ARM: VIXL32: Do a code cleanup.

This commit is mostly about changing the VIXL-based code generator
to use the new helper functions in more places.

Test: ART_USE_VIXL_ARM_BACKEND=true m test-art-host
Test: ART_USE_VIXL_ARM_BACKEND=true m test-art-target
Change-Id: Ibe35f6a133d5822cc3b7a876cc54590cdaca67fb
diff --git a/compiler/optimizing/intrinsics_arm_vixl.cc b/compiler/optimizing/intrinsics_arm_vixl.cc
index 433dced..d2ca014 100644
--- a/compiler/optimizing/intrinsics_arm_vixl.cc
+++ b/compiler/optimizing/intrinsics_arm_vixl.cc
@@ -1506,7 +1506,7 @@
   SlowPathCodeARMVIXL* slow_path = nullptr;
   HInstruction* code_point = invoke->InputAt(1);
   if (code_point->IsIntConstant()) {
-    if (static_cast<uint32_t>(code_point->AsIntConstant()->GetValue()) >
+    if (static_cast<uint32_t>(Int32ConstantFrom(code_point)) >
         std::numeric_limits<uint16_t>::max()) {
       // Always needs the slow-path. We could directly dispatch to it, but this case should be
       // rare, so for simplicity just put the full slow-path down and branch unconditionally.