Benjamin Kosnik - Re: Thoughts on LLVM and LTO (original) (raw)

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Okay, but you need to understand that reasonable bounds for compiling the entire program at once are usually 3x-7x more (and in the worst case, even wore) than doing it seperately.

That is the case with completely state of the art algorithms, implementation techniques, etc.

It's just the way the world goes.

It's in no way reasonable to expect to be able to perform IPA optimizations on a 1 million line program in 30 seconds, even if we can compile it normally in 10 seconds.

Tree-SSA managed to add new technology to the compiler without major slowdowns. I'm suggesting that whatever LTO technology is used do the same for non-LTO programs. I consider this reasonable.

Now, I think you are setting the compile time performance bar for LTO awfully low. I'm not asking for new funtionality to be as fast as the current technology without the functionality (although that would certainly be nice, wouldn't it?).

Certainly, icc with IPO is definitely not as slow as you claim.

-benjamin

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