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Fix handling of added deopt points
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During call optimization, we might choose to insert extra deopting
instructions, each which get their own annotation. However, we were
leaving the original annotation then on a prepargs, which is not a
deopt-causing instruction, so we would wrongly drop use of the deopt
point. Fix by establishing a link between those added "synthetic"
deopt points and the original one they stole the target address from.
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@jnthn
jnthn committed Jul 13, 2018
1 parent 787b7bb commit 3345ec3
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Showing 5 changed files with 96 additions and 13 deletions.
4 changes: 4 additions & 0 deletions src/spesh/dump.c
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Expand Up @@ -185,6 +185,10 @@ static void dump_bb(MVMThreadContext *tc, DumpStr *ds, MVMSpeshGraph *g, MVMSpes
appendf(ds, " [Annotation: Logged (bytecode offset %d)]\n",
ann->data.bytecode_offset);
break;
case MVM_SPESH_ANN_DEOPT_SYNTH:
appendf(ds, " [Annotation: INS Deopt Synth (idx %d)]\n",
ann->data.deopt_idx);
break;
default:
appendf(ds, " [Annotation: %d (unknown)]\n", ann->type);
}
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1 change: 1 addition & 0 deletions src/spesh/graph.h
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Expand Up @@ -252,6 +252,7 @@ struct MVMSpeshAnn {
#define MVM_SPESH_ANN_DEOPT_OSR 9
#define MVM_SPESH_ANN_LINENO 10
#define MVM_SPESH_ANN_LOGGED 11
#define MVM_SPESH_ANN_DEOPT_SYNTH 12

/* Functions to create/destroy the spesh graph. */
MVMSpeshGraph * MVM_spesh_graph_create(MVMThreadContext *tc, MVMStaticFrame *sf,
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50 changes: 37 additions & 13 deletions src/spesh/optimize.c
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Expand Up @@ -1312,12 +1312,15 @@ MVMuint32 find_invoke_offset(MVMThreadContext *tc, MVMSpeshIns *ins) {

/* Given an instruction, finds the deopt target on it. Panics if there is not
* one there. */
MVMuint32 find_deopt_target(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshIns *ins) {
MVMuint32 deopt_target;
void find_deopt_target_and_index(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshIns *ins,
MVMint32 *deopt_target_out, MVMint32 *deopt_index_out) {
MVMSpeshAnn *deopt_ann = ins->annotations;
while (deopt_ann) {
if (deopt_ann->type == MVM_SPESH_ANN_DEOPT_ONE_INS)
return g->deopt_addrs[2 * deopt_ann->data.deopt_idx];
if (deopt_ann->type == MVM_SPESH_ANN_DEOPT_ONE_INS) {
*deopt_target_out = g->deopt_addrs[2 * deopt_ann->data.deopt_idx];
*deopt_index_out = deopt_ann->data.deopt_idx;
return;
}
deopt_ann = deopt_ann->next;
}
MVM_panic(1, "Spesh: unexpectedly missing deopt annotation on prepargs");
Expand Down Expand Up @@ -1378,12 +1381,24 @@ static MVMSpeshStatsType * find_invokee_type_tuple(MVMThreadContext *tc, MVMSpes
: NULL;
}

/* Adds an annotation relating a synthetic (added during optimization) deopt
* point back to the original one whose usages will have been recorded in the
* facts. */
static void add_synthetic_deopt_annotation(MVMThreadContext *tc, MVMSpeshGraph *g,
MVMSpeshIns *ins, MVMuint32 deopt_index) {
MVMSpeshAnn *ann = MVM_spesh_alloc(tc, g, sizeof(MVMSpeshAnn));
ann->type = MVM_SPESH_ANN_DEOPT_SYNTH;
ann->data.deopt_idx = deopt_index;
ann->next = ins->annotations;
ins->annotations = ann;
}

/* Inserts an argument type guard as suggested by a logged type tuple. */
static void insert_arg_type_guard(MVMThreadContext *tc, MVMSpeshGraph *g,
MVMSpeshStatsType *type_info,
MVMSpeshCallInfo *arg_info, MVMuint32 arg_idx) {
/* Insert guard before prepargs (this means they stack up in order). */
MVMuint32 deopt_target = find_deopt_target(tc, g, arg_info->prepargs_ins);
MVMuint32 deopt_target, deopt_index;
MVMSpeshIns *guard = MVM_spesh_alloc(tc, g, sizeof(MVMSpeshIns));
guard->info = MVM_op_get_op(type_info->type_concrete
? MVM_OP_sp_guardconc
Expand All @@ -1392,22 +1407,25 @@ static void insert_arg_type_guard(MVMThreadContext *tc, MVMSpeshGraph *g,
guard->operands[0] = arg_info->arg_ins[arg_idx]->operands[1];
guard->operands[1].lit_i16 = MVM_spesh_add_spesh_slot_try_reuse(tc, g,
(MVMCollectable *)type_info->type->st);
find_deopt_target_and_index(tc, g, arg_info->prepargs_ins, &deopt_target, &deopt_index);
guard->operands[2].lit_ui32 = deopt_target;
MVM_spesh_manipulate_insert_ins(tc, arg_info->prepargs_bb,
arg_info->prepargs_ins->prev, guard);
MVM_spesh_usages_add_by_reg(tc, g, arg_info->arg_ins[arg_idx]->operands[1], guard);

