Add trivial register hints to the register allocator.

- Add hints for phis, same as first input, and expected registers.
- Make the if instruction accept non-condition instructions.

Change-Id: I34fa68393f0d0c19c68128f017b7a05be556fbe5
diff --git a/compiler/optimizing/instruction_simplifier.h b/compiler/optimizing/instruction_simplifier.h
index b2f3f52..d74b624 100644
--- a/compiler/optimizing/instruction_simplifier.h
+++ b/compiler/optimizing/instruction_simplifier.h
@@ -32,6 +32,7 @@
 
  private:
   virtual void VisitSuspendCheck(HSuspendCheck* check) OVERRIDE;
+  virtual void VisitEqual(HEqual* equal) OVERRIDE;
 };
 
 }  // namespace art