[turbofan] Re-separate logic for LET and CONST in BuildVariableAssignment

src/compiler/ast-graph-builder.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
@@ skipping 3435 matching lines @@
         if (is_strict(language_mode())) {
           return BuildThrowConstAssignError(bailout_id);
         }
         return value;
       } else if (mode == LET && op == Token::INIT) {
         // No initialization check needed because scoping guarantees it. Note
         // that we still perform a lookup to keep the variable live, because
         // baseline code might contain debug code that inspects the variable.
         Node* current = environment()->Lookup(variable);
         CHECK_NOT_NULL(current);
+      } else if (mode == LET && op != Token::INIT &&
+                 variable->binding_needs_init()) {
+        // Perform an initialization check for let declared variables.
+        Node* current = environment()->Lookup(variable);
+        if (current->op() == the_hole->op()) {
+          return BuildThrowReferenceError(variable, bailout_id);
+        } else if (current->opcode() == IrOpcode::kPhi) {
+          BuildHoleCheckThenThrow(current, variable, value, bailout_id);
+        }
       } else if (mode == CONST && op == Token::INIT) {
         // Perform an initialization check for const {this} variables.
         // Note that the {this} variable is the only const variable being able
         // to trigger bind operations outside the TDZ, via {super} calls.
         Node* current = environment()->Lookup(variable);
         if (current->op() != the_hole->op() && variable->is_this()) {
           value = BuildHoleCheckElseThrow(current, variable, value, bailout_id);
         }
-      } else if (IsLexicalVariableMode(mode) && op != Token::INIT) {
-        // Perform an initialization check for lexically declared variables.
-        Node* current = environment()->Lookup(variable);
+      } else if (mode == CONST && op != Token::INIT) {
         if (variable->binding_needs_init()) {
+          Node* current = environment()->Lookup(variable);
           if (current->op() == the_hole->op()) {
             return BuildThrowReferenceError(variable, bailout_id);
           } else if (current->opcode() == IrOpcode::kPhi) {
             BuildHoleCheckThenThrow(current, variable, value, bailout_id);
           }
         }
-        if (mode == CONST) {
-          return BuildThrowConstAssignError(bailout_id);
-        }
+        // Assignment to const is exception in all modes.
+        return BuildThrowConstAssignError(bailout_id);
       }
       environment()->Bind(variable, value);
       return value;
     case VariableLocation::CONTEXT: {
       // Context variable (potentially up the context chain).
       int depth = current_scope()->ContextChainLength(variable->scope());
       if (mode == CONST_LEGACY && op != Token::INIT) {
         // Non-initializing assignment to legacy const is
         // - exception in strict mode.
         // - ignored in sloppy mode.
         if (is_strict(language_mode())) {
           return BuildThrowConstAssignError(bailout_id);
         }
         return value;
+      } else if (mode == LET && op != Token::INIT &&
+                 variable->binding_needs_init()) {
+        // Perform an initialization check for let declared variables.
+        const Operator* op =
+            javascript()->LoadContext(depth, variable->index(), false);
+        Node* current = NewNode(op, current_context());
+        value = BuildHoleCheckThenThrow(current, variable, value, bailout_id);
       } else if (mode == CONST && op == Token::INIT) {
         // Perform an initialization check for const {this} variables.
         // Note that the {this} variable is the only const variable being able
         // to trigger bind operations outside the TDZ, via {super} calls.
         if (variable->is_this()) {
           const Operator* op =
               javascript()->LoadContext(depth, variable->index(), false);
           Node* current = NewNode(op, current_context());
           value = BuildHoleCheckElseThrow(current, variable, value, bailout_id);
         }
-      } else if (IsLexicalVariableMode(mode) && op != Token::INIT) {
-        // Perform an initialization check for lexically declared variables.
+      } else if (mode == CONST && op != Token::INIT) {
         if (variable->binding_needs_init()) {
           const Operator* op =
               javascript()->LoadContext(depth, variable->index(), false);
           Node* current = NewNode(op, current_context());
-          value = BuildHoleCheckThenThrow(current, variable, value, bailout_id);
+          BuildHoleCheckThenThrow(current, variable, value, bailout_id);
         }
-        if (mode == CONST) {
-          // Assignment to const is exception in all modes.
-          return BuildThrowConstAssignError(bailout_id);
-        }
+        // Assignment to const is exception in all modes.
+        return BuildThrowConstAssignError(bailout_id);
       }
       const Operator* op = javascript()->StoreContext(depth, variable->index());
       return NewNode(op, current_context(), value);
     }
     case VariableLocation::LOOKUP: {
       // Dynamic lookup of context variable (anywhere in the chain).
       Handle<Name> name = variable->name();
       Node* store = BuildDynamicStore(name, value);
       PrepareFrameState(store, bailout_id, combine);
       return store;
@@ skipping 797 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8