[LLVMdev] OptimizeMemoryInst(...) scaling

[Rafael Espíndola]

Can you report a bug with an IL testcase?

On 19 November 2012 17:13, Cameron McInally <cameron.mcinally at nyu.edu> wrote:
> Hey guys,
>
> I'm working on the S3D Benchmark and notice that
> CodeGenPrepare::OptimizeMemoryInst(...) in
> lib/Transforms/Scalar/CodeGenPrepare.cpp isn't scaling well. A whopping
> 99.3% of the compilation time for one file is spent in this function. The
> User Time for this compilation is 3166 seconds with a stock LLVM 3.1. If I
> disable the calls to OptimizeMemoryInst(...), the compilation time drops to
> 76 seconds.
>
> It appears that OptimizeMemoryInst(...) was tweaked for compilation time
> improvements in the past, but unfortunately, this particular case was not
> covered. S3D has lots of matrix element references. For these references,
> our proprietary optimizer has already sunk the addressing code so that it
> shows up in the reference's Basic Block. OptimizeMemoryInst(...) ends up
> returning early with no changes made for almost every load/store in this
> particular file of S3D.
>
> Before I try to tackle this issue, I would like to find out if
> CodeGenPrepare::OptimizeMemoryInst(...) has attracted anyone's attention
> already. If so, any insight into this problem would be appreciated.
>
> If it helps, it's clear that the lion's share of time spent in
> OptimizeMemoryInst(...) is actually spent matching the address mode of the
> loads/stores with AddressingModeMatcher::MatchAddr(...).
>
> Thanks,
> Cameron
>
>
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