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

1 files changed, 1 insertions, 2 deletions

diff --git a/runtime/interpreter/interpreter_switch_impl.cc b/runtime/interpreter/interpreter_switch_impl.cc
index a6349fcf88..582fc9b438 100644
--- a/runtime/interpreter/interpreter_switch_impl.cc
+++ b/runtime/interpreter/interpreter_switch_impl.cc
@@ -477,8 +477,7 @@ JValue ExecuteSwitchImpl(Thread* self, const DexFile::CodeItem* code_item,
         if (LIKELY(c != nullptr)) {
           if (UNLIKELY(c->IsStringClass())) {
             gc::AllocatorType allocator_type = Runtime::Current()->GetHeap()->GetCurrentAllocator();
-            mirror::SetStringCountVisitor visitor(0);
-            obj = String::Alloc<true>(self, 0, allocator_type, visitor);
+            obj = mirror::String::AllocEmptyString<true>(self, allocator_type);
           } else {
             obj = AllocObjectFromCode<do_access_check, true>(
               inst->VRegB_21c(), shadow_frame.GetMethod(), self,