Reviewers: jarin,
Description:
[turbofan] Specify better type for FixedArray::length field.
This avoids redundant smi checks when using the length of a FixedArray,
which is always a positve smi.
[email protected]
Please review this at https://codereview.chromium.org/1162163003/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+6, -1 lines):
M src/compiler/access-builder.cc
Index: src/compiler/access-builder.cc
diff --git a/src/compiler/access-builder.cc b/src/compiler/access-builder.cc
index
c728154d7f4e2bb263f6bdf3d9fc64ae55f97bfe..b9986f28fc3ef015b11bce76f9a2cc925fecb200
100644
--- a/src/compiler/access-builder.cc
+++ b/src/compiler/access-builder.cc
@@ -46,8 +46,13 @@ FieldAccess
AccessBuilder::ForJSArrayBufferBackingStore() {
// static
FieldAccess AccessBuilder::ForFixedArrayLength() {
+ // TODO(turbofan): 2^30 is a valid upper limit for the FixedArray::length
+ // field, although it's not the best. If we had a Zone we could create an
+ // appropriate range type instead.
+ STATIC_ASSERT(FixedArray::kMaxLength <= 1 << 30);
return {kTaggedBase, FixedArray::kLengthOffset, MaybeHandle<Name>(),
- Type::TaggedSigned(), kMachAnyTagged};
+ Type::Intersect(Type::Unsigned30(), Type::TaggedSigned()),
+ kMachAnyTagged};
}
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