Ensure inlined static calls perform clinit checks in Optimizing.

Calls to static methods have implicit class initialization
(clinit) checks of the method's declaring class in
Optimizing.  However, when such a static call is inlined,
the implicit clinit check vanishes, possibly leading to an
incorrect behavior.

To ensure that inlining static methods does not change the
behavior of a program, add explicit class initialization
checks (art::HClinitCheck) as well as load class
instructions (art::HLoadClass) as last input of static
calls (art::HInvokeStaticOrDirect) in Optimizing' control
flow graphs, when the declaring class is reachable and not
known to be already initialized.  Then when considering the
inlining of a static method call, proceed only if the method
has no implicit clinit check requirement.

The added explicit clinit checks are already removed by the
art::PrepareForRegisterAllocation visitor.  This CL also
extends this visitor to turn explicit clinit checks from
static invokes into implicit ones after the inlining step,
by removing the added art::HLoadClass nodes mentioned
hereinbefore.

Change-Id: I9ba452b8bd09ae1fdd9a3797ef556e3e7e19c651
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index 23ba339..59f4cc2 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -1966,6 +1966,10 @@
 }
 
 void LocationsBuilderARM64::VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) {
+  // Explicit clinit checks triggered by static invokes must have been
+  // pruned by art::PrepareForRegisterAllocation.
+  DCHECK(!invoke->IsStaticWithExplicitClinitCheck());
+
   IntrinsicLocationsBuilderARM64 intrinsic(GetGraph()->GetArena());
   if (intrinsic.TryDispatch(invoke)) {
     return;
@@ -2016,6 +2020,10 @@
 }
 
 void InstructionCodeGeneratorARM64::VisitInvokeStaticOrDirect(HInvokeStaticOrDirect* invoke) {
+  // Explicit clinit checks triggered by static invokes must have been
+  // pruned by art::PrepareForRegisterAllocation.
+  DCHECK(!invoke->IsStaticWithExplicitClinitCheck());
+
   if (TryGenerateIntrinsicCode(invoke, codegen_)) {
     return;
   }