tree 464e32479a62f78fb9163cd2c813825d3fc85dbb
parent 71d88cebfb42c8c5ac2d54b42afdcca956e55660
author Florian Hahn <flo@fhahn.com> 1593804171 +0100
committer Florian Hahn <flo@fhahn.com> 1593804171 +0100

[InstCombine] Try to narrow expr if trunc cannot be removed.

Narrowing an input expression of a truncate to a type larger than the
result of the truncate won't allow removing the truncate, but it may
enable further optimizations, e.g. allowing for larger vectorization
factors.

For now this is intentionally limited to integer types only, to avoid
producing new vector ops that might not be suitable for the target.

If we know that the only user is a trunc, we can also be allow more
cases, e.g. also shortening expressions with some additional shifts.

I would appreciate feedback on the best place to do such a narrowing.

This fixes PR43580.

Reviewers: spatel, RKSimon, lebedev.ri, xbolva00

Reviewed By: lebedev.ri

Differential Revision: https://reviews.llvm.org/D82973