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deopt.c
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deopt.c
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#include "moar.h"
/* In some cases, we may have specialized bytecode "on the stack" and need to
* back out of it, because some assumption it made has been invalidated. This
* file contains implementations of those various forms of de-opt. */
#define MVM_LOG_DEOPTS 0
/* Uninlining can invalidate what the dynlex cache points to, so we'll
* clear it in various caches. */
MVM_STATIC_INLINE void clear_dynlex_cache(MVMThreadContext *tc, MVMFrame *f) {
MVMFrameExtra *e = f->extra;
if (e) {
e->dynlex_cache_name = NULL;
e->dynlex_cache_reg = NULL;
}
}
/* If we have to deopt inside of a frame containing inlines, and we're in
* an inlined frame at the point we hit deopt, we need to undo the inlining
* by switching all levels of inlined frame out for a bunch of frames that
* are running the de-optimized code. We may, of course, be in the original,
* non-inline, bit of the code - in which case we've nothing to do once we
* have determined that.
*
* We can rely on the frame we are doing uninling on always being the top
* record on the callstack.
*/
static void uninline(MVMThreadContext *tc, MVMFrame *f, MVMSpeshCandidate *cand,
MVMuint32 offset, MVMint32 all, MVMint32 is_pre) {
/* Make absolutely sure this is the top thing on the callstack. */
assert(MVM_callstack_current_frame(tc) == f);
/* We know that nothing can reference an inlined frame (trivially - it did
* not exist to reference!) Thus it can be created on the stack. We need to
* recreate the frames deepest first. The inlines list is sorted most nested
* first, thus we traverse it in the opposite order. */
MVMint32 i;
for (i = cand->body.num_inlines - 1; i >= 0; i--) {
MVMuint32 start = cand->body.inlines[i].start;
MVMuint32 end = cand->body.inlines[i].end;
if ((is_pre ? offset >= start : offset > start) &&
(all || !is_pre ? offset <= end : offset < end)) {
/* Grab the current frame, which is the caller of this inline. */
MVMFrame *caller = MVM_callstack_current_frame(tc);
/* Does the inline have any dispatch resume arg initializations?
* If so, we'll need to recreate a dispatch run record under the
* call frame, in order that we can successfully resume. */
if (cand->body.inlines[i].first_spesh_resume_init != -1) {
MVMint32 j = cand->body.inlines[i].last_spesh_resume_init;
while (j >= cand->body.inlines[i].first_spesh_resume_init) {
/* Allocate the resume init record. */
MVMSpeshResumeInit *ri = &(cand->body.resume_inits[j]);
MVMCallStackDeoptedResumeInit *dri =
MVM_callstack_allocate_deopted_resume_init(tc, ri);
/* Evacuate the current dispatch state. */
dri->state = f->work[ri->state_register].o;
/* Evacuate all non-constant resume init args. */
if (dri->dpr->init_values) {
/* Complex init values; make sure only to copy args
* and temporaries. */
MVMuint16 k;
for (k = 0; k < dri->dpr->init_callsite->flag_count; k++) {
switch (dri->dpr->init_values[k].source) {
case MVM_DISP_RESUME_INIT_ARG:
case MVM_DISP_RESUME_INIT_TEMP:
dri->args[k] = f->work[ri->init_registers[k]];
break;
default:
/* Constant, ignore. */
break;
}
}
}
else {
/* Just the plain args, so we find them linearly in. */
MVMuint16 k;
for (k = 0; k < dri->dpr->init_callsite->flag_count; k++)
