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/string_builder_append.h b/runtime/string_builder_append.h
new file mode 100644
index 0000000..fee6419
--- /dev/null
+++ b/runtime/string_builder_append.h
@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2019 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_STRING_BUILDER_APPEND_H_
+#define ART_RUNTIME_STRING_BUILDER_APPEND_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "base/bit_utils.h"
+#include "base/locks.h"
+#include "obj_ptr.h"
+
+namespace art {
+
+class Thread;
+
+namespace mirror {
+class String;
+} // namespace mirror
+
+class StringBuilderAppend {
+ public:
+ enum class Argument : uint8_t {
+ kEnd = 0u,
+ kObject,
+ kStringBuilder,
+ kString,
+ kCharArray,
+ kBoolean,
+ kChar,
+ kInt,
+ kLong,
+ kFloat,
+ kDouble,
+ kLast = kDouble
+ };
+
+ static constexpr size_t kBitsPerArg =
+ MinimumBitsToStore(static_cast<size_t>(Argument::kLast));
+ static constexpr size_t kMaxArgs = BitSizeOf<uint32_t>() / kBitsPerArg;
+ static_assert(kMaxArgs * kBitsPerArg == BitSizeOf<uint32_t>(), "Expecting no extra bits.");
+ static constexpr uint32_t kArgMask = MaxInt<uint32_t>(kBitsPerArg);
+
+ static ObjPtr<mirror::String> AppendF(uint32_t format, const uint32_t* args, Thread* self)
+ REQUIRES_SHARED(Locks::mutator_lock_);
+
+ private:
+ class Builder;
+};
+
+} // namespace art
+
+#endif // ART_RUNTIME_STRING_BUILDER_APPEND_H_