +1966,9 @@ static void asm_setup_regsp(ASMState *as)
ir = IR(nins-1);
if (ir->o == IR_RENAME) {
/* Remove any renames left over from ASM restart due to LJ_TRERR_MCODELM. */
do { ir--; nins--; } while (ir->o == IR_RENAME);
T->nins = nins; /* Remove any renames left over from ASM restart. */
T->nins = nins;
}
as->snaprename = nins;
as->snapref = nins;
@ -2202,13 +2202,14 @@ void lj_asm_trace(jit_State *J, GCtrace *T)
MCode *origtop;
/* Ensure an initialized instruction beyond the last one for HIOP checks. */
J->cur.nins = lj_ir_nextins(J);
J->cur.ir[J->cur.nins].o = IR_NOP;
/* This also allows one RENAME to be added without reallocating curfinal. */
as->orignins = lj_ir_nextins(J);
J->cur.ir[as->orignins].o = IR_NOP;
/* Setup initial state. Copy some fields to reduce indirections. */
as->J = J;
as->T = T;
as->ir = T->ir;
J->curfinal = lj_trace_alloc(J->L, T); /* This copies the IR, too. */
as->flags = J->flags;
as->loopref = J->loopref;
as->realign = NULL;
@ -2221,12 +2222,41 @@ void lj_asm_trace(jit_State *J, GCtrace *T)
as->mclim = as->mcbot + MCLIM_REDZONE;
asm_setup_target(as);
do {
/*
** This is a loop, because the MCode may have to be (re-)assembled
** multiple times:
**
** 1. as->realign is set (and the assembly aborted), if the arch-specific
** backend wants the MCode to be aligned differently.
**
** This is currently only the case on x86/x64, where small loops get
** an aligned loop body plus a short branch. Not much effort is wasted,
** because the abort happens very quickly and only once.
**
** 2. The IR is immovable, since the MCode embeds pointers to various
** constants inside the IR. But RENAMEs may need to be added to the IR
** during assembly, which might grow and reallocate the IR. We check
** at the end if the IR (in J->cur.ir) has actually grown, resize the
** copy (in J->curfinal.ir) and try again.
**
** 95% of all traces have zero RENAMEs, 3% have one RENAME, 1.5% have
** 2 RENAMEs and only 0.5% have more than that. That's why we opt to
** always have one spare slot in the IR (see above), which means we
** have to redo the assembly for only ~2% of all traces.
**
** Very, very rarely, this needs to be done repeatedly, since the
** location of constants inside the IR (actually, reachability from
** a global pointer) may affect register allocation and thus the
** number of RENAMEs.
*/
for (;;) {
as->mcp = as->mctop;
#ifdef LUA_USE_ASSERT
as->mcp_prev = as->mcp;
#endif
as->curins = T->nins;
as->ir = J->curfinal->ir; /* Use the copied IR. */
as->curins = J->cur.nins = as->orignins;
RA_DBG_START();
RA_DBGX((as, "===== STOP ====="));
@ -2254,7 +2284,9 @@ void lj_asm_trace(jit_State *J, GCtrace *T)
checkmclim(as);
asm_ir(as, ir);
}
} while (as->realign); /* Retry in case the MCode needs to be realigned. */
if (as->realign && J->curfinal->nins >= T->nins)
continue; /* Retry in case only the MCode needs to be realigned. */
/* Emit head of trace. */
RA_DBG_REF();
@ -2271,6 +2303,21 @@ void lj_asm_trace(jit_State *J, GCtrace *T)
asm_head_root(as);
asm_phi_fixup(as);
if (J->curfinal->nins >= T->nins) { /* IR didn't grow? */
lua_assert(J->curfinal->nk == T->nk);
memcpy(J->curfinal->ir + as->orignins, T->ir + as->orignins,
(T->nins - as->orignins) * sizeof(IRIns)); /* Copy RENAMEs. */
T->nins = J->curfinal->nins;
break; /* Done. */
}
/* Otherwise try again with a bigger IR. */
lj_trace_free(J2G(J), J->curfinal);
J->curfinal = NULL; /* In case lj_trace_alloc() OOMs. */
J->curfinal = lj_trace_alloc(J->L, T);
as->realign = NULL;
}
RA_DBGX((as, "===== START ===="));
RA_DBG_FLUSH();
if (as->freeset != RSET_ALL)

