Avoid use of std::string where we have const char*.

Removing the ClassHelper caused std::string creation for all calls to
Class::GetDescriptor and a significant performance regression. Make the
std::string an out argument so the caller can maintain it and its life time
while allowing GetDescriptor to return the common const char* case.

Don't generate GC maps when compilation is disabled.

Remove other uses of std::string that are occuring on critical paths.
Use the cheaper SkipClass in CompileMethod in CompilerDriver.
Specialize the utf8 as utf16 comparison code for the common shorter byte
encoding.
Force a bit of inlining, remove some UNLIKELYs (they are prone to pessimizing
code), add some LIKELYs.

x86-64 host 1-thread interpret-only of 57 apks:
Before: 29.539s
After: 23.467s

Regular compile:
Before: 1m35.347s
After: 1m20.056s

Bug: 16853450
Change-Id: Ic705ea24784bee24ab80084d06174cbf87d557ad

1 files changed, 1 insertions, 1 deletions

diff --git a/compiler/image_test.cc b/compiler/image_test.cc
index 6b23345..3d119bb 100644
--- a/compiler/image_test.cc
+++ b/compiler/image_test.cc
@@ -123,7 +123,7 @@ TEST_F(ImageTest, WriteRead) {
   }
 
   ASSERT_TRUE(compiler_driver_->GetImageClasses() != NULL);
-  CompilerDriver::DescriptorSet image_classes(*compiler_driver_->GetImageClasses());
+  std::set<std::string> image_classes(*compiler_driver_->GetImageClasses());
 
   // Need to delete the compiler since it has worker threads which are attached to runtime.
   compiler_driver_.reset();