[llvm-dev] RFC: speedups with instruction side-data (ADCE, perhaps others?)

[Daniel Berlin via llvm-dev]

On Tue, Sep 15, 2015 at 7:16 PM, escha <escha at apple.com> wrote:
> You mean the input test data? I was testing performance using our offline perf suite (which is a ton of out of tree code), so it’s not something I can share, but I imagine any similar test suite put through a typical compiler pipeline will exercise ADCE in similar ways. ADCE’s cost is pretty much the sum of (cost of managing the set) + (cost of eraseinstruction), which in our case turns out to be 1/3 the former and 2/3 the latter (roughly).

I asked because I can't really reproduce the results of your massive
speedups on even the larger testcases i have around, certainly not on
the order you reported.

I can get a speedup of about 10%  by changing the smallptrsetsize to
be 16 from 128.
I can get a reduction of about 15% by using a visited bit (IE half the
speedup you report).
I can get roughly the same speedup by using denseset, etc.