dri->args[k] = f->work[ri->init_registers[k]];
}
j--;
}
}
/* Resolve the inline's code object and static frame. */
MVMStaticFrame *usf = cand->body.inlines[i].sf;
MVMCode *ucode = (MVMCode *)f->work[cand->body.inlines[i].code_ref_reg].o;
if (REPR(ucode)->ID != MVM_REPR_ID_MVMCode)
MVM_panic(1, "Deopt: did not find code object when uninlining");
/* Make a record for it on the stack; the MVMFrame is contained in
* it. Set up the frame. Note that this moves tc->stack_top, so we
* are now considered to be in this frame. */
MVMCallStackFrame *urecord = MVM_callstack_allocate_frame(tc,
usf->body.work_size, usf->body.env_size);
MVMFrame *uf = &(urecord->frame);
MVM_frame_setup_deopt(tc, uf, usf, ucode);
uf->caller = caller;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Recreated frame '%s' (cuid '%s')\n",
MVM_string_utf8_encode_C_string(tc, usf->body.name),
MVM_string_utf8_encode_C_string(tc, usf->body.cuuid));
#endif
/* Copy the locals and lexicals into place. */
if (usf->body.num_locals)
memcpy(uf->work, f->work + cand->body.inlines[i].locals_start,
usf->body.num_locals * sizeof(MVMRegister));
if (usf->body.num_lexicals)
memcpy(uf->env, f->env + cand->body.inlines[i].lexicals_start,
usf->body.num_lexicals * sizeof(MVMRegister));
/* Update our caller's return info. */
caller->return_type = cand->body.inlines[i].res_type;
caller->return_value = caller->return_type == MVM_RETURN_VOID
? NULL
: caller->work + cand->body.inlines[i].res_reg;
caller->return_address = caller->static_info->body.bytecode +
cand->body.deopts[2 * cand->body.inlines[i].return_deopt_idx];
/* Store the callsite, in case we need it for further processing
* of arguments. Do enough to make sure we've got clean enough
* state in the param processing context */
uf->params.arg_info.callsite = cand->body.inlines[i].cs;
uf->params.arg_info.map = (MVMuint16*)(caller->return_address
- cand->body.inlines[i].cs->flag_count * 2);
uf->params.arg_info.source = caller->work;
uf->params.named_used_size = MVM_callsite_num_nameds(tc, cand->body.inlines[i].cs);
/* Store the named argument used bit field, since if we deopt in
* argument handling code we may have missed some. */
if (cand->body.inlines[i].deopt_named_used_bit_field)
uf->params.named_used.bit_field = cand->body.inlines[i].deopt_named_used_bit_field;
}
}
/* By this point, either we did some inlining and the deepest uninlined
* frame is on the top of the callstack, or there was nothing to uninline
* and so we're just in the same frame. Since the deopt target when we
* are in an inline relates to the deepest frame, we can just leave our
* caller to take the appropriate action to move either the interpreter
* or return address to the deopt'd one. */
}
/* We optimize away some bits of args checking; here we re-instate the used named
* arguments bit field, which is required in unoptimized code. */
static void deopt_named_args_used(MVMThreadContext *tc, MVMFrame *f) {
if (f->spesh_cand->body.deopt_named_used_bit_field)
f->params.named_used.bit_field = f->spesh_cand->body.deopt_named_used_bit_field;
}
/* Materialize an individual replaced object. */
static void materialize_object(MVMThreadContext *tc, MVMFrame *f, MVMObject ***materialized,
MVMuint16 info_idx, MVMuint16 target_reg) {
MVMSpeshCandidate *cand = f->spesh_cand;
if (!*materialized)
*materialized = MVM_calloc(MVM_VECTOR_ELEMS(cand->body.deopt_pea.materialize_info), sizeof(MVMObject *));
if (!(*materialized)[info_idx]) {
MVMSpeshPEAMaterializeInfo *mi = &(cand->body.deopt_pea.materialize_info[info_idx]);
MVMSTable *st = (MVMSTable *)cand->body.spesh_slots[mi->stable_sslot];
MVMP6opaqueREPRData *repr_data = (MVMP6opaqueREPRData *)st->REPR_data;
MVMROOT2(tc, f, cand, {
MVMObject *obj = MVM_gc_allocate_object(tc, st);
char *data = (char *)OBJECT_BODY(obj);
MVMuint32 num_attrs = repr_data->num_attributes;
MVMuint32 i;
for (i = 0; i < num_attrs; i++) {
MVMRegister value = f->work[mi->attr_regs[i]];
MVMuint16 offset = repr_data->attribute_offsets[i];
MVMSTable *flattened = repr_data->flattened_stables[i];
if (flattened) {
const MVMStorageSpec *ss = flattened->REPR->get_storage_spec(tc, flattened);
switch (ss->boxed_primitive) {
case MVM_STORAGE_SPEC_BP_INT:
flattened->REPR->box_funcs.set_int(tc, flattened, obj,
(char *)data + offset, value.i64);
break;
case MVM_STORAGE_SPEC_BP_NUM:
flattened->REPR->box_funcs.set_num(tc, flattened, obj,
(char *)data + offset, value.n64);
break;
case MVM_STORAGE_SPEC_BP_STR:
flattened->REPR->box_funcs.set_str(tc, flattened, obj,
(char *)data + offset, value.s);
break;
default:
MVM_panic(1, "Unimplemented case of native attribute deopt materialization");
}
}
else {
*((MVMObject **)(data + offset)) = value.o;
}
}
(*materialized)[info_idx] = obj;
});
#if MVM_LOG_DEOPTS
fprintf(stderr, " Materialized a %s\n", st->debug_name);
#endif
}
f->work[target_reg].o = (*materialized)[info_idx];
}
/* Materialize all replaced objects that need to be at this deopt index. */
static void materialize_replaced_objects(MVMThreadContext *tc, MVMFrame *f, MVMint32 deopt_index) {
MVMuint32 i;
MVMSpeshCandidate *cand = f->spesh_cand;
MVMuint32 num_deopt_points = MVM_VECTOR_ELEMS(cand->body.deopt_pea.deopt_point);
MVMObject **materialized = NULL;
MVMROOT2(tc, f, cand, {
for (i = 0; i < num_deopt_points; i++) {
MVMSpeshPEADeoptPoint *dp = &(cand->body.deopt_pea.deopt_point[i]);
if (dp->deopt_point_idx == deopt_index)
materialize_object(tc, f, &materialized, dp->materialize_info_idx, dp->target_reg);
}
});
MVM_free(materialized);
}
/* Perform actions common to the deopt of a frame before we do any kind of
* address rewriting, whether eager or lazy. */
static void begin_frame_deopt(MVMThreadContext *tc, MVMFrame *f, MVMuint32 deopt_idx) {
deopt_named_args_used(tc, f);
clear_dynlex_cache(tc, f);
/* Materialize any replaced objects first, then if we have stuff replaced
* in inlines then uninlining will take care of moving it out into the
* frames where it belongs. */
materialize_replaced_objects(tc, f, deopt_idx);
}
/* Perform actions common to the deopt of a frame after we do any kind of
* address rewriting, whether eager or lazy. */
static void finish_frame_deopt(MVMThreadContext *tc, MVMFrame *f) {
f->effective_spesh_slots = NULL;
f->spesh_cand = NULL;
f->jit_entry_label = NULL;
}
/* De-optimizes the currently executing frame, provided it is specialized and
* at a valid de-optimization point. Typically used when a guard fails. */
void MVM_spesh_deopt_one(MVMThreadContext *tc, MVMuint32 deopt_idx) {
MVMFrame *f = tc->cur_frame;
if (tc->instance->profiling)
MVM_profiler_log_deopt_one(tc);
#if MVM_LOG_DEOPTS
fprintf(stderr, "Deopt one requested by interpreter in frame '%s' (cuid '%s')\n",
