Reviewers: Igor Sheludko, titzer,
Message:
PTAL
Description:
Don't propagate information through phis in loop headers.
To properly do this, we'd have to iterate over CompareMaps (and their
bodies)
handling phis, until we have learned enough to decide which paths can be
taken.
For now, just disable learning from phis in loop headers.
BUG=
Please review this at https://codereview.chromium.org/147023005/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files (+22, -1 lines):
M src/hydrogen-check-elimination.cc
A test/mjsunit/regress/regress-check-eliminate-loop-phis.js
Index: src/hydrogen-check-elimination.cc
diff --git a/src/hydrogen-check-elimination.cc
b/src/hydrogen-check-elimination.cc
index
5fdb3e3f3c48fa1260005eeeab7ec7e6ae537ebd..59b1b266844d455b9042d0505057013de47d3b4d
100644
--- a/src/hydrogen-check-elimination.cc
+++ b/src/hydrogen-check-elimination.cc
@@ -164,7 +164,7 @@ class HCheckTable : public ZoneObject {
copy->size_ = size_;
// Create entries for succ block's phis.
- if (succ->phis()->length() > 0) {
+ if (!succ->IsLoopHeader() && succ->phis()->length() > 0) {
int pred_index = succ->PredecessorIndexOf(from_block);
for (int phi_index = 0;
phi_index < succ->phis()->length();
Index: test/mjsunit/regress/regress-check-eliminate-loop-phis.js
diff --git a/test/mjsunit/regress/regress-check-eliminate-loop-phis.js
b/test/mjsunit/regress/regress-check-eliminate-loop-phis.js
new file mode 100644
index
0000000000000000000000000000000000000000..f4d8ae719f253e74f7cdd508aecaa90dc76a847d
--- /dev/null
+++ b/test/mjsunit/regress/regress-check-eliminate-loop-phis.js
@@ -0,0 +1,21 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function f() {
+ var o = {x:1};
+ var y = {y:2.5, x:0};
+ var result;
+ for (var i = 0; i < 2; i++) {
+ result = o.x + 3;
+ o = y;
+ }
+ return result;
+}
+
+f();
+f();
+%OptimizeFunctionOnNextCall(f);
+print(f());
--
--
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