1
src/lj_jit.h
View File

@ -362,6 +362,7 @@ typedef struct FoldState {
/* JIT compiler state. */
typedef struct jit_State {
GCtrace cur; /* Current trace. */
GCtrace *curfinal; /* Final address of current trace (set during asm). */
lua_State *L; /* Current Lua state. */
const BCIns *pc; /* Current PC. */

33
src/lj_trace.c
View File

@ -117,15 +117,26 @@ static void perftools_addtrace(GCtrace *T)
}
#endif
/* Allocate space for copy of trace. */
static GCtrace *trace_save_alloc(jit_State *J)
/* Allocate space for copy of T. */
GCtrace * LJ_FASTCALL lj_trace_alloc(lua_State *L, GCtrace *T)
{
size_t sztr = ((sizeof(GCtrace)+7)&~7);
size_t szins = (J->cur.nins-J->cur.nk)*sizeof(IRIns);
size_t szins = (T->nins-T->nk)*sizeof(IRIns);
size_t sz = sztr + szins +
J->cur.nsnap*sizeof(SnapShot) +
J->cur.nsnapmap*sizeof(SnapEntry);
return lj_mem_newt(J->L, (MSize)sz, GCtrace);
T->nsnap*sizeof(SnapShot) +
T->nsnapmap*sizeof(SnapEntry);
GCtrace *T2 = lj_mem_newt(L, (MSize)sz, GCtrace);
char *p = (char *)T2 + sztr;
T2->gct = ~LJ_TTRACE;
T2->marked = 0;
T2->traceno = 0;
T2->ir = (IRIns *)p - T->nk;
T2->nins = T->nins;
T2->nk = T->nk;
T2->nsnap = T->nsnap;
T2->nsnapmap = T->nsnapmap;
memcpy(p, T->ir + T->nk, szins);
return T2;
}
/* Save current trace by copying and compacting it. */
@ -139,12 +150,12 @@ static void trace_save(jit_State *J, GCtrace *T)
setgcrefp(J2G(J)->gc.root, T);
newwhite(J2G(J), T);
T->gct = ~LJ_TTRACE;
T->ir = (IRIns *)p - J->cur.nk;
memcpy(p, J->cur.ir+J->cur.nk, szins);
T->ir = (IRIns *)p - J->cur.nk; /* The IR has already been copied above. */
p += szins;
TRACE_APPENDVEC(snap, nsnap, SnapShot)
TRACE_APPENDVEC(snapmap, nsnapmap, SnapEntry)
J->cur.traceno = 0;
J->curfinal = NULL;
setgcrefp(J->trace[T->traceno], T);
lj_gc_barriertrace(J2G(J), T->traceno);
lj_gdbjit_addtrace(J, T);
@ -449,7 +460,7 @@ static void trace_stop(jit_State *J)
BCOp op = bc_op(J->cur.startins);
GCproto *pt = &gcref(J->cur.startpt)->pt;
TraceNo traceno = J->cur.traceno;
GCtrace *T = trace_save_alloc(J); /* Do this first. May throw OOM. */
GCtrace *T = J->curfinal;
lua_State *L;
switch (op) {
@ -537,6 +548,10 @@ static int trace_abort(jit_State *J)
J->postproc = LJ_POST_NONE;
lj_mcode_abort(J);
if (J->curfinal) {
lj_trace_free(J2G(J), J->curfinal);
J->curfinal = NULL;
}
if (tvisnumber(L->top-1))
e = (TraceError)numberVint(L->top-1);
if (e == LJ_TRERR_MCODELM) {

1
src/lj_trace.h
View File

@ -23,6 +23,7 @@ LJ_FUNC_NORET void lj_trace_err(jit_State *J, TraceError e);
LJ_FUNC_NORET void lj_trace_err_info(jit_State *J, TraceError e);
/* Trace management. */
LJ_FUNC GCtrace * LJ_FASTCALL lj_trace_alloc(lua_State *L, GCtrace *T);
LJ_FUNC void LJ_FASTCALL lj_trace_free(global_State *g, GCtrace *T);
LJ_FUNC void lj_trace_reenableproto(GCproto *pt);
LJ_FUNC void lj_trace_flushproto(global_State *g, GCproto *pt);