Add DemandedElts support inside the TRUNCATE analysis.
REAPPLIED - this was reverted by @hans at rGa51226057fc3 due to an issue with vector shift amount types, which was fixed in rG935bacd3a724 and an additional test case added at rG0ca81b90d19d
Differential Revision: https://reviews.llvm.org/D56387
It caused "Vector shift amounts must be in the same as their first arg"
asserts in Chromium builds. See the code review for repro instructions.
> Add DemandedElts support inside the TRUNCATE analysis.
>
> Differential Revision: https://reviews.llvm.org/D56387
This reverts commit cad4275d69.
This adds an extra tablegen PatFrag, zanyext, which matches either any
extend or zext and uses that in the aarch64 backend to handle any
extends in addw/addl/subw/subl patterns.
Differential Revision: https://reviews.llvm.org/D93833
Demanded bits may turn a sext or zext into an anyext if the top bits are
not needed. This currently prevents the lowering to instructions like
mull, addl and addw. This patch fixes the mull generation by keeping it
simple and treating them like zextends.
Differential Revision: https://reviews.llvm.org/D93832
Simon Pilgrim