[csa] Add "Iterate" helper to IteratorBuiltinsAssembler

"Iterate" takes an iterable and a function of TNode<Object>, and
implements the iterator protocol to iterate the iterable, applying the
function to each element.

It handles exceptions thrown during iteration and closes the iterator as
appropriate -- the hope is that if the body of the iteration has no
exception-throwing nodes, TurboFan can dead-code eliminate this close.

In the future, we may want to add an array fast-path to this method;
centralising the implementation means that this fast-path will then be
used by all callers of Iterate.

Change-Id: I9fe2f862b78619fe21ea7cb6469ed7ba93f14a30
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3581770Reviewed-by: Frank Tang <ftang@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80075}

src/builtins/builtins-iterator-gen.cc

@@ -3,13 +3,14 @@
 // found in the LICENSE file.
 
 #include "src/builtins/builtins-iterator-gen.h"
-#include "src/builtins/growable-fixed-array-gen.h"
 
 #include "src/builtins/builtins-collections-gen.h"
 #include "src/builtins/builtins-string-gen.h"
 #include "src/builtins/builtins-utils-gen.h"
 #include "src/builtins/builtins.h"
+#include "src/builtins/growable-fixed-array-gen.h"
 #include "src/codegen/code-stub-assembler.h"
+#include "src/compiler/code-assembler.h"
 #include "src/heap/factory-inl.h"
 
 namespace v8 {
@@ -131,6 +132,55 @@ TNode<Object> IteratorBuiltinsAssembler::IteratorValue(
   return var_value.value();
 }
 
+void IteratorBuiltinsAssembler::Iterate(
+    TNode<Context> context, TNode<Object> iterable,
+    std::function<void(TNode<Object>)> func,
+    std::initializer_list<compiler::CodeAssemblerVariable*> merged_variables) {
+  Iterate(context, iterable, GetIteratorMethod(context, iterable), func,
+          merged_variables);
+}
+
+void IteratorBuiltinsAssembler::Iterate(
+    TNode<Context> context, TNode<Object> iterable, TNode<Object> iterable_fn,
+    std::function<void(TNode<Object>)> func,
+    std::initializer_list<compiler::CodeAssemblerVariable*> merged_variables) {
+  Label done(this);
+
+  IteratorRecord iterator_record = GetIterator(context, iterable, iterable_fn);
+
+  Label if_exception(this, Label::kDeferred);
+  TVARIABLE(Object, var_exception);
+
+  Label loop_start(this, merged_variables);
+  Goto(&loop_start);
+
+  BIND(&loop_start);
+  {
+    TNode<JSReceiver> next = IteratorStep(context, iterator_record, &done);
+    TNode<Object> next_value = IteratorValue(context, next);
+
+    {
+      compiler::ScopedExceptionHandler handler(this, &if_exception,
+                                               &var_exception);
+      func(next_value);
+    }
+
+    Goto(&loop_start);
+  }
+
+  BIND(&if_exception);
+  {
+    TNode<HeapObject> message = GetPendingMessage();
+    SetPendingMessage(TheHoleConstant());
+    IteratorCloseOnException(context, iterator_record);
+    CallRuntime(Runtime::kReThrowWithMessage, context, var_exception.value(),
+                message);
+    Unreachable();
+  }
+
+  BIND(&done);
+}
+
 TNode<JSArray> IteratorBuiltinsAssembler::IterableToList(
     TNode<Context> context, TNode<Object> iterable, TNode<Object> iterator_fn) {
   GrowableFixedArray values(state());
@@ -149,33 +199,26 @@ TNode<FixedArray> IteratorBuiltinsAssembler::IterableToFixedArray(
 void IteratorBuiltinsAssembler::FillFixedArrayFromIterable(
     TNode<Context> context, TNode<Object> iterable, TNode<Object> iterator_fn,
     GrowableFixedArray* values) {
-  // 1. Let iteratorRecord be ? GetIterator(items, method).
-  IteratorRecord iterator_record = GetIterator(context, iterable, iterator_fn);
+  // 1. Let iteratorRecord be ? GetIterator(items, method) (handled by Iterate).
 
   // 2. Let values be a new empty List.
 
   // The GrowableFixedArray has already been created. It's ok if we do this step
   // out of order, since creating an empty List is not observable.
 
-  Label loop_start(this, {values->var_array(), values->var_length(),
-                          values->var_capacity()}),
-      done(this);
-  Goto(&loop_start);
-  // 3. Let next be true.
-  // 4. Repeat, while next is not false
-  BIND(&loop_start);
-  {
-    //  a. Set next to ? IteratorStep(iteratorRecord).
-    TNode<JSReceiver> next = IteratorStep(context, iterator_record, &done);
-    //  b. If next is not false, then
-    //   i. Let nextValue be ? IteratorValue(next).
-    TNode<Object> next_value = IteratorValue(context, next);
-    //   ii. Append nextValue to the end of the List values.
-    values->Push(next_value);
-    Goto(&loop_start);
-  }
-
-  BIND(&done);
+  // 3. Let next be true. (handled by Iterate)
+  // 4. Repeat, while next is not false (handled by Iterate)
+  Iterate(context, iterable, iterator_fn,
+          [&values](TNode<Object> value) {
+            // Handled by Iterate:
+            //  a. Set next to ? IteratorStep(iteratorRecord).
+            //  b. If next is not false, then
+            //   i. Let nextValue be ? IteratorValue(next).
+
+            //   ii. Append nextValue to the end of the List values.
+            values->Push(value);
+          },
+          {values->var_array(), values->var_capacity(), values->var_length()});
 }
 
