AuroraMiddleware/v8
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[turbofan] Eliminate empty string addition.

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For additions like a+'' or ''+a where we have String feedback on the
JSAdd, we can drop the concatenation and just check that a is a valid
String already (via CheckString).

BUG=v8:6259
R=petermarshall@chromium.org

Review-Url: https://codereview.chromium.org/2894563002
Cr-Commit-Position: refs/heads/master@{#45395}
This commit is contained in:
bmeurer 2017-05-18 04:31:50 -07:00 committed by Commit bot
parent de4a4095cf
commit cd1325a890
2 changed files with 25 additions and 7 deletions
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31
src/compiler/js-typed-lowering.cc
View File

@ -488,13 +488,13 @@ JSTypedLowering::JSTypedLowering(Editor* editor,
dependencies_(dependencies),
flags_(flags),
jsgraph_(jsgraph),
pointer_comparable_type_(Type::Union(
Type::Oddball(),
Type::Union(
Type::SymbolOrReceiver(),
Type::HeapConstant(factory()->empty_string(), graph()->zone()),
graph()->zone()),
graph()->zone())),
empty_string_type_(
Type::HeapConstant(factory()->empty_string(), graph()->zone())),
pointer_comparable_type_(
Type::Union(Type::Oddball(),
Type::Union(Type::SymbolOrReceiver(), empty_string_type_,
graph()->zone()),
graph()->zone())),
type_cache_(TypeCache::Get()) {
for (size_t k = 0; k < arraysize(shifted_int32_ranges_); ++k) {
double min = kMinInt / (1 << k);
@ -535,6 +535,23 @@ Reduction JSTypedLowering::ReduceJSAdd(Node* node) {
if (r.ShouldCreateConsString()) {
return ReduceCreateConsString(node);
}
// Eliminate useless concatenation of empty string.
if ((flags() & kDeoptimizationEnabled) &&
BinaryOperationHintOf(node->op()) == BinaryOperationHint::kString) {
Node* effect = NodeProperties::GetEffectInput(node);
Node* control = NodeProperties::GetControlInput(node);
if (r.LeftInputIs(empty_string_type_)) {
Node* value = effect = graph()->NewNode(simplified()->CheckString(),
r.right(), effect, control);
ReplaceWithValue(node, value, effect, control);
return Replace(value);
} else if (r.RightInputIs(empty_string_type_)) {
Node* value = effect = graph()->NewNode(simplified()->CheckString(),
r.left(), effect, control);
ReplaceWithValue(node, value, effect, control);
return Replace(value);
}
}
StringAddFlags flags = STRING_ADD_CHECK_NONE;
if (!r.LeftInputIs(Type::String())) {
flags = STRING_ADD_CONVERT_LEFT;

1
src/compiler/js-typed-lowering.h
View File

@ -105,6 +105,7 @@ class V8_EXPORT_PRIVATE JSTypedLowering final
CompilationDependencies* dependencies_;
Flags flags_;
JSGraph* jsgraph_;
Type* empty_string_type_;
Type* shifted_int32_ranges_[4];
Type* pointer_comparable_type_;
TypeCache const& type_cache_;