/* Also give the instruction a deopt annotation. */
/* Also give the instruction a deopt annotation, and related it to the
* one on the prepargs. */
MVM_spesh_graph_add_deopt_annotation(tc, g, guard, deopt_target,
MVM_SPESH_ANN_DEOPT_ONE_INS);
add_synthetic_deopt_annotation(tc, g, guard, deopt_index);
}

/* Inserts an argument decont type guard as suggested by a logged type tuple. */
static void insert_arg_decont_type_guard(MVMThreadContext *tc, MVMSpeshGraph *g,
MVMSpeshStatsType *type_info,
MVMSpeshCallInfo *arg_info, MVMuint32 arg_idx) {
MVMSpeshIns *decont, *guard;
MVMuint32 deopt_target;
MVMuint32 deopt_target, deopt_index;

/* We need a temporary register to decont into. */
MVMSpeshOperand temp = MVM_spesh_manipulate_get_temp_reg(tc, g, MVM_reg_obj);
Expand All @@ -1425,7 +1443,7 @@ static void insert_arg_decont_type_guard(MVMThreadContext *tc, MVMSpeshGraph *g,
optimize_decont(tc, g, arg_info->prepargs_bb, decont);

/* Guard the decontainerized value. */
deopt_target = find_deopt_target(tc, g, arg_info->prepargs_ins);
find_deopt_target_and_index(tc, g, arg_info->prepargs_ins, &deopt_target, &deopt_index);
guard = MVM_spesh_alloc(tc, g, sizeof(MVMSpeshIns));
guard->info = MVM_op_get_op(type_info->decont_type_concrete
? MVM_OP_sp_guardconc
Expand All @@ -1439,9 +1457,11 @@ static void insert_arg_decont_type_guard(MVMThreadContext *tc, MVMSpeshGraph *g,
arg_info->prepargs_ins->prev, guard);
MVM_spesh_usages_add_by_reg(tc, g, temp, guard);

/* Also give the instruction a deopt annotation. */
/* Also give the instruction a deopt annotation and reference prepargs
* deopt index. */
MVM_spesh_graph_add_deopt_annotation(tc, g, guard, deopt_target,
MVM_SPESH_ANN_DEOPT_ONE_INS);
add_synthetic_deopt_annotation(tc, g, guard, deopt_index);

/* Release the temp register. */
MVM_spesh_manipulate_release_temp_reg(tc, g, temp);
Expand Down Expand Up @@ -1545,7 +1565,7 @@ static void tweak_for_target_sf(MVMThreadContext *tc, MVMSpeshGraph *g,
MVMStaticFrame *target_sf, MVMSpeshIns *ins,
MVMSpeshCallInfo *arg_info, MVMSpeshOperand temp) {
MVMSpeshIns *guard, *resolve;
MVMuint32 deopt_target;
MVMuint32 deopt_target, deopt_index;

/* Work out which operand of the invoke instruction has the invokee. */
MVMuint32 inv_code_index = ins->info->opcode == MVM_OP_invoke_v ? 0 : 1;
Expand All @@ -1563,7 +1583,7 @@ static void tweak_for_target_sf(MVMThreadContext *tc, MVMSpeshGraph *g,
MVM_spesh_usages_add_by_reg(tc, g, resolve->operands[1], resolve);

/* Insert guard instruction before the prepargs. */
deopt_target = find_deopt_target(tc, g, arg_info->prepargs_ins);
find_deopt_target_and_index(tc, g, arg_info->prepargs_ins, &deopt_target, &deopt_index);
guard = MVM_spesh_alloc(tc, g, sizeof(MVMSpeshIns));
guard->info = MVM_op_get_op(MVM_OP_sp_guardsf);
guard->operands = MVM_spesh_alloc(tc, g, 3 * sizeof(MVMSpeshOperand));
Expand All @@ -1575,9 +1595,11 @@ static void tweak_for_target_sf(MVMThreadContext *tc, MVMSpeshGraph *g,
MVM_spesh_manipulate_insert_ins(tc, arg_info->prepargs_bb,
arg_info->prepargs_ins->prev, guard);

/* Also give the guard instruction a deopt annotation. */
/* Also give the guard instruction a deopt annotation and reference the
* prepargs annotation. */
MVM_spesh_graph_add_deopt_annotation(tc, g, guard, deopt_target,
MVM_SPESH_ANN_DEOPT_ONE_INS);
add_synthetic_deopt_annotation(tc, g, guard, deopt_index);

