Reviewers: Yang,
Message:
ptal - maybe this fixes this regression, but it's really hard to tell
locally,
so it's mostly a guess
Description:
add fast path for hashing small cons strings
BUG=437280
Please review this at https://codereview.chromium.org/769453002/
Base URL: https://chromium.googlesource.com/v8/v8.git@master
Affected files (+14, -3 lines):
M src/objects.cc
M src/objects-inl.h
Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index
98d96a8f28ac0747517e1b407753ed869a817ba0..efe7c363b3d6acd0c092a3d23dcaeea293fbfb3a
100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -6825,9 +6825,8 @@ uint32_t IteratingStringHasher::Hash(String* string,
uint32_t seed) {
// Nothing to do.
if (hasher.has_trivial_hash()) return hasher.GetHashField();
ConsString* cons_string = String::VisitFlat(&hasher, string);
- if (cons_string != nullptr) {
- hasher.VisitConsString(cons_string);
- }
+ if (cons_string == nullptr) return hasher.GetHashField();
+ hasher.VisitConsString(cons_string);
return hasher.GetHashField();
}
Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index
15fdce65d98a63d8a89c1edbc474e818ec634ee3..89451524076a19e5a7356515e00db8c9e2304bb7
100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9298,6 +9298,18 @@ uint32_t StringHasher::ComputeUtf8Hash(Vector<const
char> chars,
void IteratingStringHasher::VisitConsString(ConsString* cons_string) {
+ // Run small ConsStrings through ConsStringIterator.
+ if (cons_string->length() < 64) {
+ ConsStringIterator iter(cons_string);
+ int offset;
+ String* string;
+ while (nullptr != (string = iter.Next(&offset))) {
+ DCHECK_EQ(0, offset);
+ String::VisitFlat(this, string, 0);
+ }
+ return;
+ }
+ // Slow case.
const int max_length = String::kMaxHashCalcLength;
int length = std::min(cons_string->length(), max_length);
if (cons_string->HasOnlyOneByteChars()) {
--
--
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