[llvm-dev] High memory use and LVI/Correlated Value Propagation

[Daniel Berlin via llvm-dev]

On Wed, Jan 13, 2016 at 4:23 PM, Joerg Sonnenberger via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> On Wed, Jan 13, 2016 at 03:38:24PM -0800, Philip Reames wrote:
> > I don't think that arbitrary limiting the complexity of the search is the
> > right approach.  There are numerous ways the LVI infrastructure could be
> > made more memory efficient.  Fixing the existing code to be memory
> efficient
> > is the right approach.  Only once there's no more low hanging fruit
> should
> > we even consider clamping the search.
>
> Memory efficiency is only half of the problem. I.e. groonga's expr.c
> needs 4m to build on my laptop, a 2.7GHz i7. That doesn't sound
> reasonable for a -O2. Unlike the GVN issue, the cases I have run into do
> finish after a(n unreasonable) while, so at least it is not trivially
> superlinear.
>


Okay, so rather than artificially limit stuff, we should see if we can fix
the efficiency of the algorithms.

CVP is an O(N*lattice height) pass problem. It sounds like it is being more
than that for you.
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