/* Make the invoke instruction call the resolved result. */
MVM_spesh_usages_delete_by_reg(tc, g, ins->operands[inv_code_index], ins);
Expand Down Expand Up @@ -1985,11 +2007,12 @@ static void optimize_throwcat(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshBB

/* Updates rebless with rebless_sp, which will deopt from the current code. */
static void tweak_rebless(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshIns *ins) {
MVMuint32 deopt_target = find_deopt_target(tc, g, ins);
MVMuint32 deopt_target, deopt_index;
MVMSpeshOperand *new_operands = MVM_spesh_alloc(tc, g, 4 * sizeof(MVMSpeshOperand));
new_operands[0] = ins->operands[0];
new_operands[1] = ins->operands[1];
new_operands[2] = ins->operands[2];
find_deopt_target_and_index(tc, g, ins, &deopt_target, &deopt_index);
new_operands[3].lit_ui32 = deopt_target;
ins->info = MVM_op_get_op(MVM_OP_sp_rebless);
ins->operands = new_operands;
Expand Down Expand Up @@ -2751,6 +2774,7 @@ void MVM_spesh_optimize(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshPlanned
MVM_spesh_graph_recompute_dominance(tc, g);
eliminate_unused_log_guards(tc, g);
eliminate_pointless_gotos(tc, g);
MVM_spesh_usages_remove_unused_deopt(tc, g);
eliminate_dead_ins(tc, g);

merge_bbs(tc, g);
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53 changes: 53 additions & 0 deletions src/spesh/usages.c
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Expand Up @@ -268,6 +268,59 @@ void MVM_spesh_usages_add_unconditional_deopt_usage_by_reg(MVMThreadContext *tc,
MVM_spesh_usages_add_unconditional_deopt_usage(tc, g, MVM_spesh_get_facts(tc, g, operand));
}

/* Remove usages of deopt points that won't casue deopt. */
void MVM_spesh_usages_remove_unused_deopt(MVMThreadContext *tc, MVMSpeshGraph *g) {
MVMuint32 i, j;

/* First, walk graph to find which deopt points are actually used. */
MVMuint8 *deopt_used = MVM_spesh_alloc(tc, g, g->num_deopt_addrs);
MVMSpeshBB *bb = g->entry;
while (bb) {
if (!bb->inlined) {
MVMSpeshIns *ins = bb->first_ins;
while (ins) {
MVMSpeshAnn *ann = ins->annotations;
while (ann) {
switch (ann->type) {
case MVM_SPESH_ANN_DEOPT_ONE_INS:
case MVM_SPESH_ANN_DEOPT_ALL_INS:
case MVM_SPESH_ANN_DEOPT_SYNTH:
if (ins->info->may_cause_deopt)
deopt_used[ann->data.deopt_idx] = 1;
/* else
printf("Instruction %s cannot cause deopt\n", ins->info->name);*/
break;
}
ann = ann->next;
}
ins = ins->next;
}
}
bb = bb->linear_next;
}

/* Now delete deopt usages that are of unused deopt indices. */
for (i = 0; i < g->sf->body.num_locals; i++) {
for (j = 0; j < g->fact_counts[i]; j++) {
MVMSpeshFacts *facts = &(g->facts[i][j]);
MVMSpeshDeoptUseEntry *du_entry = facts->usage.deopt_users;
MVMSpeshDeoptUseEntry *prev_du_entry = NULL;
while (du_entry) {
if (du_entry->deopt_idx >= 0 && !deopt_used[du_entry->deopt_idx]) {
if (prev_du_entry)
prev_du_entry->next = du_entry->next;
else
facts->usage.deopt_users = du_entry->next;
}
else {
prev_du_entry = du_entry;
}
du_entry = du_entry->next;
}
}
}
}

/* Checks if the value is used, either by another instruction in the graph or
* by being needed for deopt. */
MVMuint32 MVM_spesh_usages_is_used(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshOperand check) {
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1 change: 1 addition & 0 deletions src/spesh/usages.h
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Expand Up @@ -58,6 +58,7 @@ void MVM_spesh_usages_create_deopt_usage(MVMThreadContext *tc, MVMSpeshGraph *g)
void MVM_spesh_usages_add_unconditional_deopt_usage(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshFacts *facts);
void MVM_spesh_usages_add_unconditional_deopt_usage_by_reg(MVMThreadContext *tc, MVMSpeshGraph *g,
MVMSpeshOperand operand);
void MVM_spesh_usages_remove_unused_deopt(MVMThreadContext *tc, MVMSpeshGraph *g);
MVMuint32 MVM_spesh_usages_is_used(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshOperand check);
MVMuint32 MVM_spesh_usages_is_used_by_deopt(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshOperand check);
MVMuint32 MVM_spesh_usages_is_used_by_handler(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshOperand check);
Expand Down

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