Avoid the compiler reloading the base register for every store.

Removes 3 unnecessary loads in a very small leaf function.
Instead of
2c:   48 8b 47 20             mov    0x20(%rdi),%rax
30:   f2 0f 11 00             movsd  %xmm0,(%rax)
34:   48 8b 47 20             mov    0x20(%rdi),%rax
38:   48 c7 40 08 00 00 00    movq   $0x0,0x8(%rax)
3f:   00
40:   48 8b 47 20             mov    0x20(%rdi),%rax
44:   48 c7 40 10 00 00 00    movq   $0x0,0x10(%rax)
4b:   00
4c:   48 8b 47 20             mov    0x20(%rdi),%rax
50:   48 89 48 18             mov    %rcx,0x18(%rax)
54:   c3                      retq

We get
23c:       48 8b 47 20             mov    0x20(%rdi),%rax
240:       f2 0f 11 00             movsd  %xmm0,(%rax)
244:       48 c7 40 08 00 00 00    movq   $0x0,0x8(%rax)
24b:       00
24c:       48 c7 40 10 00 00 00    movq   $0x0,0x10(%rax)
253:       00
254:       48 89 48 18             mov    %rcx,0x18(%rax)
258:       c3                      retq

2 files changed, 27 insertions, 20 deletions

diff --git a/searchlib/src/vespa/searchlib/features/attributefeature.cpp b/searchlib/src/vespa/searchlib/features/attributefeature.cpp
index 4f45b3090f0..45ecac90e9d 100644
--- a/searchlib/src/vespa/searchlib/features/attributefeature.cpp
+++ b/searchlib/src/vespa/searchlib/features/attributefeature.cpp
@@ -93,11 +93,11 @@ considerUndefined<ConstCharPtr>(ConstCharPtr value, BasicType::Type )
     return search::features::util::getAsFeature(value);
 }
 
-
 }
 
 
 namespace search::features {
+namespace {
 
 /**
  * Implements the executor for fetching values from a single or array attribute vector
@@ -201,12 +201,13 @@ SingleAttributeExecutor<T>::execute(uint32_t docId)
 {
     typename T::LoadedValueType v = _attribute.getFast(docId);
     // value
-    outputs().set_number(0, __builtin_expect(attribute::isUndefined(v), false)
-                         ? attribute::getUndefined<feature_t>()
-                         : util::getAsFeature(v));
-    outputs().set_number(1, 0.0f);  // weight
-    outputs().set_number(2, 0.0f);  // contains
-    outputs().set_number(3, 1.0f);  // count
+    fef::NumberOrObject * o = outputs().get_raw(0);
+    o[0].as_number = __builtin_expect(attribute::isUndefined(v), false)
+                     ? attribute::getUndefined<feature_t>()
+                     : util::getAsFeature(v);
+    o[1].as_number = 0;  // weight
+    o[2].as_number = 0;  // contains
+    o[3].as_number = 1;  // contains
 }
 
 template <typename T>
@@ -216,20 +217,21 @@ MultiAttributeExecutor<T>::execute(uint32_t docId)
     const multivalue::Value<typename T::BaseType> * values = nullptr;
     uint32_t numValues = _attribute.getRawValues(docId, values);
 
-    outputs().set_number(0, __builtin_expect(_idx < numValues, true)
-                         ? values[_idx].value() : 0.0f);
-    outputs().set_number(1, 0.0f);  // weight
-    outputs().set_number(2, 0.0f);  // contains
-    outputs().set_number(3, 0.0f);  // count
+    fef::NumberOrObject * o = outputs().get_raw(0);
+    o[0].as_number = __builtin_expect(_idx < numValues, true) ? values[_idx].value() : 0;
+    o[1].as_number = 0;  // weight
+    o[2].as_number = 0;  // contains
+    o[3].as_number = 0;  // count
 }
 
 void
 CountOnlyAttributeExecutor::execute(uint32_t docId)
 {
-    outputs().set_number(0, 0.0f);  // value
-    outputs().set_number(1, 0.0f);  // weight
-    outputs().set_number(2, 0.0f);  // contains
-    outputs().set_number(3, _attribute.getValueCount(docId)); // count
+    fef::NumberOrObject * o = outputs().get_raw(0);
+    o[0].as_number = 0;  // value
+    o[1].as_number = 0;  // weight
+    o[2].as_number = 0;  // contains
+    o[3].as_number = _attribute.getValueCount(docId); // count
 }
 
 template <typename T>
@@ -253,10 +255,11 @@ AttributeExecutor<T>::execute(uint32_t docId)
     if (_idx < _buffer.size()) {
         value = considerUndefined(_buffer[_idx], _attrType);
     }
-    outputs().set_number(0, value);         // value
-    outputs().set_number(1, 0.0f);          // weight
-    outputs().set_number(2, 0.0f);          // contains
-    outputs().set_number(3, _defaultCount); // count
+    fef::NumberOrObject * o = outputs().get_raw(0);
+    o[0].as_number = value;  // value
+    o[1].as_number = 0;  // weight
+    o[2].as_number = 0;  // contains
+    o[3].as_number = _defaultCount; // count
 }
 
 
@@ -298,6 +301,7 @@ WeightedSetAttributeExecutor<BT, T>::execute(uint32_t docId)
     outputs().set_number(3, count);    // count
 }
 
+}
 
 AttributeBlueprint::AttributeBlueprint() :
     fef::Blueprint("attribute"),
diff --git a/searchlib/src/vespa/searchlib/fef/featureexecutor.h b/searchlib/src/vespa/searchlib/fef/featureexecutor.h
index dc8a4ba6075..fd36fbe5a20 100644
--- a/searchlib/src/vespa/searchlib/fef/featureexecutor.h
+++ b/searchlib/src/vespa/searchlib/fef/featureexecutor.h
@@ -83,6 +83,9 @@ public:
         const NumberOrObject *get_raw(size_t idx) const {
             return &_outputs[idx];
         }
+        NumberOrObject *get_raw(size_t idx) {
+            return &_outputs[idx];
+        }
         size_t size() const { return _outputs.size(); }
     };