[turbofan] inline %StringIteratorPrototype%.next in JSBuiltinReducer.

src/compiler/js-builtin-reducer.cc

Index: src/compiler/js-builtin-reducer.cc
diff --git a/src/compiler/js-builtin-reducer.cc b/src/compiler/js-builtin-reducer.cc
index 762020438878fdbc5566ba07848fd601c870b6ca..aa38a7f51c01af85dbc1343a72fd8ce81895a1e3 100644
--- a/src/compiler/js-builtin-reducer.cc
+++ b/src/compiler/js-builtin-reducer.cc
@@ -9,11 +9,11 @@
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
+#include "src/compiler/operator-properties.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/compiler/type-cache.h"
 #include "src/compiler/types.h"
 #include "src/objects-inl.h"
-
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ -1026,6 +1026,161 @@ Reduction JSBuiltinReducer::ReduceStringCharCodeAt(Node* node) {
   return NoChange();
 }
 
+Reduction JSBuiltinReducer::ReduceStringIteratorPrototypeNext(Node* node) {
+  Node* receiver = NodeProperties::GetValueInput(node, 1);
+  Node* effect = NodeProperties::GetEffectInput(node);
+  Node* control = NodeProperties::GetControlInput(node);
+  Node* context = NodeProperties::GetContextInput(node);
+  if (HasInstanceTypeWitness(receiver, effect, JS_STRING_ITERATOR_TYPE)) {
+    Node* string = effect = graph()->NewNode(
+        simplified()->LoadField(AccessBuilder::ForJSStringIteratorString()),
+        receiver, effect, control);
+    Node* index = effect = graph()->NewNode(
+        simplified()->LoadField(AccessBuilder::ForJSStringIteratorIndex()),
+        receiver, effect, control);
+    Node* length = effect = graph()->NewNode(
+        simplified()->LoadField(AccessBuilder::ForStringLength()), string,
+        effect, control);
+
+    // branch0: if (index < length)
+    Node* check0 =
+        graph()->NewNode(simplified()->NumberLessThan(), index, length);
+    Node* branch0 =
+        graph()->NewNode(common()->Branch(BranchHint::kTrue), check0, control);
+
+    Node* vtrue0;
+    Node* if_true0 = graph()->NewNode(common()->IfTrue(), branch0);
+    Node* done_true;
+    {
+      done_true = jsgraph()->FalseConstant();
+      Node* lead = graph()->NewNode(simplified()->StringCharCodeAt(), string,
+                                    index, if_true0);
+      Node* check1 = graph()->NewNode(simplified()->NumberLessThan(), lead,
+                                      jsgraph()->Int32Constant(0xD800));
+      Node* branch1 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
+                                       check1, if_true0);
+      Node* vfalse1;
+      Node* if_false1 = graph()->NewNode(common()->IfFalse(), branch1);
+      {
+        Node* check2 = graph()->NewNode(simplified()->NumberLessThanOrEqual(),
+                                        lead, jsgraph()->Int32Constant(0xDC00));
+        Node* branch2 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
+                                         check2, if_false1);
+        Node* vtrue2;
+        Node* if_true2 = graph()->NewNode(common()->IfTrue(), branch2);
+        {
+          Node* next_index = graph()->NewNode(simplified()->NumberAdd(), index,
+                                              jsgraph()->OneConstant());
+          Node* check3 = graph()->NewNode(simplified()->NumberLessThan(),
+                                          next_index, length);
+          Node* branch3 = graph()->NewNode(common()->Branch(BranchHint::kTrue),
+                                           check3, if_true2);
+          Node* vtrue3;
+          Node* if_true3 = graph()->NewNode(common()->IfTrue(), branch3);
+          {
+            Node* trail = graph()->NewNode(simplified()->StringCharCodeAt(),
+                                           string, next_index, if_true3);
+            Node* check4 =
+                graph()->NewNode(simplified()->NumberLessThanOrEqual(),
+                                 jsgraph()->Int32Constant(0xDC00), trail);
+            Node* branch4 = graph()->NewNode(
+                common()->Branch(BranchHint::kTrue), check4, if_true3);
+            Node* vtrue4;
+            Node* if_true4 = graph()->NewNode(common()->IfTrue(), branch4);
+            {
+              Node* check5 =
+                  graph()->NewNode(simplified()->NumberLessThanOrEqual(), trail,
+                                   jsgraph()->Int32Constant(0xDFFF));
+              Node* branch5 = graph()->NewNode(
+                  common()->Branch(BranchHint::kTrue), check5, if_true4);
+              Node* vtrue5;
+              Node* if_true5 = graph()->NewNode(common()->IfTrue(), branch5);
+              {
+                vtrue5 = graph()->NewNode(
+                    simplified()->NumberBitwiseOr(),
+                    graph()->NewNode(simplified()->NumberShiftLeft(), trail,
+                                     jsgraph()->Int32Constant(16)),
+                    lead);
+              }
+
+              Node* if_false5 = graph()->NewNode(common()->IfFalse(), branch5);
+              Node* control =
+                  graph()->NewNode(common()->Merge(2), if_true5, if_false5);
+              vtrue4 = graph()->NewNode(
+                  common()->Phi(MachineRepresentation::kWord32, 2), vtrue5,
+                  lead, control);
+            }
+
+            Node* if_false4 = graph()->NewNode(common()->IfFalse(), branch4);
+            Node* control =
+                graph()->NewNode(common()->Merge(2), if_true4, if_false4);
+            vtrue3 = graph()->NewNode(
+                common()->Phi(MachineRepresentation::kWord32, 2), vtrue4, lead,
+                control);
+          }
+          Node* if_false3 = graph()->NewNode(common()->IfFalse(), branch3);
+          Node* control =
+              graph()->NewNode(common()->Merge(2), if_true3, if_false3);
+          vtrue2 =
+              graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                               vtrue3, lead, control);
+        }
+        Node* if_false2 = graph()->NewNode(common()->IfFalse(), branch2);
+        Node* control =
+            graph()->NewNode(common()->Merge(2), if_true2, if_false2);
+        vfalse1 =
+            graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                             vtrue2, lead, control);
+      }
+      Node* if_true1 = graph()->NewNode(common()->IfTrue(), branch1);
+      Node* control = graph()->NewNode(common()->Merge(2), if_true1, if_false1);
+      Node* codepoint =
+          graph()->NewNode(common()->Phi(MachineRepresentation::kWord32, 2),
+                           vfalse1, lead, control);
+      vtrue0 = graph()->NewNode(
+          simplified()->StringFromCodePoint(UnicodeEncoding::UTF16), codepoint);
+    }
+
+    Node* if_false0 = graph()->NewNode(common()->IfFalse(), branch0);
+    Node* vfalse0;
+    Node* done_false;
+    { done_false = vfalse0 = jsgraph()->UndefinedConstant(); }

