[LLVMdev] PATCH: Use size reduction -- wave2
sabre at nondot.org
Wed Apr 16 19:12:33 PDT 2008
On Apr 16, 2008, at 11:25 AM, Dan Gohman wrote:
>> So, my idea is that these changes are performance neutral.
I strongly agree with Dan that we need to measure performance to
ensure there is no significant performance regression.
>> I hope that this is interesting, but I'd like to ask anybody who is
>> comfortable with performance testing to help provide some hard
>> data :-)
> I agree that performance testing is not easy and requires resources,
> but I'm curious what's motivating this project here. My assumption
> has been that no one would likely go to the extreme of inventing a
> mini-language encoded in the least significant bits of pointer
> members in successive structs unless they were pretty desperate for
> performance or scalability.
Ah, this question is easy: it shrinks the Use class by a word, which
reduces the most popular class in the LLVM IR by 25%. This directly
makes all binary operators 8 bytes smaller for example, which is a
pretty big memory footprint win, and memory footprint translates to
dcache efficiency as well.
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