Re-assign registers on ARM so PP and CODE_REG are below R7 (FP on iOS).

runtime/vm/intrinsifier_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/regexp_assembler.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DECLARE_FLAG(bool, interpret_irregexp);
 
 // When entering intrinsics code:
-// R5: IC Data
 // R4: Arguments descriptor
 // LR: Return address
-// The R5, R4 registers can be destroyed only if there is no slow-path, i.e.
+// The R4 register can be destroyed only if there is no slow-path, i.e.
 // if the intrinsified method always executes a return.
 // The FP register should not be modified, because it is used by the profiler.
+// The PP and THR registers (see constants_arm64.h) must be preserved.
 
 #define __ assembler->
 
 
 intptr_t Intrinsifier::ParameterSlotFromSp() { return -1; }
 
 
 // Intrinsify only for Smi value and index. Non-smi values need a store buffer
 // update. Array length is always a Smi.
 void Intrinsifier::ObjectArraySetIndexed(Assembler* assembler) {
@@ skipping 2046 matching lines @@
 
 void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
   __ LoadIsolate(R0);
   __ ldr(R0, Address(R0, Isolate::current_tag_offset()));
   __ ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64