Reviewers: Benedikt Meurer,
Description:
Flatten cons string for single character substrings.
For substrings of non-flat cons strings, we bail out
to runtime. For single character substrings, we forget
to flatten it. This causes successive bailouts.
[email protected]
BUG=323041
Please review this at https://codereview.chromium.org/88143002/
Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index
f28c9260b9d8ebc211381ed971db3bbfaad88977..cf9d6c709ee489f0658196d3244c96c12e822c1c
100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -3968,7 +3968,12 @@ MaybeObject* Heap::AllocateSubString(String* buffer,
int length = end - start;
if (length <= 0) {
return empty_string();
- } else if (length == 1) {
+ }
+
+ // Make an attempt to flatten the buffer to reduce access time.
+ buffer = buffer->TryFlattenGetString();
+
+ if (length == 1) {
return LookupSingleCharacterStringFromCode(buffer->Get(start));
} else if (length == 2) {
// Optimization for 2-byte strings often used as keys in a
decompression
@@ -3979,9 +3984,6 @@ MaybeObject* Heap::AllocateSubString(String* buffer,
return MakeOrFindTwoCharacterString(this, c1, c2);
}
- // Make an attempt to flatten the buffer to reduce access time.
- buffer = buffer->TryFlattenGetString();
-
if (!FLAG_string_slices ||
!buffer->IsFlat() ||
length < SlicedString::kMinLength ||
@@ -4981,7 +4983,7 @@ MaybeObject*
Heap::ReinitializeJSGlobalProxy(JSFunction* constructor,
MaybeObject* Heap::AllocateStringFromOneByte(Vector<const uint8_t> string,
- PretenureFlag pretenure) {
+ PretenureFlag pretenure) {
int length = string.length();
if (length == 1) {
return Heap::LookupSingleCharacterStringFromCode(string[0]);
Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index
67e5e9e3dfaf84a7d2c2c57ab51c41cc7a408105..76ca766055af5fcb2fdee4d30b33da23e938328a
100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -4463,10 +4463,6 @@ RUNTIME_FUNCTION(MaybeObject*, Runtime_SubString) {
RUNTIME_ASSERT(start >= 0);
RUNTIME_ASSERT(end <= value->length());
isolate->counters()->sub_string_runtime()->Increment();
- if (end - start == 1) {
- return isolate->heap()->LookupSingleCharacterStringFromCode(
- value->Get(start));
- }
return value->SubString(start, end);
}
--
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