[Benedikt Meurer, 2016/09/29 17:19:05]

You should really set done to False in this case, otherwise scalar replacement
will not get rid of the ToBoolean on the .done access for us; plus it violates
the spec.

[caitp, 2016/09/29 17:21:45]

Er, something went wrong here --- this is supposed be `done_false =
jsgraph()->FalseConstant();`. Not sure what happened there, but noted, will fix
that in the next version. Good eye.

+
+    control = graph()->NewNode(common()->Merge(2), if_true0, if_false0);
+    Node* value_phi =
+        graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
+                         vtrue0, vfalse0, control);
+    Node* done_phi =
+        graph()->NewNode(common()->Phi(MachineRepresentation::kTagged, 2),
+                         done_true, done_false, control);
+
+    Node* native_context = effect =
+        graph()->NewNode(jsgraph()->javascript()->LoadContext(
+                             0, Context::NATIVE_CONTEXT_INDEX, true),
+                         context, context, effect);
+    Node* map = effect =
+        graph()->NewNode(jsgraph()->javascript()->LoadContext(
+                             0, Context::ITERATOR_RESULT_MAP_INDEX, true),
+                         context, native_context, effect);
+
+    Node* value = effect = graph()->NewNode(
+        simplified()->Allocate(NOT_TENURED),
+        jsgraph()->Int32Constant(JSIteratorResult::kSize), effect, control);
+    effect = graph()->NewNode(simplified()->StoreField(AccessBuilder::ForMap()),
+                              value, map, effect, control);
+    effect = graph()->NewNode(
+        simplified()->StoreField(AccessBuilder::ForJSIteratorResultDone()),
+        value, done_phi, effect, control);
+    effect = graph()->NewNode(
+        simplified()->StoreField(AccessBuilder::ForJSIteratorResultValue()),
+        value, value_phi, effect, control);
+
+    ReplaceWithValue(node, value, effect, control);
+    return Replace(value);
+  }
+  return NoChange();
+}
+
 Reduction JSBuiltinReducer::ReduceArrayBufferViewAccessor(
     Node* node, InstanceType instance_type, FieldAccess const& access) {
   Node* receiver = NodeProperties::GetValueInput(node, 1);
@@ -1195,6 +1350,8 @@ Reduction JSBuiltinReducer::Reduce(Node* node) {
       return ReduceStringCharAt(node);
     case kStringCharCodeAt:
       return ReduceStringCharCodeAt(node);
+    case kStringIteratorPrototypeNext:
+      return ReduceStringIteratorPrototypeNext(node);
     case kDataViewByteLength:
       return ReduceArrayBufferViewAccessor(
           node, JS_DATA_VIEW_TYPE,