Improve code sinking near "always throwing" method calls

Rationale:
With simple dex bytecode analysis, the inliner marks methods
that always throw to help subsequent code sinking. This reduces
overhead of non-nullable enforcing calls found in e.g the Kotlin
runtime library (1%-2% improvement on tree microbenchmark, about
5% on Denis' benchmark).

Test: test-art-host test-art-target

Change-Id: I45348f049721476828eb5443738021720d2857c0
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index 4a64285..510eec4 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -1449,7 +1449,10 @@
 }
 
 void InstructionCodeGeneratorX86_64::HandleGoto(HInstruction* got, HBasicBlock* successor) {
-  DCHECK(!successor->IsExitBlock());
+  if (successor->IsExitBlock()) {
+    DCHECK(got->GetPrevious()->AlwaysThrows());
+    return;  // no code needed
+  }
 
   HBasicBlock* block = got->GetBlock();
   HInstruction* previous = got->GetPrevious();