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

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 1833f3e0c4828abfd2a27e24caa09aa2ee33c3a8..d461ee8d319a16ec4938e7df800e318efc3b14a8 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -713,15 +713,20 @@ LInstruction* LChunkBuilder::DoShift(Token::Value op,
     right = UseRegisterAtStart(right_value);
   }
 
-  // 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);
+    if (may_deopt) {
+      for (HUseIterator it(instr->uses()); !it.Done(); it.Advance()) {
+        if (!it.value()->CheckFlag(HValue::kTruncatingToInt32)) {
+          does_deopt = true;
+          break;
+        }
       }
     }
   }
@@ -880,7 +885,9 @@ 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) {
@@ -1649,7 +1656,10 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
     if (to.IsTagged()) {
       HValue* val = instr->value();
       LOperand* value = UseRegisterAtStart(val);
-      if (val->HasRange() && val->range()->IsInSmiRange()) {
+      if (val->CheckFlag(HInstruction::kUint32)) {
+        LNumberTagU* result = new(zone()) LNumberTagU(value);
+        return AssignEnvironment(AssignPointerMap(DefineSameAsFirst(result)));
+      } else if (val->HasRange() && val->range()->IsInSmiRange()) {
         return DefineAsRegister(new(zone()) LSmiTag(value));
       } else {
         LNumberTagI* result = new(zone()) LNumberTagI(value);
@@ -1657,8 +1667,13 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       }
     } else {
       ASSERT(to.IsDouble());
-      LOperand* value = Use(instr->value());
-      return DefineAsRegister(new(zone()) LInteger32ToDouble(value));
+      if (instr->value()->CheckFlag(HInstruction::kUint32)) {
+        return DefineAsRegister(
+            new(zone()) LUint32ToDouble(UseRegister(instr->value())));
+      } else {
+        return DefineAsRegister(
+            new(zone()) LInteger32ToDouble(Use(instr->value())));
+      }
     }
   }
   UNREACHABLE();