ART: Optimize StringBuilder append pattern.
Recognize appending with StringBuilder and replace the
entire expression with a runtime call that perfoms the
append in a more efficient manner.
For now, require the entire pattern to be in a single block
and be very strict about the StringBuilder environment uses.
Also, do not accept StringBuilder/char[]/Object/float/double
arguments as they throw non-OOME exceptions and/or require a
call from the entrypoint back to a helper function in Java;
these shall be implemented later.
Boot image size for aosp_taimen-userdebug:
- before:
arm/boot*.oat: 19653872
arm64/boot*.oat: 23292784
oat/arm64/services.odex: 22408664
- after:
arm/boot*.oat: 19432184 (-216KiB)
arm64/boot*.oat: 22992488 (-293KiB)
oat/arm64/services.odex: 22376776 (-31KiB)
Note that const-string in compiled boot image methods cannot
throw, but for apps it can and therefore its environment can
prevent the optimization for apps. We could implement either
a simple carve-out for const-string or generic environment
pruning to allow this pattern to be applied more often.
Results for the new StringBuilderAppendBenchmark on taimen:
timeAppendLongStrings: ~700ns -> ~200ns
timeAppendStringAndInt: ~220ns -> ~140ns
timeAppendStrings: ~200ns -> 130ns
Bug: 19575890
Test: 697-checker-string-append
Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Test: aosp_taimen-userdebug boots.
Test: run-gtests.sh
Test: testrunner.py --target --optimizing
Test: vogar --benchmark art/benchmark/stringbuilder-append/src/StringBuilderAppendBenchmark.java
Change-Id: I51789bf299f5219f68ada4c077b6a1d3fe083964
diff --git a/runtime/entrypoints/quick/quick_entrypoints.h b/runtime/entrypoints/quick/quick_entrypoints.h
index 243f7ec..954450f 100644
--- a/runtime/entrypoints/quick/quick_entrypoints.h
+++ b/runtime/entrypoints/quick/quick_entrypoints.h
@@ -34,6 +34,7 @@
class Class;
template<class MirrorType> class CompressedReference;
class Object;
+class String;
} // namespace mirror
class ArtMethod;
@@ -78,6 +79,11 @@
jobject locked, Thread* self)
NO_THREAD_SAFETY_ANALYSIS HOT_ATTR;
+extern "C" mirror::String* artStringBuilderAppend(uint32_t format,
+ const uint32_t* args,
+ Thread* self)
+ REQUIRES_SHARED(Locks::mutator_lock_) HOT_ATTR;
+
extern void ReadBarrierJni(mirror::CompressedReference<mirror::Object>* handle_on_stack,
Thread* self)
NO_THREAD_SAFETY_ANALYSIS HOT_ATTR;