Preserve Smi representation of non-escaping fields.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/251493004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20971 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-escape-analysis.cc

@@ -161,6 +161,23 @@ HValue* HEscapeAnalysisPhase::NewMapCheckAndInsert(HCapturedObject* state,
 }
 
 
+// Replace a field load with a given value, forcing Smi representation if
+// necessary.
+HValue* HEscapeAnalysisPhase::NewLoadReplacement(
+    HLoadNamedField* load, HValue* load_value) {
+  HValue* replacement = load_value;
+  Representation representation = load->representation();
+  if (representation.IsSmi()) {
+    Zone* zone = graph()->zone();
+    HInstruction* new_instr =
+        HForceRepresentation::New(zone, NULL, load_value, representation);
+    new_instr->InsertAfter(load);
+    replacement = new_instr;
+  }
+  return replacement;
+}
+
+
 // Performs a forward data-flow analysis of all loads and stores on the
 // given captured allocation. This uses a reverse post-order iteration
 // over affected basic blocks. All non-escaping instructions are handled
@@ -196,10 +213,11 @@ void HEscapeAnalysisPhase::AnalyzeDataFlow(HInstruction* allocate) {
           int index = load->access().offset() / kPointerSize;
           if (load->object() != allocate) continue;
           ASSERT(load->access().IsInobject());
-          HValue* replacement = state->OperandAt(index);
+          HValue* replacement =
+            NewLoadReplacement(load, state->OperandAt(index));
           load->DeleteAndReplaceWith(replacement);
           if (FLAG_trace_escape_analysis) {
-            PrintF("Replacing load #%d with #%d (%s)\n", instr->id(),
+            PrintF("Replacing load #%d with #%d (%s)\n", load->id(),
                    replacement->id(), replacement->Mnemonic());
           }
           break;

src/hydrogen-escape-analysis.h

@@ -62,6 +62,8 @@ class HEscapeAnalysisPhase : public HPhase {
 
   HValue* NewMapCheckAndInsert(HCapturedObject* state, HCheckMaps* mapcheck);
 
+  HValue* NewLoadReplacement(HLoadNamedField* load, HValue* load_value);
+
   HCapturedObject* StateAt(HBasicBlock* block) {
     return block_states_.at(block->block_id());
   }

test/mjsunit/regress/regress-escape-preserve-smi-representation.js

+// 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.
+
+// Flags: --allow-natives-syntax
+
+function deepEquals(a, b) {
+  if (a === b) { if (a === 0) return (1 / a) === (1 / b); return true; }
+  if (typeof a != typeof b) return false;
+  if (typeof a == "number") return isNaN(a) && isNaN(b);
+  if (typeof a !== "object" && typeof a !== "function") return false;
+  if (objectClass === "RegExp") { return (a.toString() === b.toString()); }
+  if (objectClass === "Function") return false;
+  if (objectClass === "Array") {
+    var elementCount = 0;
+    if (a.length != b.length) { return false; }
+    for (var i = 0; i < a.length; i++) {
+      if (!deepEquals(a[i], b[i])) return false;
+    }
+    return true;
+  }
+}
+
+
+function __f_1(){
+ var __v_0 = [];
+ for(var i=0; i<2; i++){
+   var __v_1=[];
+   __v_0.push([])
+   deepEquals(2, __v_0.length);
+ }
+}
+__f_1();
+%OptimizeFunctionOnNextCall(__f_1);
+__f_1();