 TF_BUILTIN(IterableToList, IteratorBuiltinsAssembler) {
@@ -226,56 +269,48 @@ TNode<FixedArray> IteratorBuiltinsAssembler::StringListFromIterable(
   //   a. Return a new empty List.
   GotoIf(IsUndefined(iterable), &done);
 
-  // 2. Let iteratorRecord be ? GetIterator(items).
-  IteratorRecord iterator_record = GetIterator(context, iterable);
+  // 2. Let iteratorRecord be ? GetIterator(items) (handled by Iterate).
 
   // 3. Let list be a new empty List.
 
-  Label loop_start(this,
-                   {list.var_array(), list.var_length(), list.var_capacity()});
-  Goto(&loop_start);
-  // 4. Let next be true.
-  // 5. Repeat, while next is not false
-  Label if_isnotstringtype(this, Label::kDeferred),
-      if_exception(this, Label::kDeferred);
-  BIND(&loop_start);
-  {
-    //  a. Set next to ? IteratorStep(iteratorRecord).
-    TNode<JSReceiver> next = IteratorStep(context, iterator_record, &done);
-    //  b. If next is not false, then
-    //   i. Let nextValue be ? IteratorValue(next).
-    TNode<Object> next_value = IteratorValue(context, next);
-    //   ii. If Type(nextValue) is not String, then
-    GotoIf(TaggedIsSmi(next_value), &if_isnotstringtype);
-    TNode<Uint16T> next_value_type = LoadInstanceType(CAST(next_value));
-    GotoIfNot(IsStringInstanceType(next_value_type), &if_isnotstringtype);
-    //   iii. Append nextValue to the end of the List list.
-    list.Push(next_value);
-    Goto(&loop_start);
-    // 5.b.ii
-    BIND(&if_isnotstringtype);
-    {
-      // 1. Let error be ThrowCompletion(a newly created TypeError object).
-      TVARIABLE(Object, var_exception);
-      {
-        compiler::ScopedExceptionHandler handler(this, &if_exception,
-                                                 &var_exception);
-        CallRuntime(Runtime::kThrowTypeError, context,
-                    SmiConstant(MessageTemplate::kIterableYieldedNonString),
-                    next_value);
-      }
-      Unreachable();
-
-      // 2. Return ? IteratorClose(iteratorRecord, error).
-      BIND(&if_exception);
-      TNode<HeapObject> message = GetPendingMessage();
-      SetPendingMessage(TheHoleConstant());
-      IteratorCloseOnException(context, iterator_record);
-      CallRuntime(Runtime::kReThrowWithMessage, context, var_exception.value(),
-                  message);
-      Unreachable();
-    }
-  }
+  // 4. Let next be true (handled by Iterate).
+  // 5. Repeat, while next is not false (handled by Iterate).
+  Iterate(
+      context, iterable,
+      [&](TNode<Object> next_value) {
+        // Handled by Iterate:
+        //  a. Set next to ? IteratorStep(iteratorRecord).
+        //  b. If next is not false, then
+        //   i. Let nextValue be ? IteratorValue(next).
+
+        //   ii. If Type(nextValue) is not String, then
+        Label if_isnotstringtype(this, Label::kDeferred), loop_body_end(this);
+        GotoIf(TaggedIsSmi(next_value), &if_isnotstringtype);
+        TNode<Uint16T> next_value_type = LoadInstanceType(CAST(next_value));
+        GotoIfNot(IsStringInstanceType(next_value_type), &if_isnotstringtype);
+
+        //   iii. Append nextValue to the end of the List list.
+        list.Push(next_value);
+
+        Goto(&loop_body_end);
+
+        // 5.b.ii
+        BIND(&if_isnotstringtype);
+        {
+          // 1. Let error be ThrowCompletion(a newly created TypeError object).
+
+          CallRuntime(Runtime::kThrowTypeError, context,
+                      SmiConstant(MessageTemplate::kIterableYieldedNonString),
+                      next_value);
+          // 2. Return ? IteratorClose(iteratorRecord, error). (handled by
+          // Iterate).
+          Unreachable();
+        }
+
+        BIND(&loop_body_end);
+      },
+      {list.var_array(), list.var_length(), list.var_capacity()});
+  Goto(&done);
 
   BIND(&done);
   // 6. Return list.

src/builtins/builtins-iterator-gen.h

@@ -50,6 +50,16 @@ class IteratorBuiltinsAssembler : public CodeStubAssembler {
       TNode<Context> context, TNode<JSReceiver> result,
       base::Optional<TNode<Map>> fast_iterator_result_map = base::nullopt);
 
