[PATCH] D51664: [IR] Lazily number instructions for local dominance queries

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

In https://reviews.llvm.org/D51664#1243763, @sanjoy wrote:

> > The downside is that Instruction grows from 56 bytes to 64 bytes, and I don't have a good way to measure what that costs in practice.
>
> In the commit that removed the table you said "Removing the virtual table pointer from Value saves 1% of RSS when doing LTO of llc on Linux."; so I'd expect the regression to be in the same ballpark?


I've started running a full LTO step of llc, but it's taking quite a while (>20min). I recall I picked LTO of llc last time because it completed in a few minutes, so I could repeat the measurement a few times to build confidence that it wasn't noise. Something may have changed. :( We'll see what comes back soon, I guess.

If I get no results, at least 1% RSS is an upper bound on increased LTO memory usage. I'm happy to trade that for 40% shorter compile time of the slowest TUs in clang.


https://reviews.llvm.org/D51664