Reviewers: Toon Verwaest,
https://codereview.chromium.org/106973005/diff/1/src/hydrogen-load-elimination.cc
File src/hydrogen-load-elimination.cc (left):
https://codereview.chromium.org/106973005/diff/1/src/hydrogen-load-elimination.cc#oldcode46
src/hydrogen-load-elimination.cc:46: HLoadNamedField* last_load_;
Note that this field was really only used for debugging, so I am going
ahead and removing it in this CL.
Description:
Improve load elimination handling of transitioning stores.
BUG=
Please review this at https://codereview.chromium.org/106973005/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+6, -10 lines):
M src/hydrogen-load-elimination.cc
Index: src/hydrogen-load-elimination.cc
diff --git a/src/hydrogen-load-elimination.cc
b/src/hydrogen-load-elimination.cc
index
f3b574847f8e3ed6b9e5807fa0cee894b18af41b..f2e993b18dea2305884acd01274f85edab887260
100644
--- a/src/hydrogen-load-elimination.cc
+++ b/src/hydrogen-load-elimination.cc
@@ -43,7 +43,6 @@ static const int kMaxTrackedObjects = 5;
class HFieldApproximation : public ZoneObject {
public: // Just a data blob.
HValue* object_;
- HLoadNamedField* last_load_;
HValue* last_value_;
HFieldApproximation* next_;
@@ -52,7 +51,6 @@ class HFieldApproximation : public ZoneObject {
if (this == NULL) return NULL;
HFieldApproximation* copy = new(zone) HFieldApproximation();
copy->object_ = this->object_;
- copy->last_load_ = this->last_load_;
copy->last_value_ = this->last_value_;
copy->next_ = this->next_->Copy(zone);
return copy;
@@ -197,7 +195,6 @@ class HLoadEliminationTable : public ZoneObject {
if (approx->last_value_ == NULL) {
// Load is not redundant. Fill out a new entry.
- approx->last_load_ = instr;
approx->last_value_ = instr;
return instr;
} else {
@@ -217,12 +214,14 @@ class HLoadEliminationTable : public ZoneObject {
HValue* object = instr->object()->ActualValue();
HValue* value = instr->value();
- // Kill non-equivalent may-alias entries.
- KillFieldInternal(object, field, value);
if (instr->has_transition()) {
- // A transition store alters the map of the object.
- // TODO(titzer): remember the new map (a constant) for the object.
+ // A transition introduces a new field and alters the map of the
object.
+ // Since the field in the object is new, it cannot alias existing
entries.
+ // TODO(titzer): introduce a constant for the new map and remember
it.
KillFieldInternal(object, FieldOf(JSObject::kMapOffset), NULL);
+ } else {
+ // Kill non-equivalent may-alias entries.
+ KillFieldInternal(object, field, value);
}
HFieldApproximation* approx = FindOrCreate(object, field);
@@ -231,7 +230,6 @@ class HLoadEliminationTable : public ZoneObject {
return NULL;
} else {
// The store is not redundant. Update the entry.
- approx->last_load_ = NULL;
approx->last_value_ = value;
return instr;
}
@@ -314,7 +312,6 @@ class HLoadEliminationTable : public ZoneObject {
// Insert the entry at the head of the list.
approx->object_ = object;
- approx->last_load_ = NULL;
approx->last_value_ = NULL;
approx->next_ = fields_[field];
fields_[field] = approx;
@@ -397,7 +394,6 @@ class HLoadEliminationTable : public ZoneObject {
PrintF(" field %d: ", i);
for (HFieldApproximation* a = fields_[i]; a != NULL; a = a->next_) {
PrintF("[o%d =", a->object_->id());
- if (a->last_load_ != NULL) PrintF(" L%d", a->last_load_->id());
if (a->last_value_ != NULL) PrintF(" v%d", a->last_value_->id());
PrintF("] ");
}
--
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