From ea6c05d2c33fd4b29a53122192af32d3d95ab113 Mon Sep 17 00:00:00 2001
From: Victor Gomes <victorgomes@chromium.org>
Date: Fri, 27 Jan 2023 14:44:35 +0100
Subject: [PATCH] [maglev] Pass field representation to
 LoadPolymorphicTaggedField

So we can statically find the returning type in case of a Smi.

Bug: v8:7700
Change-Id: I67f8d1c1c96fef8dc4e246953d9face2c04a9923
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4198152
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Victor Gomes <victorgomes@chromium.org>
Cr-Commit-Position: refs/heads/main@{#85523}
---
 src/maglev/maglev-graph-builder.cc | 14 +++++++++++++-
 src/maglev/maglev-ir.h             | 10 ++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/maglev/maglev-graph-builder.cc b/src/maglev/maglev-graph-builder.cc
index 0f6aeb7b65..6b2161ed64 100644
--- a/src/maglev/maglev-graph-builder.cc
+++ b/src/maglev/maglev-graph-builder.cc
@@ -1397,6 +1397,18 @@ NodeType StaticTypeForNode(ValueNode* node) {
       }
       return NodeType::kHeapObjectWithKnownMap;
     }
+    case Opcode::kLoadPolymorphicTaggedField: {
+      Representation field_representation =
+          node->Cast<LoadPolymorphicTaggedField>()->field_representation();
+      switch (field_representation.kind()) {
+        case Representation::kSmi:
+          return NodeType::kSmi;
+        case Representation::kHeapObject:
+          return NodeType::kAnyHeapObject;
+        default:
+          return NodeType::kUnknown;
+      }
+    }
     case Opcode::kToNumberOrNumeric:
       if (node->Cast<ToNumberOrNumeric>()->mode() ==
           Object::Conversion::kToNumber) {
@@ -2140,7 +2152,7 @@ bool MaglevGraphBuilder::TryBuildNamedAccess(
           {lookup_start_object}, std::move(access_infos)));
     } else {
       SetAccumulator(AddNewNode<LoadPolymorphicTaggedField>(
-          {lookup_start_object}, std::move(access_infos)));
+          {lookup_start_object}, field_repr, std::move(access_infos)));
     }
 
     return true;
diff --git a/src/maglev/maglev-ir.h b/src/maglev/maglev-ir.h
index 14ad252243..a71abdb78f 100644
--- a/src/maglev/maglev-ir.h
+++ b/src/maglev/maglev-ir.h
@@ -4044,8 +4044,11 @@ class LoadPolymorphicTaggedField
 
  public:
   explicit LoadPolymorphicTaggedField(
-      uint64_t bitfield, ZoneVector<compiler::PropertyAccessInfo>&& access_info)
-      : Base(bitfield), access_infos_(access_info) {}
+      uint64_t bitfield, Representation field_representation,
+      ZoneVector<compiler::PropertyAccessInfo>&& access_info)
+      : Base(bitfield),
+        field_representation_(field_representation),
+        access_infos_(access_info) {}
 
   static constexpr OpProperties kProperties = OpProperties::Reading() |
                                               OpProperties::EagerDeopt() |
@@ -4056,12 +4059,15 @@ class LoadPolymorphicTaggedField
   static constexpr int kObjectIndex = 0;
   Input& object_input() { return input(kObjectIndex); }
 
+  Representation field_representation() const { return field_representation_; }
+
   int MaxCallStackArgs() const { return 0; }
   void SetValueLocationConstraints();
   void GenerateCode(MaglevAssembler*, const ProcessingState&);
   void PrintParams(std::ostream&, MaglevGraphLabeller*) const {}
 
  private:
+  Representation field_representation_;
   ZoneVector<compiler::PropertyAccessInfo> access_infos_;
 };