Reviewers: fschneider,
Message:
It turned out that my original CL that replaces ClearOperands in GVN had a
bug,
which I fixed. So now doing the same for RemovePhi works too. Mjsunit,
Mozilla
and Sputnik tests all pass in debug mode.
PTAL.
Description:
Speed up removing phi nodes.
BUG=
TEST=
Please review this at http://codereview.chromium.org/9452022/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/hydrogen-instructions.h
M src/hydrogen-instructions.cc
M src/hydrogen.cc
Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index
3b0b367da8674fc6442984e0fe01001bb7e98aae..2b744eede4898accea98f3ea22717e2584c8ae68
100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -383,19 +383,7 @@ void HValue::DeleteAndReplaceWith(HValue* other) {
// We replace all uses first, so Delete can assert that there are none.
if (other != NULL) ReplaceAllUsesWith(other);
ASSERT(HasNoUses());
- // Clearing the operands includes going through the use list of each
operand
- // to remove this HValue, which can be expensive. Instead, we mark this
as
- // dead and only check the first item in the use list of each operand.
- // For the following items in the use lists we rely on the tail() method
to
- // skip dead dead items and remove them lazily.
- SetFlag(kIsDead);
- for (int i = 0; i < OperandCount(); ++i) {
- HValue* operand = OperandAt(i);
- HUseListNode* first = operand->use_list_;
- if (first != NULL && first->index() == i && first->value() == this) {
- operand->use_list_ = first->tail();
- }
- }
+ Kill();
DeleteFromGraph();
}
@@ -413,9 +401,17 @@ void HValue::ReplaceAllUsesWith(HValue* other) {
}
-void HValue::ClearOperands() {
+void HValue::Kill() {
+ // Instead of going through the entire use list of each operand, we only
+ // check the first item in each use list and rely on the tail() method to
+ // skip dead items, removing them lazily next time we traverse the list.
+ SetFlag(kIsDead);
for (int i = 0; i < OperandCount(); ++i) {
- SetOperandAt(i, NULL);
+ HValue* operand = OperandAt(i);
+ HUseListNode* first = operand->use_list_;
+ if (first != NULL && first->index() == i && first->value() == this) {
+ operand->use_list_ = first->tail();
+ }
}
}
Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index
4a01085043960f0881b3a28edee51c5c606b4ced..011529d6cdfd94f85f2029b93e93ee07333d6e19
100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -631,7 +631,9 @@ class HValue: public ZoneObject {
return use_list_ != NULL && use_list_->tail() != NULL;
}
int UseCount() const;
- void ClearOperands();
+
+ // Mark this HValue as dead and to be removed from other HValues' use
lists.
+ void Kill();
int flags() const { return flags_; }
void SetFlag(Flag f) { flags_ |= (1 << f); }
Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index
9918e8518096044441006ae7a39ec0fe137b169d..6bc8af595d2eb26ac0fb069351560dbf8faad410
100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -97,7 +97,7 @@ void HBasicBlock::RemovePhi(HPhi* phi) {
ASSERT(phi->block() == this);
ASSERT(phis_.Contains(phi));
ASSERT(phi->HasNoUses() || !phi->is_live());
- phi->ClearOperands();
+ phi->Kill();
phis_.RemoveElement(phi);
phi->SetBlock(NULL);
}
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