By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), July 15, 2013 7:45 pm
Room: Moderated Discussions
bakaneko (nyan.delete@this.hyan.wan) on July 15, 2013 7:47 pm wrote:
>
> As someone who works for ARM as compiler writer,
> why don't you tell us in more detail how Intel
> cheated?
Exophase's post to anandtech was quoted here earlier, I think. It has the relevant details:
http://forums.anandtech.com/showthread.php?t=2330027
and quite frankly, while optimizing multiple bit operations into a word is a very valid optimization, the code icc generates there seems a fair bit past that.
Sure, it could in theory happen with a really smart compiler and lots of generic optimizations. In practice? It really smells like the compiler actively targeting a very particular code-sequence. IOW, compiler cheating. The timing that Exophase points out makes it look worse.
And Wilco is right that it smells pretty bad when AnTuTu seems to be so close to intel, and seem to have bent over backwards using recent versions of icc etc.
It's all "explainable". But it doesn't pass the smell test.
Linus
>
> As someone who works for ARM as compiler writer,
> why don't you tell us in more detail how Intel
> cheated?
Exophase's post to anandtech was quoted here earlier, I think. It has the relevant details:
http://forums.anandtech.com/showthread.php?t=2330027
and quite frankly, while optimizing multiple bit operations into a word is a very valid optimization, the code icc generates there seems a fair bit past that.
Sure, it could in theory happen with a really smart compiler and lots of generic optimizations. In practice? It really smells like the compiler actively targeting a very particular code-sequence. IOW, compiler cheating. The timing that Exophase points out makes it look worse.
And Wilco is right that it smells pretty bad when AnTuTu seems to be so close to intel, and seem to have bent over backwards using recent versions of icc etc.
It's all "explainable". But it doesn't pass the smell test.
Linus
