[webkit-reviews] review granted: [Bug 172793] GC should use scrambled free-lists : [Attachment 311783] the patch

[bugzilla-daemon at webkit.org]

Mark Lam <mark.lam at apple.com> has granted Filip Pizlo <fpizlo at apple.com>'s
request for review:
Bug 172793: GC should use scrambled free-lists
https://bugs.webkit.org/show_bug.cgi?id=172793

Attachment 311783: the patch

https://bugs.webkit.org/attachment.cgi?id=311783&action=review




--- Comment #28 from Mark Lam <mark.lam at apple.com> ---
Comment on attachment 311783
  --> https://bugs.webkit.org/attachment.cgi?id=311783
the patch

View in context: https://bugs.webkit.org/attachment.cgi?id=311783&action=review

r=me

> Source/JavaScriptCore/ChangeLog:3
> +	   GC should use a scrambled free-list

Please update to match your changed bug title.

> Source/JavaScriptCore/jit/AssemblyHelpers.h:1494
> +	   if (isX86())
> +	       xorPtr(Address(allocatorGPR, MarkedAllocator::offsetOfFreeList()
+ FreeList::offsetOfSecret()), resultGPR);
> +	   else {
> +	       loadPtr(Address(allocatorGPR,
MarkedAllocator::offsetOfFreeList() + FreeList::offsetOfSecret()), scratchGPR);
> +	       xorPtr(scratchGPR, resultGPR);
> +	   }

Do we still need to have this conditional on isX86() given that you've added
the xorPtr impls for ARM64 and ARMv7?  Maybe make it #if CPU(...) to be nice to
other ports that don't have the xorPtr(Address src, RegisterID dest) impl yet? 
Otherwise, they get a build failure.