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[turbofan] Compute proper type for globals with "constant type".

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For property cells with cell type kConstantType, we can compute an
appropriate JavaScript type based on the current value of that cell.
Numbers cannot use Type::Of here, because the type might be too precise,
so we handle smi and heap number specially.

R=jarin@chromium.org
BUG=v8:4470
LOG=n

Review URL: https://codereview.chromium.org/1400483002

Cr-Commit-Position: refs/heads/master@{#31171}
This commit is contained in:
bmeurer 2015-10-08 01:58:57 -07:00 committed by Commit bot
parent 948c4b40d9
commit fd4e0dc2ce
1 changed files with 10 additions and 11 deletions
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21
src/compiler/js-global-specialization.cc
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@ -145,17 +145,16 @@ Reduction JSGlobalSpecialization::ReduceLoadFromPropertyCell(
if (property_details.cell_type() == PropertyCellType::kConstantType &&
(flags() & kDeoptimizationEnabled)) {
dependencies()->AssumePropertyCell(property_cell);
Type* property_cell_value_type = Type::Any();
switch (property_cell->GetConstantType()) {
case PropertyCellConstantType::kSmi:
property_cell_value_type = Type::Intersect(
Type::SignedSmall(), Type::TaggedSigned(), graph()->zone());
break;
case PropertyCellConstantType::kStableMap: {
// TODO(bmeurer): Determine type based on the map's instance type.
property_cell_value_type = Type::TaggedPointer();
break;
}
// Compute proper type based on the current value in the cell.
Type* property_cell_value_type;
if (property_cell_value->IsSmi()) {
property_cell_value_type = Type::Intersect(
Type::SignedSmall(), Type::TaggedSigned(), graph()->zone());
} else if (property_cell_value->IsNumber()) {
property_cell_value_type = Type::Intersect(
Type::Number(), Type::TaggedPointer(), graph()->zone());
} else {
property_cell_value_type = Type::Of(property_cell_value, graph()->zone());
}
Node* value = effect = graph()->NewNode(
simplified()->LoadField(