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.cuuid));
#endif
assert(f->spesh_cand != NULL);
assert(deopt_idx < f->spesh_cand->body.num_deopts);
if (f->spesh_cand) {
MVMuint32 deopt_target = f->spesh_cand->body.deopts[deopt_idx * 2];
MVMuint32 deopt_offset = MVM_spesh_deopt_bytecode_pos(f->spesh_cand->body.deopts[deopt_idx * 2 + 1]);
MVMint32 is_pre = MVM_spesh_deopt_is_pre(f->spesh_cand->body.deopts[deopt_idx * 2 + 1]);
#if MVM_LOG_DEOPTS
fprintf(stderr, " Will deopt %u -> %u\n", deopt_offset, deopt_target);
#endif
MVMFrame *top_frame;
MVMROOT(tc, f, {
begin_frame_deopt(tc, f, deopt_idx);
/* Perform any uninlining. */
if (f->spesh_cand->body.inlines) {
/* Perform uninlining. The top frame may have changes, so sync things
* up. */
uninline(tc, f, f->spesh_cand, deopt_offset, 0, is_pre);
top_frame = MVM_callstack_current_frame(tc);
tc->cur_frame = top_frame;
*(tc->interp_reg_base) = top_frame->work;
*(tc->interp_cu) = top_frame->static_info->body.cu;
}
else {
/* No uninlining, so we know the top frame didn't change. */
top_frame = f;
}
});
/* Move the program counter of the interpreter. */
*(tc->interp_cur_op) = top_frame->static_info->body.bytecode + deopt_target;
*(tc->interp_bytecode_start) = top_frame->static_info->body.bytecode;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Completed deopt_one in '%s' (cuid '%s')\n",
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.cuuid));
#endif
finish_frame_deopt(tc, f);
}
else {
MVM_oops(tc, "deopt_one failed for %s (%s)",
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.cuuid));
}
MVM_CHECK_CALLER_CHAIN(tc, tc->cur_frame);
}
/* Walk the call stack, excluding the current frame, looking for specialized
* call frames. If we find them, mark them as needing to be lazily deopt'd
* when unwind reaches them. (This allows us to only ever deopt the stack
* top.) */
void MVM_spesh_deopt_all(MVMThreadContext *tc) {
/* Logging/profiling for global deopt. */
#if MVM_LOG_DEOPTS
fprintf(stderr, "Deopt all requested in frame '%s' (cuid '%s')\n",
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, tc->cur_frame->static_info->body.cuuid));
#endif
if (tc->instance->profiling)
MVM_profiler_log_deopt_all(tc);
/* Create iterator and skip a frame. */
MVMCallStackIterator iter;
MVM_callstack_iter_frame_init(tc, &iter, tc->stack_top);
if (!MVM_callstack_iter_move_next(tc, &iter))
return;
/* Go throught the frames looking for specialized, non-deopt, ones. */
while (MVM_callstack_iter_move_next(tc, &iter)) {
MVMCallStackRecord *record = MVM_callstack_iter_current(tc, &iter);
if (record->kind != MVM_CALLSTACK_RECORD_DEOPT_FRAME) {
MVMFrame *frame = MVM_callstack_record_to_frame(record);
if (frame->spesh_cand) {
/* Needs deoptimizing; mark it as such. */
record->orig_kind = record->kind;
record->kind = MVM_CALLSTACK_RECORD_DEOPT_FRAME;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Marked frame '%s' (cuid '%s') for lazy deopt\n",
MVM_string_utf8_encode_C_string(tc, frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, frame->static_info->body.cuuid));
#endif
}
}
}
}
/* Takes a frame that we're lazily deoptimizing and finds the currently
* active deopt index at the point of the call it was making. Returns -1 if
* none can be resolved. */
MVMint32 MVM_spesh_deopt_find_inactive_frame_deopt_idx(MVMThreadContext *tc,
