Implement code sinking.

Small example of what the optimization does:

Object o = new Object();
if (test) {
  throw new Error(o.toString());
}

will be turned into (note that the first user of 'o'
is the 'new Error' allocation which has 'o' in its
environment):
if (test) {
  Object o = new Obect();
  throw new Error(o.toString());
}

There are other examples in 639-checker-code-sinking.

Ritz individual benchmarks improve on art-jit-cc from
5% (EvaluateComplexFormulas) to 23% (MoveFunctionColumn)
on all platforms.

Test: 639-checker-code-sinking
Test: test-art-host
Test: borg job run
Test: libcore + jdwp

bug:35634932
bug:30933338

Change-Id: Ib99c00c93fe76ffffb17afffb5a0e30a14310652
diff --git a/compiler/optimizing/optimizing_compiler_stats.h b/compiler/optimizing/optimizing_compiler_stats.h
index 203b1ec..172c8f74 100644
--- a/compiler/optimizing/optimizing_compiler_stats.h
+++ b/compiler/optimizing/optimizing_compiler_stats.h
@@ -67,6 +67,7 @@
   kImplicitNullCheckGenerated,
   kExplicitNullCheckGenerated,
   kSimplifyIf,
+  kInstructionSunk,
   kLastStat
 };
 
@@ -147,6 +148,7 @@
       case kImplicitNullCheckGenerated: name = "ImplicitNullCheckGenerated"; break;
       case kExplicitNullCheckGenerated: name = "ExplicitNullCheckGenerated"; break;
       case kSimplifyIf: name = "SimplifyIf"; break;
+      case kInstructionSunk: name = "InstructionSunk"; break;
 
       case kLastStat:
         LOG(FATAL) << "invalid stat "