Speed up conversion of untagged int32 result if we know it must be a smi.

src/ia32/codegen-ia32.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 472 matching lines @@
 }
 
 
 void CodeGenerator::LoadInSafeInt32Mode(Expression* expr,
                                          BreakTarget* unsafe_bailout) {
   set_unsafe_bailout(unsafe_bailout);
   set_in_safe_int32_mode(true);
   Load(expr);
   Result value = frame_->Pop();
   ASSERT(frame_->HasNoUntaggedInt32Elements());
-  ConvertInt32ResultToNumber(&value);
+  if (expr->GuaranteedSmiResult()) {
+    ConvertInt32ResultToSmi(&value);
+  } else {
+    ConvertInt32ResultToNumber(&value);
+  }
   set_in_safe_int32_mode(false);
   set_unsafe_bailout(NULL);
   frame_->Push(&value);
 }
 
 
 void CodeGenerator::LoadWithSafeInt32ModeDisabled(Expression* expr) {
   set_safe_int32_mode_enabled(false);
   Load(expr);
   set_safe_int32_mode_enabled(true);
 }
 
 
+void CodeGenerator::ConvertInt32ResultToSmi(Result* value) {
+  ASSERT(value->is_untagged_int32());
+  if (value->is_register()) {
+    __ add(value->reg(), Operand(value->reg()));
+  } else {
+    ASSERT(value->is_constant());
+    ASSERT(value->handle()->IsSmi());
+  }
+  value->set_untagged_int32(false);
+  value->set_number_info(NumberInfo::Smi());
+}
+
+
 void CodeGenerator::ConvertInt32ResultToNumber(Result* value) {
   ASSERT(value->is_untagged_int32());
   if (value->is_register()) {
     Register val = value->reg();
     JumpTarget done;
     __ add(val, Operand(val));
     done.Branch(no_overflow, value);
     __ sar(val, 1);
     // If there was an overflow, bits 30 and 31 of the original number disagree.
     __ xor_(val, 0x80000000u);
@@ skipping 28 matching lines @@
     RegisterFile empty_regs;
     SetFrame(clone, &empty_regs);
     __ bind(&allocation_failed);
     unsafe_bailout_->Jump();
 
     done.Bind(value);
   } else {
     ASSERT(value->is_constant());
   }
   value->set_untagged_int32(false);
+  value->set_number_info(NumberInfo::Integer32());
 }
 
 
 void CodeGenerator::Load(Expression* expr) {
 #ifdef DEBUG
   int original_height = frame_->height();
 #endif
   ASSERT(!in_spilled_code());
 
   // If the expression should be a side-effect-free 32-bit int computation,
@@ skipping 11974 matching lines @@
 
   // Call the runtime; it returns -1 (less), 0 (equal), or 1 (greater)
   // tagged as a small integer.
   __ bind(&runtime);
   __ TailCallRuntime(Runtime::kStringCompare, 2, 1);
 }
 
 #undef __
 
 } }  // namespace v8::internal