Reviewers: danno, fschneider,
Description:
Re-use phi reachability information to avoid a fixed-point computation.
When we propagate the information that a value is not convertible to
integer,
there is no need for a separate fixed-point computation, we can do things
the
"Millikin way" (tm), folding as much computation as possible into a single
pass:
;-) We already have the phi node reachability information, so we can easily
propagate this while doing the representation histogram computation.
Please review this at http://codereview.chromium.org/7754010/
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/hydrogen-instructions.h
M src/hydrogen.cc
Index: src/hydrogen-instructions.h
===================================================================
--- src/hydrogen-instructions.h (revision 9185)
+++ src/hydrogen-instructions.h (working copy)
@@ -2209,6 +2209,13 @@
is_convertible_to_integer_ = b;
}
+ bool AllOperandsConvertibleToInteger() {
+ for (int i = 0; i < OperandCount(); ++i) {
+ if (!OperandAt(i)->IsConvertibleToInteger()) return false;
+ }
+ return true;
+ }
+
protected:
virtual void DeleteFromGraph();
virtual void InternalSetOperandAt(int index, HValue* value) {
Index: src/hydrogen.cc
===================================================================
--- src/hydrogen.cc (revision 9185)
+++ src/hydrogen.cc (working copy)
@@ -1690,38 +1690,24 @@
}
}
- // (3) Sum up the non-phi use counts of all connected phis. Don't
include
- // the non-phi uses of the phi itself.
+ // (3) Use the phi reachability information from step 2 to
+ // (a) sum up the non-phi use counts of all connected phis.
+ // (b) push information about values which can't be converted to
integer
+ // without deoptimization through the phi use-def chains,
avoiding
+ // unnecessary deoptimizations later.
for (int i = 0; i < phi_count; ++i) {
HPhi* phi = phi_list->at(i);
+ bool cti = phi->AllOperandsConvertibleToInteger();
for (BitVector::Iterator it(connected_phis.at(i));
!it.Done();
it.Advance()) {
int index = it.Current();
- if (index != i) {
- HPhi* it_use = phi_list->at(it.Current());
- phi->AddNonPhiUsesFrom(it_use);
- }
+ HPhi* it_use = phi_list->at(it.Current());
+ if (index != i) phi->AddNonPhiUsesFrom(it_use); // Don't count
twice!
+ if (!cti) it_use->set_is_convertible_to_integer(false);
}
}
- // (4) Compute phis that definitely can't be converted to integer
- // without deoptimization and mark them to avoid unnecessary
deoptimization.
- change = true;
- while (change) {
- change = false;
- for (int i = 0; i < phi_count; ++i) {
- HPhi* phi = phi_list->at(i);
- for (int j = 0; j < phi->OperandCount(); ++j) {
- if (phi->IsConvertibleToInteger() &&
- !phi->OperandAt(j)->IsConvertibleToInteger()) {
- phi->set_is_convertible_to_integer(false);
- change = true;
- break;
- }
- }
- }
- }
for (int i = 0; i < graph_->blocks()->length(); ++i) {
--
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