[turbofan] Reserve the StateValueList's size before filling it

Avoid needless resizing of the StateValueList's fields vector by
reserving its (already known) size.

Review-Url: https://codereview.chromium.org/2572683005
Cr-Commit-Position: refs/heads/master@{#41698}

src/compiler/instruction-selector.cc

@@ -555,6 +555,11 @@ size_t InstructionSelector::AddInputsToFrameStateDescriptor(
   DCHECK_EQ(descriptor->stack_count(), StateValuesAccess(stack).size());
 
   StateValueList* values_descriptor = descriptor->GetStateValueDescriptors();
+
+  DCHECK_EQ(values_descriptor->size(), 0u);
+  values_descriptor->ReserveSize(
+      descriptor->GetSize(OutputFrameStateCombine::Ignore()));
+
   entries += AddOperandToStateValueDescriptor(
       values_descriptor, inputs, g, deduplicator, function,
       MachineType::AnyTagged(), FrameStateInputKind::kStackSlot, zone);

src/compiler/instruction.h

@@ -1197,6 +1197,8 @@ class StateValueList {
     ZoneVector<StateValueList*>::iterator nested_iterator;
   };
 
+  void ReserveSize(size_t size) { fields_.reserve(size); }
+
   StateValueList* PushRecursiveField(Zone* zone, size_t id) {
     fields_.push_back(StateValueDescriptor::Recursive(id));
     StateValueList* nested =