Revision: 13042
Author: [email protected]
Date: Fri Nov 23 05:23:39 2012
Log: Force small array literals to have FAST_ELEMENTs
[email protected]
Review URL: https://codereview.chromium.org/11414139
http://code.google.com/p/v8/source/detail?r=13042
Modified:
/branches/bleeding_edge/src/parser.cc
/branches/bleeding_edge/test/mjsunit/array-natives-elements.js
=======================================
--- /branches/bleeding_edge/src/parser.cc Thu Nov 22 02:25:22 2012
+++ /branches/bleeding_edge/src/parser.cc Fri Nov 23 05:23:39 2012
@@ -3718,6 +3718,7 @@
isolate()->factory()->NewFixedArray(values->length(), TENURED);
Handle<FixedDoubleArray> double_literals;
ElementsKind elements_kind = FAST_SMI_ELEMENTS;
+ bool has_only_undefined_values = true;
bool has_hole_values = false;
// Fill in the literals.
@@ -3749,6 +3750,7 @@
// FAST_DOUBLE_ELEMENTS and FAST_ELEMENTS as necessary. Always
remember
// the tagged value, no matter what the ElementsKind is in case we
// ultimately end up in FAST_ELEMENTS.
+ has_only_undefined_values = false;
object_literals->set(i, *boilerplate_value);
if (elements_kind == FAST_SMI_ELEMENTS) {
// Smi only elements. Notice if a transition to
FAST_DOUBLE_ELEMENTS or
@@ -3786,6 +3788,13 @@
}
}
}
+
+ // Very small array literals that don't have a concrete hint about their
type
+ // from a constant value should default to the slow case to avoid lots of
+ // elements transitions on really small objects.
+ if (has_only_undefined_values && values->length() <= 2) {
+ elements_kind = FAST_ELEMENTS;
+ }
// Simple and shallow arrays can be lazily copied, we transform the
// elements array to a copy-on-write array.
=======================================
--- /branches/bleeding_edge/test/mjsunit/array-natives-elements.js Thu Nov
15 04:19:14 2012
+++ /branches/bleeding_edge/test/mjsunit/array-natives-elements.js Fri Nov
23 05:23:39 2012
@@ -49,7 +49,7 @@
function array_natives_test() {
// Ensure small array literals start in specific element kind mode.
- assertTrue(%HasFastSmiElements([]));
+ assertTrue(%HasFastObjectElements([]));
assertTrue(%HasFastSmiElements([1]));
assertTrue(%HasFastSmiElements([1,2]));
assertTrue(%HasFastDoubleElements([1.1]));
@@ -73,7 +73,7 @@
// Concat
var a1;
a1 = [1,2,3].concat([]);
- assertTrue(%HasFastSmiElements(a1));
+ assertTrue(%HasFastObjectElements(a1));
assertEquals([1,2,3], a1);
a1 = [1,2,3].concat([4,5,6]);
assertTrue(%HasFastSmiElements(a1));
@@ -82,7 +82,7 @@
assertTrue(%HasFastSmiElements(a1));
assertEquals([1,2,3,4,5,6,7,8,9], a1);
a1 = [1.1,2,3].concat([]);
- assertTrue(%HasFastDoubleElements(a1));
+ assertTrue(%HasFastObjectElements(a1));
assertEquals([1.1,2,3], a1);
a1 = [1,2,3].concat([1.1, 2]);
assertTrue(%HasFastDoubleElements(a1));
@@ -173,7 +173,7 @@
a3r = a3.splice(0, 0, 2);
// Commented out since handled in js, which takes the best fit.
// assertTrue(%HasFastDoubleElements(a3r));
- assertTrue(%HasFastSmiElements(a3r));
+ assertTrue(%HasFastObjectElements(a3r));
assertTrue(%HasFastDoubleElements(a3));
assertEquals([], a3r);
assertEquals([2, 1.1, 2, 3], a3);
@@ -187,7 +187,7 @@
a3r = a3.splice(0, 0, 2.1);
// Commented out since handled in js, which takes the best fit.
// assertTrue(%HasFastDoubleElements(a3r));
- assertTrue(%HasFastSmiElements(a3r));
+ assertTrue(%HasFastObjectElements(a3r));
assertTrue(%HasFastDoubleElements(a3));
assertEquals([], a3r);
assertEquals([2.1, 1.1, 2, 3], a3);
@@ -201,7 +201,7 @@
a3r = a3.splice(0, 0, 2.1);
// Commented out since handled in js, which takes the best fit.
// assertTrue(%HasFastDoubleElements(a3r));
- assertTrue(%HasFastSmiElements(a3r));
+ assertTrue(%HasFastObjectElements(a3r));
assertTrue(%HasFastDoubleElements(a3));
assertEquals([], a3r);
assertEquals([2.1, 1, 2, 3], a3);
--
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