Allow uint32 value on optimized frames if they are consumed by safe operations.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 8613048f09f3d3f53bb34c4bc6b6a6cda4cb1be2..f41a18e7b1656c4d7d30c4720885e81539473e7b 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -738,15 +738,20 @@ LInstruction* LChunkBuilder::DoShift(Token::Value op,
     right = UseFixed(right_value, ecx);
   }
 
-  // Shift operations can only deoptimize if we do a logical shift by 0 and
-  // the result cannot be truncated to int32.
-  bool may_deopt = (op == Token::SHR && constant_value == 0);
   bool does_deopt = false;
-  if (may_deopt) {
-    for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
-      if (!it.value()->CheckFlag(HValue::kTruncatingToInt32)) {
-        does_deopt = true;
-        break;
+  if (FLAG_opt_safe_uint32_operations) {
+    does_deopt = !instr->CheckFlag(HInstruction::kUint32);
+  } else {
+    // Shift operations can only deoptimize if we do a logical shift by 0 and
+    // the result cannot be truncated to int32.
+    bool may_deopt = (op == Token::SHR && constant_value == 0 &&
+      !instr->CheckFlag(HInstruction::kUint32));
+    if (may_deopt) {
+      for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
+        if (!it.value()->CheckFlag(HValue::kTruncatingToInt32)) {
+          does_deopt = true;
+          break;
+        }
       }
     }
   }
@@ -906,7 +911,9 @@ LEnvironment* LChunkBuilder::CreateEnvironment(
     } else {
       op = UseAny(value);
     }
-    result->AddValue(op, value->representation());
+    result->AddValue(op,
+                     value->representation(),
+                     value->CheckFlag(HInstruction::kUint32));
   }
 
   if (hydrogen_env->frame_type() == JS_FUNCTION) {
@@ -1698,14 +1705,24 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       LOperand* value = UseRegister(val);
       if (val->HasRange() && val->range()->IsInSmiRange()) {
         return DefineSameAsFirst(new(zone()) LSmiTag(value));
+      } else if (val->CheckFlag(HInstruction::kUint32)) {
+        LOperand* temp = FixedTemp(xmm1);
+        LNumberTagU* result = new(zone()) LNumberTagU(value, temp);
+        return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
       } else {
         LNumberTagI* result = new(zone()) LNumberTagI(value);
         return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
       }
     } else {
       ASSERT(to.IsDouble());
-      return DefineAsRegister(
-          new(zone()) LInteger32ToDouble(Use(instr->value())));
+      if (instr->value()->CheckFlag(HInstruction::kUint32)) {
+        LOperand* temp = FixedTemp(xmm1);
+        return DefineAsRegister(
+            new(zone()) LUint32ToDouble(UseRegister(instr->value()), temp));
+      } else {
+        return DefineAsRegister(
+            new(zone()) LInteger32ToDouble(Use(instr->value())));
+      }
     }
   }
   UNREACHABLE();