MIPS: Fix uninitialized FixedArray potentially being left behind by ElementsTransitionGenerator::Ge…

src/mips/codegen-mips.cc

Index: src/mips/codegen-mips.cc
diff --git a/src/mips/codegen-mips.cc b/src/mips/codegen-mips.cc
index 0ecac19b49219ffa2b06d1604b04746fe2b14fe3..599aace2ee67a2879b39d62f9f3eee91f3e48c7b 100644
--- a/src/mips/codegen-mips.cc
+++ b/src/mips/codegen-mips.cc
@@ -896,9 +896,23 @@ void ElementsTransitionGenerator::GenerateDoubleToObject(
         FixedDoubleArray::kHeaderSize - kHeapObjectTag
         + Register::kExponentOffset));
   __ Addu(dst_elements, array, Operand(FixedArray::kHeaderSize));
-  __ Addu(array, array, Operand(kHeapObjectTag));
   __ sll(dst_end, dst_end, 1);
   __ Addu(dst_end, dst_elements, dst_end);
+
+  // 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;
+  __ LoadRoot(scratch, Heap::kTheHoleValueRootIndex);
+  __ Branch(&initialization_loop_entry);
+  __ bind(&initialization_loop);
+  __ sw(scratch, MemOperand(dst_elements));
+  __ Addu(dst_elements, dst_elements, Operand(kPointerSize));
+  __ bind(&initialization_loop_entry);
+  __ Branch(&initialization_loop, lt, dst_elements, Operand(dst_end));
+
+  __ Addu(dst_elements, array, Operand(FixedArray::kHeaderSize));
+  __ Addu(array, array, Operand(kHeapObjectTag));
   __ LoadRoot(heap_number_map, Heap::kHeapNumberMapRootIndex);
   // Using offsetted addresses.
   // dst_elements: begin of destination FixedArray element fields, not tagged