X64: Add smi-type to loop variable of simple smi for-loops.

src/x64/codegen-x64.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 1476 matching lines @@
 
   // The break target may be already bound (by the condition), or there
   // may not be a valid frame.  Bind it only if needed.
   if (node->break_target()->is_linked()) {
     node->break_target()->Bind();
   }
   DecrementLoopNesting();
 }
 
 
+void CodeGenerator::SetTypeForStackSlot(Slot* slot, TypeInfo info) {
+  ASSERT(slot->type() == Slot::LOCAL || slot->type() == Slot::PARAMETER);
+  if (slot->type() == Slot::LOCAL) {
+    frame_->SetTypeForLocalAt(slot->index(), info);
+  } else {
+    frame_->SetTypeForParamAt(slot->index(), info);
+  }
+  if (FLAG_debug_code && info.IsSmi()) {
+    if (slot->type() == Slot::LOCAL) {
+      frame_->PushLocalAt(slot->index());
+    } else {
+      frame_->PushParameterAt(slot->index());
+    }
+    Result var = frame_->Pop();
+    var.ToRegister();
+    __ AbortIfNotSmi(var.reg(), "Non-smi value in smi-typed stack slot.");
+  }
+}
+
+
 void CodeGenerator::VisitForStatement(ForStatement* node) {
   ASSERT(!in_spilled_code());
   Comment cmnt(masm_, "[ ForStatement");
   CodeForStatementPosition(node);
 
   // Compile the init expression if present.
   if (node->init() != NULL) {
     Visit(node->init());
   }
 
@@ skipping 73 matching lines @@
         body.Bind();
       }
       break;
     }
     case ALWAYS_FALSE:
       UNREACHABLE();
       break;
   }
 
   CheckStack();  // TODO(1222600): ignore if body contains calls.
+
+  // 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.
+  if (node->is_fast_smi_loop()) {
+    // Set number type of the loop variable to smi.
+    SetTypeForStackSlot(node->loop_variable()->slot(), TypeInfo::Smi());
+  }
+
   Visit(node->body());
 
   // If there is an update expression, compile it if necessary.
   if (node->next() != NULL) {
     if (node->continue_target()->is_linked()) {
       node->continue_target()->Bind();
     }
 
     // Control can reach the update by falling out of the body or by a
     // 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());
     }
   }
 
+  // Set the type of the loop variable to smi before compiling the test
+  // expression if we are in a fast smi loop condition.
+  if (node->is_fast_smi_loop() && has_valid_frame()) {
+    // Set number type of the loop variable to smi.
+    SetTypeForStackSlot(node->loop_variable()->slot(), TypeInfo::Smi());
+  }
+
   // Based on the condition analysis, compile the backward jump as
   // necessary.
   switch (info) {
     case ALWAYS_TRUE:
       if (has_valid_frame()) {
         if (node->next() == NULL) {
           node->continue_target()->Jump();
         } else {
           loop.Jump();
         }
@@ skipping 8547 matching lines @@
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 
 #undef __
 
 } }  // namespace v8::internal