Use a Torque macro for searching context locals

This is a partial reland of https://crrev.com/c/v8/v8/+/2601880 .

This change improves readability and helps prepare for when ScopeInfo
will not be convertible to FixedArrayBase.

Change-Id: I8de453c2b72ced51e98161e3d9e6426cd6ff7267
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2707250Reviewed-by: Mythri Alle <mythria@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#72920}

src/codegen/code-stub-assembler.cc

@@ -2013,11 +2013,6 @@ TNode<IntPtrT> CodeStubAssembler::LoadArrayLength(
   return LoadAndUntagWeakFixedArrayLength(array);
 }
 
-template <>
-TNode<IntPtrT> CodeStubAssembler::LoadArrayLength(TNode<ScopeInfo> array) {
-  return LoadAndUntagFixedArrayBaseLength(array);
-}
-
 template <typename Array, typename TIndex, typename TValue>
 TNode<TValue> CodeStubAssembler::LoadArrayElement(
     TNode<Array> array, int array_header_size, TNode<TIndex> index_node,
@@ -2048,10 +2043,6 @@ TNode<TValue> CodeStubAssembler::LoadArrayElement(
 template V8_EXPORT_PRIVATE TNode<MaybeObject>
 CodeStubAssembler::LoadArrayElement<TransitionArray, IntPtrT>(
     TNode<TransitionArray>, int, TNode<IntPtrT>, int, LoadSensitivity);
-template V8_EXPORT_PRIVATE TNode<MaybeObject>
-CodeStubAssembler::LoadArrayElement<ScopeInfo, IntPtrT>(TNode<ScopeInfo>, int,
-                                                        TNode<IntPtrT>, int,
-                                                        LoadSensitivity);
 
 template <typename TIndex>
 TNode<Object> CodeStubAssembler::LoadFixedArrayElement(

src/ic/accessor-assembler.cc

@@ -3074,35 +3074,15 @@ void AccessorAssembler::ScriptContextTableLookup(
     TNode<ScopeInfo> scope_info =
         CAST(LoadContextElement(script_context, Context::SCOPE_INFO_INDEX));
 
-    TVARIABLE(IntPtrT, scope_var_index,
-              IntPtrConstant(ScopeInfo::kVariablePartIndex - 1));
-    TNode<IntPtrT> num_scope_vars = SmiUntag(
-        CAST(LoadObjectField(scope_info, ScopeInfo::kContextLocalCountOffset)));
-    TNode<IntPtrT> end_index = IntPtrAdd(
-        num_scope_vars, IntPtrConstant(ScopeInfo::kVariablePartIndex));
-    Label loop_scope_info(this, &scope_var_index);
-    Goto(&loop_scope_info);
-
-    BIND(&loop_scope_info);
-    {
-      scope_var_index = IntPtrAdd(scope_var_index.value(), IntPtrConstant(1));
-      GotoIf(IntPtrGreaterThanOrEqual(scope_var_index.value(), end_index),
-             &loop);
-
-      FixedArrayBoundsCheck(scope_info, scope_var_index.value(), 0);
-      TNode<Object> var_name = CAST(LoadArrayElement(
-          scope_info, FixedArray::kHeaderSize, scope_var_index.value()));
-      GotoIf(TaggedNotEqual(var_name, name), &loop_scope_info);
-
-      TNode<IntPtrT> var_index =
-          IntPtrAdd(IntPtrConstant(Context::MIN_CONTEXT_SLOTS),
-                    IntPtrSub(scope_var_index.value(),
-                              IntPtrConstant(ScopeInfo::kVariablePartIndex)));
+    TNode<IntPtrT> context_local_index =
+        IndexOfLocalName(scope_info, name, &loop);
+
+    TNode<IntPtrT> var_index = IntPtrAdd(
+        IntPtrConstant(Context::MIN_CONTEXT_SLOTS), context_local_index);
     TNode<Object> result = LoadContextElement(script_context, var_index);
     GotoIf(IsTheHole(result), found_hole);
     Return(result);
   }
-  }
 }
 
 void AccessorAssembler::LoadGlobalIC_NoFeedback(TNode<Context> context,

src/objects/scope-info.tq

@@ -167,3 +167,17 @@ extern class ScopeInfo extends FixedArrayBase {
   module_variables[flags.scope_type == ScopeType::MODULE_SCOPE ? module_variable_count[0] : 0]:
       ModuleVariable;
 }
+
+// Returns the index of the named local in a ScopeInfo.
+// Assumes that the given name is internalized; uses pointer comparisons.
+@export
+macro IndexOfLocalName(scopeInfo: ScopeInfo, name: Name):
+    intptr labels NotFound {
+  const count: intptr = Convert<intptr>(scopeInfo.context_local_count);
+  for (let i: intptr = 0; i < count; ++i) {
+    if (TaggedEqual(name, scopeInfo.context_local_names[i])) {
+      return i;
+    }
+  }
+  goto NotFound;
+}