[turbofan] Mark side-effect-free calls to string ops as kEliminatable.

Review-Url: https://codereview.chromium.org/2063373003
Cr-Commit-Position: refs/heads/master@{#36996}

src/compiler/effect-control-linearizer.cc

@@ -1290,6 +1290,7 @@ EffectControlLinearizer::LowerCheckIf(Node* node, Node* frame_state,
                                       Node* effect, Node* control) {
   NodeProperties::ReplaceEffectInput(node, effect);
   NodeProperties::ReplaceControlInput(node, control);
+  DCHECK_NOT_NULL(frame_state);
   node->InsertInput(graph()->zone(), 1, frame_state);
   NodeProperties::ChangeOp(node, common()->DeoptimizeIf());
   return ValueEffectControl(node, node, node);

src/compiler/simplified-lowering.cc

@@ -1509,7 +1509,7 @@ class RepresentationSelector {
         if (lower()) {
           // StringEqual(x, y) => Call(StringEqualStub, x, y, no-context)
           Operator::Properties properties =
-              Operator::kCommutative | Operator::kNoThrow;
+              Operator::kCommutative | Operator::kEliminatable;
           Callable callable = CodeFactory::StringEqual(jsgraph_->isolate());
           CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
           CallDescriptor* desc = Linkage::GetStubCallDescriptor(
@@ -1519,7 +1519,6 @@ class RepresentationSelector {
                             jsgraph_->HeapConstant(callable.code()));
           node->AppendInput(jsgraph_->zone(), jsgraph_->NoContextConstant());
           node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
-          node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
           NodeProperties::ChangeOp(node, jsgraph_->common()->Call(desc));
         }
         return;
@@ -1528,7 +1527,7 @@ class RepresentationSelector {
         VisitBinop(node, UseInfo::AnyTagged(), MachineRepresentation::kTagged);
         if (lower()) {
           // StringLessThan(x, y) => Call(StringLessThanStub, x, y, no-context)
-          Operator::Properties properties = Operator::kNoThrow;
+          Operator::Properties properties = Operator::kEliminatable;
           Callable callable = CodeFactory::StringLessThan(jsgraph_->isolate());
           CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
           CallDescriptor* desc = Linkage::GetStubCallDescriptor(
@@ -1538,7 +1537,6 @@ class RepresentationSelector {
                             jsgraph_->HeapConstant(callable.code()));
           node->AppendInput(jsgraph_->zone(), jsgraph_->NoContextConstant());
           node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
-          node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
           NodeProperties::ChangeOp(node, jsgraph_->common()->Call(desc));
         }
         return;
@@ -1548,7 +1546,7 @@ class RepresentationSelector {
         if (lower()) {
           // StringLessThanOrEqual(x, y)
           //   => Call(StringLessThanOrEqualStub, x, y, no-context)
-          Operator::Properties properties = Operator::kNoThrow;
+          Operator::Properties properties = Operator::kEliminatable;
           Callable callable =
               CodeFactory::StringLessThanOrEqual(jsgraph_->isolate());
           CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
@@ -1559,7 +1557,6 @@ class RepresentationSelector {
                             jsgraph_->HeapConstant(callable.code()));
           node->AppendInput(jsgraph_->zone(), jsgraph_->NoContextConstant());
           node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
-          node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
           NodeProperties::ChangeOp(node, jsgraph_->common()->Call(desc));
         }
         return;
@@ -1573,7 +1570,7 @@ class RepresentationSelector {
         VisitUnop(node, UseInfo::AnyTagged(), MachineRepresentation::kTagged);
         if (lower()) {
           // StringToNumber(x) => Call(StringToNumber, x, no-context)
-          Operator::Properties properties = Operator::kNoThrow;
+          Operator::Properties properties = Operator::kEliminatable;
           Callable callable = CodeFactory::StringToNumber(jsgraph_->isolate());
           CallDescriptor::Flags flags = CallDescriptor::kNoFlags;
           CallDescriptor* desc = Linkage::GetStubCallDescriptor(
@@ -1583,7 +1580,6 @@ class RepresentationSelector {
                             jsgraph_->HeapConstant(callable.code()));
           node->AppendInput(jsgraph_->zone(), jsgraph_->NoContextConstant());
           node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
-          node->AppendInput(jsgraph_->zone(), jsgraph_->graph()->start());
           NodeProperties::ChangeOp(node, jsgraph_->common()->Call(desc));
         }
         return;

test/mjsunit/compiler/regress-string-to-number-add.js

+// Copyright 2016 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.
+
+// Flags: --allow-natives-syntax --turbo-type-feedback
+
+function f(x) {
+  var s = x ? "0" : "1";
+  return 1 + Number(s);
+}
+
+f(0);
+f(0);
+%OptimizeFunctionOnNextCall(f);
+assertEquals(2, f(0));