MVMFrame *f, MVMSpeshCandidate *spesh_cand)
{
/* Is it JITted code? */
if (spesh_cand->body.jitcode) {
MVMJitCode *jitcode = spesh_cand->body.jitcode;
MVMuint32 idx = MVM_jit_code_get_active_deopt_idx(tc, jitcode, f);
if (idx < jitcode->num_deopts) {
MVMint32 deopt_idx = jitcode->deopts[idx].idx;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Found deopt label for JIT (idx %d)\n", deopt_idx);
#endif
return deopt_idx;
}
}
else {
/* Not JITted; see if we can find the return address in the deopt table. */
MVMuint32 ret_offset = (f == tc->cur_frame ? *(tc->interp_cur_op) : f->return_address) - spesh_cand->body.bytecode;
MVMint32 n = spesh_cand->body.num_deopts * 2;
MVMint32 i;
for (i = 0; i < n; i += 2) {
if (MVM_spesh_deopt_bytecode_pos(spesh_cand->body.deopts[i + 1]) == ret_offset) {
MVMint32 deopt_idx = i / 2;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Found deopt index for interpeter (idx %d)\n", deopt_idx);
#endif
return deopt_idx;
}
}
}
#if MVM_LOG_DEOPTS
fprintf(stderr, " Can't find deopt all idx\n");
#endif
return -1;
}
/* Called during stack unwinding when we reach a frame that was marked as
* needing to be deoptimized lazily. Performs that deoptimization. Note
* that this may actually modify the call stack by adding new records on
* top of it, if we have to uninline. */
void MVM_spesh_deopt_during_unwind(MVMThreadContext *tc) {
/* Get the frame from the record. If we're calling this, we know it's the
* stack top one. */
MVMCallStackRecord *record = tc->stack_top;
MVMFrame *frame = MVM_callstack_record_to_frame(record);
MVMSpeshCandidate *spesh_cand = frame->spesh_cand;
#if MVM_LOG_DEOPTS
fprintf(stderr, "Lazy deopt on unwind of frame '%s' (cuid '%s')\n",
MVM_string_utf8_encode_C_string(tc, frame->static_info->body.name),
MVM_string_utf8_encode_C_string(tc, frame->static_info->body.cuuid));
#endif
/* Find the deopt index, and assuming it's found, deopt. */
MVMint32 deopt_idx = MVM_spesh_deopt_find_inactive_frame_deopt_idx(tc, frame, spesh_cand);
if (deopt_idx >= 0) {
MVMuint32 deopt_target = spesh_cand->body.deopts[deopt_idx * 2];
MVMuint32 deopt_offset = MVM_spesh_deopt_bytecode_pos(spesh_cand->body.deopts[deopt_idx * 2 + 1]);
MVMFrame *top_frame;
MVMROOT(tc, frame, {
begin_frame_deopt(tc, frame, deopt_idx);
/* Potentially need to uninline. This leaves the top frame being the
* one we're returning into. Otherwise, the top frame is the current
* one. */
if (spesh_cand->body.inlines) {
uninline(tc, frame, spesh_cand, deopt_offset, 1, 0);
top_frame = MVM_callstack_current_frame(tc);
}
else {
top_frame = frame;
}
});
/* Rewrite return address in the current top frame and sync current
* frame. */
top_frame->return_address = top_frame->static_info->body.bytecode + deopt_target;
#if MVM_LOG_DEOPTS
fprintf(stderr, " Deopt %u -> %u without uninlining\n", deopt_offset, deopt_target);
#endif
tc->cur_frame = top_frame;
finish_frame_deopt(tc, frame);
}
/* Sync interpreter so it's ready to continue running this deoptimized
* frame. */
*(tc->interp_cur_op) = tc->cur_frame->return_address;
*(tc->interp_bytecode_start) = MVM_frame_effective_bytecode(tc->cur_frame);
*(tc->interp_reg_base) = tc->cur_frame->work;
*(tc->interp_cu) = tc->cur_frame->static_info->body.cu;
/* Update the record to indicate we're no long in need of deopt. */
record->kind = record->orig_kind;
}