Implement leaf runtime call stub on ARM and corresponding call redirection

runtime/vm/assembler_arm.cc

 // Copyright (c) 2013, 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"
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/simulator.h"
 #include "vm/runtime_entry.h"
@@ skipping 1380 matching lines @@
 }
 
 
 void Assembler::Rrx(Register rd, Register rm, Condition cond) {
   mov(rd, ShifterOperand(rm, ROR, 0), cond);
 }
 
 
 void Assembler::Branch(const ExternalLabel* label, Condition cond) {
   LoadImmediate(IP, label->address(), cond);  // Address is never patched.
-  mov(PC, ShifterOperand(IP), cond);
+  bx(IP, cond);
+}
+
+
+void Assembler::BranchPatchable(const ExternalLabel* label) {
+  // Use a fixed size code sequence, since a function prologue may be patched
+  // with this branch sequence.
+  // Contrarily to BranchLinkPatchable, BranchPatchable requires an instruction
+  // cache flush upon patching.
+  movw(IP, Utils::Low16Bits(label->address()));
+  movt(IP, Utils::High16Bits(label->address()));
+  bx(IP);
 }
 
 
 void Assembler::BranchLink(const ExternalLabel* label) {
   LoadImmediate(IP, label->address());  // Target address is never patched.
   blx(IP);  // Use blx instruction so that the return branch prediction works.
 }
 
 
 void Assembler::BranchLinkPatchable(const ExternalLabel* label) {
@@ skipping 540 matching lines @@
   // Do not reuse an existing entry, since each reference may be patched
   // independently.
   object_pool_.Add(smi);
   return object_pool_.Length() - 1;
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM