Revision: 19102
Author: [email protected]
Date: Wed Feb 5 13:39:55 2014 UTC
Log: Check elimination improvement: propagation of state through phis
is supported, CheckMap narrowing implemented.
[email protected]
Review URL: https://codereview.chromium.org/141653009
http://code.google.com/p/v8/source/detail?r=19102
Modified:
/branches/bleeding_edge/src/hydrogen-check-elimination.cc
/branches/bleeding_edge/src/hydrogen-instructions.h
=======================================
--- /branches/bleeding_edge/src/hydrogen-check-elimination.cc Wed Feb 5
09:30:53 2014 UTC
+++ /branches/bleeding_edge/src/hydrogen-check-elimination.cc Wed Feb 5
13:39:55 2014 UTC
@@ -48,12 +48,12 @@
struct HCheckTableEntry {
HValue* object_; // The object being approximated. NULL => invalid
entry.
- HValue* check_; // The last check instruction.
- MapSet maps_; // The set of known maps for the object.
+ HInstruction* check_; // The last check instruction.
+ MapSet maps_; // The set of known maps for the object.
};
-// The main datastructure used during check elimination, which stores a
+// The main data structure used during check elimination, which stores a
// set of known maps for each object.
class HCheckTable : public ZoneObject {
public:
@@ -129,6 +129,23 @@
}
copy->cursor_ = cursor_;
copy->size_ = size_;
+
+ // Create entries for succ block's phis.
+ if (succ->phis()->length() > 0) {
+ int pred_index = succ->PredecessorIndexOf(from_block);
+ for (int phi_index = 0;
+ phi_index < succ->phis()->length();
+ ++phi_index) {
+ HPhi* phi = succ->phis()->at(phi_index);
+ HValue* phi_operand = phi->OperandAt(pred_index);
+
+ HCheckTableEntry* pred_entry = copy->Find(phi_operand);
+ if (pred_entry != NULL) {
+ // Create an entry for a phi in the table.
+ copy->Insert(phi, NULL, pred_entry->maps_->Copy(phase_->zone()));
+ }
+ }
+ }
// Branch-sensitive analysis for certain comparisons may add more facts
// to the state for the successor on the true branch.
@@ -185,17 +202,28 @@
// Global analysis: Merge this state with the other incoming state.
HCheckTable* Merge(HBasicBlock* succ, HCheckTable* that,
- HBasicBlock* that_block, Zone* zone) {
- if (that_block->IsReachable()) {
+ HBasicBlock* pred_block, Zone* zone) {
+ if (pred_block->IsReachable()) {
if (that->size_ == 0) {
// If the other state is empty, simply reset.
size_ = 0;
cursor_ = 0;
} else {
+ int pred_index = succ->PredecessorIndexOf(pred_block);
bool compact = false;
for (int i = 0; i < size_; i++) {
HCheckTableEntry* this_entry = &entries_[i];
- HCheckTableEntry* that_entry = that->Find(this_entry->object_);
+ HCheckTableEntry* that_entry;
+ if (this_entry->object_->IsPhi() &&
+ this_entry->object_->block() == succ) {
+ HPhi* phi = HPhi::cast(this_entry->object_);
+ HValue* phi_operand = phi->OperandAt(pred_index);
+ that_entry = that->Find(phi_operand);
+
+ } else {
+ that_entry = that->Find(this_entry->object_);
+ }
+
if (that_entry == NULL) {
this_entry->object_ = NULL;
compact = true;
@@ -213,7 +241,7 @@
}
if (FLAG_trace_check_elimination) {
PrintF("B%d checkmaps-table merged with B%d table:\n",
- succ->block_id(), that_block->block_id());
+ succ->block_id(), pred_block->block_id());
Print();
}
return this;
@@ -244,14 +272,42 @@
}
return;
}
- i = i->Intersect(a, phase_->zone());
- if (i->size() == 0) {
+ MapSet intersection = i->Intersect(a, phase_->zone());
+ if (intersection->size() == 0) {
// Intersection is empty; probably megamorphic, which is likely to
// deopt anyway, so just leave things as they are.
INC_STAT(empty_);
} else {
- // TODO(titzer): replace the first check with a more strict check
- INC_STAT(narrowed_);
+ // Update set of maps in the entry.
+ entry->maps_ = intersection;
+ if (intersection->size() != i->size()) {
+ // Narrow set of maps in the second check maps instruction.
+ HGraph* graph = instr->block()->graph();
+ HCheckMaps* new_check_maps =
+ HCheckMaps::New(graph->zone(), NULL, instr->value(),
+ intersection, instr->typecheck());
+ if (entry->check_ != NULL &&
+ entry->check_->block() == instr->block()) {
+ // There is a check in the same block so replace it with a more
+ // strict check and eliminate the second check entirely.
+ new_check_maps->InsertBefore(entry->check_);
+ entry->check_->DeleteAndReplaceWith(new_check_maps);
+ TRACE(("Check #%d narrowed to #%d\n",
+ entry->check_->id(), new_check_maps->id()));
+
+ } else {
+ new_check_maps->InsertBefore(instr);
+ }
+ TRACE(("CheckMaps #%d for #%d narrowed to #%d:\n",
+ instr->id(), instr->value()->id(), new_check_maps->id()));
+ instr->DeleteAndReplaceWith(new_check_maps);
+ entry->check_ = new_check_maps;
+
+ if (FLAG_trace_check_elimination) {
+ Print();
+ }
+ INC_STAT(narrowed_);
+ }
}
} else {
// No entry; insert a new one.
@@ -426,7 +482,9 @@
for (int i = 0; i < size_; i++) {
HCheckTableEntry* entry = &entries_[i];
ASSERT(entry->object_ != NULL);
- PrintF(" checkmaps-table @%d: object #%d ", i,
entry->object_->id());
+ PrintF(" checkmaps-table @%d: %s #%d ", i,
+ entry->object_->IsPhi() ? "phi" : "object",
+ entry->object_->id());
if (entry->check_ != NULL) {
PrintF("check #%d ", entry->check_->id());
}
=======================================
--- /branches/bleeding_edge/src/hydrogen-instructions.h Wed Feb 5 09:30:53
2014 UTC
+++ /branches/bleeding_edge/src/hydrogen-instructions.h Wed Feb 5 13:39:55
2014 UTC
@@ -2657,6 +2657,15 @@
}
return check_map;
}
+ static HCheckMaps* New(Zone* zone, HValue* context,
+ HValue* value, UniqueSet<Map>* maps,
+ HValue *typecheck = NULL) {
+ HCheckMaps* check_map = new(zone) HCheckMaps(value, zone, typecheck);
+ for (int i = 0; i < maps->size(); i++) {
+ check_map->Add(maps->at(i).handle(), zone);
+ }
+ return check_map;
+ }
bool CanOmitMapChecks() { return omit_; }
@@ -2669,6 +2678,7 @@
virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
HValue* value() { return OperandAt(0); }
+ HValue* typecheck() { return OperandAt(1); }
Unique<Map> first_map() const { return map_set_.at(0); }
UniqueSet<Map> map_set() const { return map_set_; }
--
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