[compiler] Read the FixedDoubleArray value from the Ref only once

When reading the FixedDoubleArray value and representation, we are
reading the same value but bitcasting it diffrently. In this vein, we
can read it only once and ask whether it is the hole or not.

Bug: v8:7790
Change-Id: I0d7b29ce037b9abb55c5a1332c7e6d06887905e1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2428587Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70119}

src/compiler/heap-refs.h

@@ -10,6 +10,7 @@
 #include "src/objects/elements-kind.h"
 #include "src/objects/feedback-vector.h"
 #include "src/objects/instance-type.h"
+#include "src/utils/boxed-float.h"
 
 namespace v8 {
 class CFunctionInfo;
@@ -719,8 +720,7 @@ class FixedDoubleArrayRef : public FixedArrayBaseRef {
 
   Handle<FixedDoubleArray> object() const;
 
-  double get_scalar(int i) const;
-  bool is_the_hole(int i) const;
+  Float64 get(int i) const;
 };
 
 class BytecodeArrayRef : public FixedArrayBaseRef {

src/compiler/js-create-lowering.cc

@@ -1770,10 +1770,11 @@ Node* JSCreateLowering::AllocateFastLiteralElements(Node* effect, Node* control,
   if (elements_map.instance_type() == FIXED_DOUBLE_ARRAY_TYPE) {
     FixedDoubleArrayRef elements = boilerplate_elements.AsFixedDoubleArray();
     for (int i = 0; i < elements_length; ++i) {
-      if (elements.is_the_hole(i)) {
+      Float64 value = elements.get(i);
+      if (value.is_hole_nan()) {
         elements_values[i] = jsgraph()->TheHoleConstant();
       } else {
-        elements_values[i] = jsgraph()->Constant(elements.get_scalar(i));
+        elements_values[i] = jsgraph()->Constant(value.get_scalar());
       }
     }
   } else {

src/compiler/js-heap-broker.cc

@@ -34,7 +34,6 @@
 #include "src/objects/objects-inl.h"
 #include "src/objects/template-objects-inl.h"
 #include "src/objects/templates.h"
-#include "src/utils/boxed-float.h"
 #include "src/utils/utils.h"
 
 namespace v8 {
@@ -3198,24 +3197,13 @@ ObjectRef FixedArrayRef::get(int i) const {
   return ObjectRef(broker(), data()->AsFixedArray()->Get(i));
 }
 
-bool FixedDoubleArrayRef::is_the_hole(int i) const {
+Float64 FixedDoubleArrayRef::get(int i) const {
   if (data_->should_access_heap()) {
     AllowHandleDereferenceIfNeeded allow_handle_dereference(data()->kind(),
                                                             broker()->mode());
-    return object()->is_the_hole(i);
+    return Float64::FromBits(object()->get_representation(i));
   } else {
-    return data()->AsFixedDoubleArray()->Get(i).is_hole_nan();
-  }
-}
-
-double FixedDoubleArrayRef::get_scalar(int i) const {
-  if (data_->should_access_heap()) {
-    AllowHandleDereferenceIfNeeded allow_handle_dereference(data()->kind(),
-                                                            broker()->mode());
-    return object()->get_scalar(i);
-  } else {
-    CHECK(!data()->AsFixedDoubleArray()->Get(i).is_hole_nan());
-    return data()->AsFixedDoubleArray()->Get(i).get_scalar();
+    return data()->AsFixedDoubleArray()->Get(i);
   }
 }