Save a few register moves in function prolog on arm64 by using the same pattern

runtime/vm/assembler_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"  // NOLINT
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
@@ skipping 284 matching lines @@
       imm_s_fixed >>= 1;
       continue;
     }
 
     // 6. Otherwise, the value can't be encoded.
     return false;
   }
 }
 
 
-void Assembler::LoadPoolPointer() {
+void Assembler::LoadPoolPointer(Register pp) {
   const intptr_t object_pool_pc_dist =
     Instructions::HeaderSize() - Instructions::object_pool_offset() +
     CodeSize();
   // PP <- Read(PC - object_pool_pc_dist).
-  ldr(PP, Address::PC(-object_pool_pc_dist));
+  ldr(pp, Address::PC(-object_pool_pc_dist));
 
   // When in the PP register, the pool pointer is untagged. When we
   // push it on the stack with TagAndPushPP it is tagged again. PopAndUntagPP
   // then untags when restoring from the stack. This will make loading from the
   // object pool only one instruction for the first 4096 entries. Otherwise,
   // because the offset wouldn't be aligned, it would be only one instruction
   // for the first 64 entries.
-  sub(PP, PP, Operand(kHeapObjectTag));
-  set_constant_pool_allowed(true);
+  sub(pp, pp, Operand(kHeapObjectTag));
+  set_constant_pool_allowed(pp == PP);
 }
 
 
 void Assembler::LoadWordFromPoolOffset(Register dst, uint32_t offset) {
   ASSERT(constant_pool_allowed());
   ASSERT(dst != PP);
   Operand op;
   const uint32_t upper20 = offset & 0xfffff000;
   if (Address::CanHoldOffset(offset)) {
     ldr(dst, Address(PP, offset));
@@ skipping 90 matching lines @@
         is_unique ? object_pool_wrapper_.AddObject(object)
                   : object_pool_wrapper_.FindObject(object));
     LoadWordFromPoolOffset(dst, offset);
   } else {
     ASSERT(object.IsSmi() || object.InVMHeap());
     LoadDecodableImmediate(dst, reinterpret_cast<int64_t>(object.raw()));
   }
 }
 
 
+void Assembler::LoadFunctionFromCalleePool(Register dst,
+                                           const Function& function,
+                                           Register new_pp) {
+  ASSERT(!constant_pool_allowed());
+  ASSERT(new_pp != PP);
+  const int32_t offset =
+      ObjectPool::element_offset(object_pool_wrapper_.FindObject(function));
+  ASSERT(Address::CanHoldOffset(offset));
+  ldr(dst, Address(new_pp, offset));
+}
+
+
 void Assembler::LoadObject(Register dst, const Object& object) {
   LoadObjectHelper(dst, object, false);
 }
 
 
 void Assembler::LoadUniqueObject(Register dst, const Object& object) {
   LoadObjectHelper(dst, object, true);
 }
 
 
@@ skipping 996 matching lines @@
     add(base, array, Operand(index, LSL, shift));
   }
   const OperandSize size = Address::OperandSizeFor(cid);
   ASSERT(Address::CanHoldOffset(offset, Address::Offset, size));
   return Address(base, offset, Address::Offset, size);
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64