VPSEL has slightly different semantics under tail predication (it can
end up selecting from Qn, Qm and Qd). We do not model that at the moment
so they block tail predicated loops from being formed.
This just converts them into a predicated VMOV instead (via a VORR),
allowing tail predication to happen whilst still modelling the original
behaviour of the input.
Differential Revision: https://reviews.llvm.org/D85110
As far as I can tell, it should not be necessary for VCTP to be
unpredictable in tail predicated loops. Either it has a a valid loop
counter as a operand which will naturally keep it in the right loop, or
it doesn't and it won't be converted to a tail predicated loop. Not
marking it as having side effects allows it to be scheduled more cleanly
for cases where it is not expected to become a tail predicate loop.
Differential Revision: https://reviews.llvm.org/D83907
Summary:
D65884 added a set of Arm IR intrinsics for the MVE VCTP instruction,
to use in tail predication. But the 64-bit one doesn't work properly:
its predicate type is `<2 x i1>` / `v2i1`, which isn't a legal MVE
type (due to not having a full set of instructions that manipulate it
usefully). The test of `vctp64` in `basic-tail-pred.ll` goes through
`opt` fine, as the test expects, but if you then feed it to `llc` it
causes a type legality failure at isel time.
The usual workaround we've been using in the rest of the MVE
intrinsics family is to bodge `v2i1` into `v4i1`. So I've adjusted the
`vctp64` IR intrinsic to do that, and completely removed the code (and
test) that uses that intrinsic for 64-bit tail predication. That will
allow me to add isel rules (upcoming in D70485) that actually generate
the VCTP64 instruction.
Also renamed all four of these IR intrinsics so that they have `mve`
in the name, since its absence was confusing.
Reviewers: ostannard, MarkMurrayARM, dmgreen
Reviewed By: MarkMurrayARM
Subscribers: samparker, kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70592
Remove any predicate that we replace with a vctp intrinsic, and try
to remove their operands too. Also look into the exit block to see if
there's any duplicates of the predicates that we've replaced and
clone the vctp to be used there instead.
Differential Revision: https://reviews.llvm.org/D67709
llvm-svn: 372567
David Green