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 1706 matching lines @@
     Operand shadow(GetVerifiedMemoryShadow());
     add(base, base, shadow, cond);
     strd(value_even, value_odd, base, offset, cond);
     sub(base, base, shadow, cond);
   }
   strd(value_even, value_odd, base, offset, cond);
 }
 
 
 Register UseRegister(Register reg, RegList* used) {
+  ASSERT(reg != THR);
   ASSERT(reg != SP);
+  ASSERT(reg != FP);
   ASSERT(reg != PC);
   ASSERT((*used & (1 << reg)) == 0);
   *used |= (1 << reg);
   return reg;
 }
 
 
 Register AllocateRegister(RegList* used) {
   const RegList free = ~*used;
   return (free == 0) ?
       kNoRegister :
       UseRegister(static_cast<Register>(Utils::CountTrailingZeros(free)), used);
 }
 
 
-void Assembler::VerifiedWrite(const Address& address,
+void Assembler::VerifiedWrite(Register object,
+                              const Address& address,
                               Register new_value,
                               FieldContent old_content) {
 #if defined(DEBUG)
   ASSERT(address.mode() == Address::Offset ||
          address.mode() == Address::NegOffset);
   // Allocate temporary registers (and check for register collisions).
   RegList used = 0;
   UseRegister(new_value, &used);
   Register base = UseRegister(address.rn(), &used);
+  if ((object != base) && (object != kNoRegister)) {

[Florian Schneider, 2015/11/05 01:50:35]

I guess not checking (object != base) would be ok, too. Like below, we don't
check (adress.rm() != base). I'm ok either way.

+    UseRegister(object, &used);
+  }
   if (address.rm() != kNoRegister) {
     UseRegister(address.rm(), &used);
   }
   Register old_value = AllocateRegister(&used);
   Register temp = AllocateRegister(&used);
   PushList(used);
   ldr(old_value, address);
   // First check that 'old_value' contains 'old_content'.
   // Smi test.
   tst(old_value, Operand(kHeapObjectTag));
@@ skipping 48 matching lines @@
   str(new_value, address);
 #endif  // DEBUG
 }
 
 
 void Assembler::StoreIntoObject(Register object,
                                 const Address& dest,
                                 Register value,
                                 bool can_value_be_smi) {
   ASSERT(object != value);
-  VerifiedWrite(dest, value, kHeapObjectOrSmi);
+  VerifiedWrite(object, dest, value, kHeapObjectOrSmi);
   Label done;
   if (can_value_be_smi) {
     StoreIntoObjectFilter(object, value, &done);
   } else {
     StoreIntoObjectFilterNoSmi(object, value, &done);
   }
   // A store buffer update is required.
   RegList regs = (1 << CODE_REG) | (1 << LR);
   if (value != R0) {
     regs |= (1 << R0);  // Preserve R0.
@@ skipping 22 matching lines @@
     AddImmediate(IP, object, offset - kHeapObjectTag);
     StoreIntoObject(object, Address(IP), value, can_value_be_smi);
   }
 }
 
 
 void Assembler::StoreIntoObjectNoBarrier(Register object,
                                          const Address& dest,
                                          Register value,
                                          FieldContent old_content) {
-  VerifiedWrite(dest, value, old_content);
+  VerifiedWrite(object, dest, value, old_content);
 #if defined(DEBUG)
   Label done;
   StoreIntoObjectFilter(object, value, &done);
   Stop("Store buffer update is required");
   Bind(&done);
 #endif  // defined(DEBUG)
   // No store buffer update.
 }
 
 
@@ skipping 13 matching lines @@
 
 
 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);
-  VerifiedWrite(dest, IP, old_content);
+  VerifiedWrite(object, 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);
+    Register base = object == R9 ? R8 : R9;
+    Push(base);
+    AddImmediate(base, object, offset - kHeapObjectTag);
+    StoreIntoObjectNoBarrier(object, Address(base), value, old_content);
+    Pop(base);
   }
 }
 
 
 void Assembler::InitializeFieldsNoBarrier(Register object,
                                           Register begin,
                                           Register end,
                                           Register value_even,
                                           Register value_odd) {
   ASSERT(value_odd == value_even + 1);
@@ skipping 43 matching lines @@
 
 
 void Assembler::StoreIntoSmiField(const Address& dest, Register value) {
 #if defined(DEBUG)
   Label done;
   tst(value, Operand(kHeapObjectTag));
   b(&done, EQ);
   Stop("New value must be Smi.");
   Bind(&done);
 #endif  // defined(DEBUG)
-  VerifiedWrite(dest, value, kOnlySmi);
+  VerifiedWrite(kNoRegister, dest, value, kOnlySmi);
 }
 
 
 void Assembler::LoadClassId(Register result, Register object, Condition cond) {
   ASSERT(RawObject::kClassIdTagPos == 16);
   ASSERT(RawObject::kClassIdTagSize == 16);
   const intptr_t class_id_offset = Object::tags_offset() +
       RawObject::kClassIdTagPos / kBitsPerByte;
   ldrh(result, FieldAddress(object, class_id_offset), cond);
 }
@@ skipping 1656 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