+  void Iterate(TNode<Context> context, TNode<Object> iterable,
+               std::function<void(TNode<Object>)> func,
+               std::initializer_list<compiler::CodeAssemblerVariable*>
+                   merged_variables = {});
+  void Iterate(TNode<Context> context, TNode<Object> iterable,
+               TNode<Object> iterable_fn,
+               std::function<void(TNode<Object>)> func,
+               std::initializer_list<compiler::CodeAssemblerVariable*>
+                   merged_variables = {});
+
   // #sec-iterabletolist
   // Build a JSArray by iterating over {iterable} using {iterator_fn},
   // following the ECMAscript operation with the same name.

src/builtins/builtins-temporal-gen.cc

@@ -33,55 +33,52 @@ TemporalBuiltinsAssembler::TemporalInstantFixedArrayFromIterable(
   //   a. Return a new empty List.
   GotoIf(IsUndefined(iterable), &done);
 
-  // 2. Let iteratorRecord be ? GetIterator(items).
-  IteratorRecord iterator_record = GetIterator(context, iterable);
+  // 2. Let iteratorRecord be ? GetIterator(items) (handled by Iterate).
 
   // 3. Let list be a new empty List.
 
-  Label loop_start(this,
-                   {list.var_array(), list.var_length(), list.var_capacity()});
-  Goto(&loop_start);
-  // 4. Let next be true.
-  // 5. Repeat, while next is not false
-  Label if_isnottemporalinstant(this, Label::kDeferred),
-      if_exception(this, Label::kDeferred);
-  BIND(&loop_start);
-  {
-    //  a. Set next to ? IteratorStep(iteratorRecord).
-    TNode<JSReceiver> next = IteratorStep(context, iterator_record, &done);
-    //  b. If next is not false, then
-    //   i. Let nextValue be ? IteratorValue(next).
-    TNode<Object> next_value = IteratorValue(context, next);
-    //   ii. If Type(nextValue) is not Object or nextValue does not have an
-    //   [[InitializedTemporalInstant]] internal slot
-    GotoIf(TaggedIsSmi(next_value), &if_isnottemporalinstant);
-    TNode<Uint16T> next_value_type = LoadInstanceType(CAST(next_value));
-    GotoIfNot(IsTemporalInstantInstanceType(next_value_type),
-              &if_isnottemporalinstant);
-    //   iii. Append nextValue to the end of the List list.
-    list.Push(next_value);
-    Goto(&loop_start);
-    // 5.b.ii
-    BIND(&if_isnottemporalinstant);
-    {
-      // 1. Let error be ThrowCompletion(a newly created TypeError object).
-      TVARIABLE(Object, var_exception);
-      {
-        compiler::ScopedExceptionHandler handler(this, &if_exception,
-                                                 &var_exception);
-        CallRuntime(Runtime::kThrowTypeError, context,
-                    SmiConstant(MessageTemplate::kIterableYieldedNonString),
-                    next_value);
-      }
-      Unreachable();
-
-      // 2. Return ? IteratorClose(iteratorRecord, error).
-      BIND(&if_exception);
-      IteratorCloseOnException(context, iterator_record);
-      CallRuntime(Runtime::kReThrow, context, var_exception.value());
-      Unreachable();
-    }
-  }
+  // 3. Let next be true. (handled by Iterate).
+  // 4. Repeat, while next is not false (handled by Iterate).
+  Iterate(context, iterable,
+          [&](TNode<Object> next_value) {
+            // Handled by Iterate:
+            //  a. Set next to ? IteratorStep(iteratorRecord).
+            //  b. If next is not false, then
+            //   i. Let nextValue be ? IteratorValue(next).
+
+            //   ii. If Type(nextValue) is not Object or nextValue does not have
+            //   an [[InitializedTemporalInstant]] internal slot
+            Label if_isnottemporalinstant(this, Label::kDeferred),
+                loop_body_end(this);
+            GotoIf(TaggedIsSmi(next_value), &if_isnottemporalinstant);
+            TNode<Uint16T> next_value_type = LoadInstanceType(CAST(next_value));
+            GotoIfNot(IsTemporalInstantInstanceType(next_value_type),
+                      &if_isnottemporalinstant);
+
+            //   iii. Append nextValue to the end of the List list.
+            list.Push(next_value);
+            Goto(&loop_body_end);
+
+            // 5.b.ii
+            BIND(&if_isnottemporalinstant);
+            {
+              // 1. Let error be ThrowCompletion(a newly created TypeError
+              // object).
+              CallRuntime(
+                  Runtime::kThrowTypeError, context,
+                  SmiConstant(MessageTemplate::kIterableYieldedNonString),
+                  next_value);
+
+              // 2. Return ? IteratorClose(iteratorRecord, error). (handled by
+              // Iterate).
+              Unreachable();
+            }
+
+            BIND(&loop_body_end);
+          },
+          {list.var_array(), list.var_length(), list.var_capacity()});
+
+  Goto(&done);
 
   BIND(&done);
   return list.ToFixedArray();