Add test cases for fast smi loops.

src/ia32/codegen-ia32.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
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@@ skipping 3710 matching lines @@
       break;
     }
     case ALWAYS_FALSE:
       UNREACHABLE();
       break;
   }
 
   CheckStack();  // TODO(1222600): ignore if body contains calls.
 
   // If we have (a) a loop with a compile-time constant trip count
   // and (b) the loop induction variable is not assignend inside the

[William Hesse, 2010/03/18 08:52:50]

The added sentence is not capitalized, and has no verb.
How about, instead,

// We know that the loop index is a smi if it is not modified in the loop body
and it is checked against a constant limit in the loop condition.  In this case,
we reset the static type information of the loop index to smi before compiling
the body, the update expression, and the bottom check of the loop condition.

[fschneider, 2010/03/18 09:08:20]

Done.

   // loop we update the number type of the induction variable to be smi.
-
+  // before generating the body, the update expression and the test at
+  // the bottom.
   if (node->is_fast_smi_loop()) {
     // Set number type of the loop variable to smi.
     Slot* slot = node->loop_variable()->slot();
     ASSERT(slot->type() == Slot::LOCAL);
     frame_->SetTypeForLocalAt(slot->index(), NumberInfo::Smi());
     if (FLAG_debug_code) {
       frame_->PushLocalAt(slot->index());
       Result var = frame_->Pop();
       var.ToRegister();
       __ AbortIfNotSmi(var.reg(), "Loop variable not a smi.");
@@ skipping 12 matching lines @@
     // continue.
     if (has_valid_frame()) {
       // Record the source position of the statement as this code which
       // is after the code for the body actually belongs to the loop
       // statement and not the body.
       CodeForStatementPosition(node);
       Visit(node->next());
     }
   }
 
-  // The update expression resets the type of the loop variable. So we
-  // set it to smi before compiling the test expression.
+  // Set the type of the loop variable to smi before compiling the test
+  // expression if we are in a fast smi loop.

[William Hesse, 2010/03/18 08:52:50]

loop condition?

[fschneider, 2010/03/18 09:08:20]

Done.

   if (node->is_fast_smi_loop()) {
     // Set number type of the loop variable to smi.
     Slot* slot = node->loop_variable()->slot();
     ASSERT(slot->type() == Slot::LOCAL);
     frame_->SetTypeForLocalAt(slot->index(), NumberInfo::Smi());
     if (FLAG_debug_code) {
       frame_->PushLocalAt(slot->index());
       Result var = frame_->Pop();
       var.ToRegister();
       __ AbortIfNotSmi(var.reg(), "Loop variable not a smi.");
@@ skipping 8464 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