commit 3aaa37bba53d6df0265793de48b4b0b57327e57a
author jessicahandojo <jessicahandojo@google.com> Fri Jul 29 14:46:37 2016 -0700
committer jessicahandojo <jessicahandojo@google.com> Tue Aug 23 15:12:26 2016 -0700
tree ce795803f0f10003eb3d96d9348da620937675b3
parent 792c98bb773c8c2390f9cbf774f85be9d9a75332

creating workflow for mirror::String compression

All-ASCII String characters are stored in 8-bit blocks
instead of 16-bit. The compression has not taken place, but all
workflow are in the code already (changing kUseStringCompression in
string.h file to TRUE will enable the feature)

Notes: Feature works on interpreter only without optimizing

Test art: m ART_TEST_INTERPRETER=true ART_TEST_OPTIMIZING=false
          test-art-host

Also tested with String tests from libcore/:
1. libcore.java.lang.StringTest
2. libcore.java.lang.StringBufferTest
3. libcore.java.lang.StringBuilderTest
4. libcore.java.lang.OldStringTest
5. libcore.java.lang.OldStringBufferTest

Memory improvement is 33% (from 6.03% to 4.03%, total String memory
from all apps per total memory of all apps) measured on Angler
with Hprof tools

Bug: 31040547
Change-Id: I9cc92c265ebf1305fc06b5fc33efd83797660cce

runtime/debugger.cc

diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index 2a5198b..cbdf3dc 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -1286,8 +1286,7 @@
   if (c->IsStringClass()) {
     // Special case for java.lang.String.
     gc::AllocatorType allocator_type = Runtime::Current()->GetHeap()->GetCurrentAllocator();
-    mirror::SetStringCountVisitor visitor(0);
-    new_object = mirror::String::Alloc<true>(self, 0, allocator_type, visitor);
+    new_object = mirror::String::AllocEmptyString<true>(self, allocator_type);
   } else {
     new_object = c->AllocObject(self);
   }
@@ -4327,10 +4326,16 @@
     Handle<mirror::String> name(hs.NewHandle(t->GetThreadName(soa)));
     size_t char_count = (name.Get() != nullptr) ? name->GetLength() : 0;
     const jchar* chars = (name.Get() != nullptr) ? name->GetValue() : nullptr;
+    bool is_compressed = (name.Get() != nullptr) ? name->IsCompressed() : false;
 
     std::vector<uint8_t> bytes;
     JDWP::Append4BE(bytes, t->GetThreadId());
-    JDWP::AppendUtf16BE(bytes, chars, char_count);
+    if (is_compressed) {
+      const uint8_t* chars_compressed = name->GetValueCompressed();
+      JDWP::AppendUtf16CompressedBE(bytes, chars_compressed, char_count);
+    } else {
+      JDWP::AppendUtf16BE(bytes, chars, char_count);
+    }
     CHECK_EQ(bytes.size(), char_count*2 + sizeof(uint32_t)*2);
     Dbg::DdmSendChunk(type, bytes);
   }