[llvm-dev] RFC: New aggressive dead code elimination pass

[Justin Bogner via llvm-dev]

David Callahan via llvm-dev <llvm-dev at lists.llvm.org> writes:
> Hi,
>
> I have a new variant of Aggressive Dead Code Elimination that also
> removes dead branching. It is designed to minimize the cost of
> control-dependence analysis in the common case where almost the entire
> program is live. It also can optionally remove dead but
> may-be-infinite loops.
>
> When enabled for –O3 (replacing current ADCE pass) and removing loops,
> impact on SPEC2006 is in the noise but it impacts internal benchmarks
> suites 1-2% with a comparable increase in compile time.  My
> expectation would be to enable –O3 only until we have some experience
> with cost but I suspect it should be fine –O2.

Just to clarify, you're saying that both runtime and compile time impact
were in the noise on SPEC, right?

> What information would the community like to see about such a change
> before I put up a diff and (including tweaks to unit tests).

I'm not sure that there's much to discuss in the abstract - it's much
easier to evaluate this kind of thing when there's a patch to refer to.
Presumably people will want to try the patch out on their own internal
benchmarks as well.

> Thanks
> david
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