Preserve Smi representation of non-escaping fields.

src/hydrogen-escape-analysis.cc

Index: src/hydrogen-escape-analysis.cc
diff --git a/src/hydrogen-escape-analysis.cc b/src/hydrogen-escape-analysis.cc
index 102301992333e1c9a994d0d7b051577869ac89fa..3b00866e650f7bdcd9d8783ff680bb221041abba 100644
--- a/src/hydrogen-escape-analysis.cc
+++ b/src/hydrogen-escape-analysis.cc
@@ -161,6 +161,27 @@ HValue* HEscapeAnalysisPhase::NewMapCheckAndInsert(HCapturedObject* state,
 }
 
 
+// Replace a field load with a given value, forcing Smi representation if
+// necessary.
+void HEscapeAnalysisPhase::ReplaceFieldLoadWithValue(
+    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;
+  }
+  load->DeleteAndReplaceWith(replacement);

[Michael Starzinger, 2014/04/25 11:08:09]

nit: I was actually thinking along the lines of having the DeleteAndReplaceWith
plus the printing outside. And the helper would really just be a
"NewLoadReplacement" that returns some other node as a replacement. Thereby
mutation of the existing graph is in the data-flow analysis code.

+  if (FLAG_trace_escape_analysis) {
+    PrintF("Replacing load #%d with #%d (%s)\n", load->id(),
+           replacement->id(), replacement->Mnemonic());
+  }
+}
+
+
 // 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
@@ -196,12 +217,7 @@ 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);
-          load->DeleteAndReplaceWith(replacement);
-          if (FLAG_trace_escape_analysis) {
-            PrintF("Replacing load #%d with #%d (%s)\n", instr->id(),
-                   replacement->id(), replacement->Mnemonic());
-          }
+          ReplaceFieldLoadWithValue(load, state->OperandAt(index));
           break;
         }
         case HValue::kStoreNamedField: {