Bug 125215 – Avoid to add zero offset in BaseIndex.

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[László Langó]

Avoid to add zero offset in BaseIndex class in offlineasm/cloop.rb.

[László Langó]

Created attachment 218394 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 218394 [details]
Patch

Clearing flags on attachment: 218394

Committed r160091: <http://trac.webkit.org/changeset/160091>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Filip Pizlo]

As a general rule, I would avoid making such changes.  This change has no upside.  The C compiler would have folded the zero, and it would have done it as part of one of many already-mandatory folding passes - even at -O0.  So, you're just duplicating that functionality in offlineasm, which just means more code to maintain and more places where someone might make a mistake.

[László Langó]

(In reply to comment #4)
> As a general rule, I would avoid making such changes.  This change has no upside.  The C compiler would have folded the zero, and it would have done it as part of one of many already-mandatory folding passes - even at -O0.  So, you're just duplicating that functionality in offlineasm, which just means more code to maintain and more places where someone might make a mistake.

Thanks for the reply. Yes, you are partly right. The GCC with -O0 really optimize this out, but the clang isn't. It won't do it with -O0. The other reason why I made this is that there's already a similar change in class Address in this file:
http://trac.webkit.org/browser/trunk/Source/JavaScriptCore/offlineasm/cloop.rb#L195

So we should keep or remove from both places. I'm still think this is a good change.