X87: Fix uninitialized FixedArray potentially being left behind by ElementsTransitionGenerator::Gen…

src/x87/codegen-x87.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X87
 
 #include "src/codegen.h"
 #include "src/heap/heap.h"
@@ skipping 362 matching lines @@
   __ lea(edi, Operand(ebx, times_2, FixedArray::kHeaderSize));
   __ Allocate(edi, eax, esi, no_reg, &gc_required, TAG_OBJECT);
 
   // eax: destination FixedArray
   // ebx: number of elements
   __ mov(FieldOperand(eax, HeapObject::kMapOffset),
          Immediate(masm->isolate()->factory()->fixed_array_map()));
   __ mov(FieldOperand(eax, FixedArray::kLengthOffset), ebx);
   __ mov(edi, FieldOperand(edx, JSObject::kElementsOffset));
 
+  // Allocating heap numbers in the loop below can fail and cause a jump to
+  // gc_required. We can't leave a partly initialized FixedArray behind,
+  // so pessimistically fill it with holes now.
+  Label initialization_loop, initialization_loop_entry;
+  __ jmp(&initialization_loop_entry, Label::kNear);
+  __ bind(&initialization_loop);
+  __ mov(FieldOperand(eax, ebx, times_2, FixedArray::kHeaderSize),
+         masm->isolate()->factory()->the_hole_value());
+  __ bind(&initialization_loop_entry);
+  __ sub(ebx, Immediate(Smi::FromInt(1)));
+  __ j(not_sign, &initialization_loop);
+
+  __ mov(ebx, FieldOperand(edi, FixedDoubleArray::kLengthOffset));
   __ jmp(&entry);
 
   // ebx: target map
   // edx: receiver
   // Set transitioned map.
   __ bind(&only_change_map);
   __ mov(FieldOperand(edx, HeapObject::kMapOffset), ebx);
   __ RecordWriteField(edx, HeapObject::kMapOffset, ebx, edi, kDontSaveFPRegs,
                       OMIT_REMEMBERED_SET, OMIT_SMI_CHECK);
   __ jmp(&success);
@@ skipping 216 matching lines @@
     Code* stub = GetCodeAgeStub(isolate, age, parity);
     CodePatcher patcher(sequence, young_length);
     patcher.masm()->call(stub->instruction_start(), RelocInfo::NONE32);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X87