ARM: Fix double use of IP when storing object fields with large offsets.

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"  // NOLINT
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
@@ skipping 1863 matching lines @@
 
 void Assembler::StoreIntoObjectNoBarrierOffset(Register object,
                                                int32_t offset,
                                                Register value,
                                                FieldContent old_content) {
   int32_t ignored = 0;
   if (Address::CanHoldStoreOffset(kWord, offset - kHeapObjectTag, &ignored)) {
     StoreIntoObjectNoBarrier(object, FieldAddress(object, offset), value,
                              old_content);
   } else {
     AddImmediate(IP, object, offset - kHeapObjectTag);

[Florian Schneider, 2015/11/04 20:58:01]

Same issue here?

     StoreIntoObjectNoBarrier(object, Address(IP), value, old_content);
   }
 }
 
 
 void Assembler::StoreIntoObjectNoBarrier(Register object,
                                          const Address& dest,
                                          const Object& value,
                                          FieldContent old_content) {
   ASSERT(value.IsSmi() || value.InVMHeap() ||
          (value.IsOld() && value.IsNotTemporaryScopedHandle()));
   // No store buffer update.
   LoadObject(IP, value);

[Florian Schneider, 2015/11/04 20:58:01]

Would it work to select in DEBUG mode a temp register != object && != IP here in
the same way as we do inside VerifiedWrite?

   VerifiedWrite(dest, IP, old_content);
 }
 
 
 void Assembler::StoreIntoObjectNoBarrierOffset(Register object,
                                                int32_t offset,
                                                const Object& value,
                                                FieldContent old_content) {
   int32_t ignored = 0;
   if (Address::CanHoldStoreOffset(kWord, offset - kHeapObjectTag, &ignored)) {
     StoreIntoObjectNoBarrier(object, FieldAddress(object, offset), value,
                              old_content);
   } else {
-    AddImmediate(IP, object, offset - kHeapObjectTag);
-    StoreIntoObjectNoBarrier(object, Address(IP), value, old_content);
+    ASSERT(object != R9);

[Florian Schneider, 2015/11/04 20:58:01]

Not sure if this is always guaranteed: I think you need to add code to support
object == R9.

+    Push(R9);
+    AddImmediate(R9, object, offset - kHeapObjectTag);
+    StoreIntoObjectNoBarrier(object, Address(R9), value, old_content);
+    Pop(R9);
   }
 }
 
 
 void Assembler::InitializeFieldsNoBarrier(Register object,
                                           Register begin,
                                           Register end,
                                           Register value_even,
                                           Register value_odd) {
   ASSERT(value_odd == value_even + 1);
@@ skipping 1720 matching lines @@
 
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfFpuRegisters));
   return fpu_reg_names[reg];
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM