[PATCH] D125956: [NOT YET FOR REVIEW][AArch64][LV] Implement AArch64TTIImpl::getRegisterClassForType

[Peter Waller via Phabricator via llvm-commits]

peterwaller-arm created this revision.
Herald added subscribers: hiraditya, kristof.beyls.
Herald added a project: All.
peterwaller-arm requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

NOTE: I'm sending this for early review. Here's a possible solution to fixing
the register class issue, if it needs fixing. Another solution would be to have
`getRegUsageForType` return a tuple of (Count, Class), but this might not be
straightforward to implement for all targets, I haven't investigated.

The loop vectorizer uses `getRegisterClassForType` to determine the
register class occupied by a given an `llvm::Type*` for the purposes of
register pressure estimation, which in turn feeds into the choice of the
a maximum VF to use.

As part of this, the loop vectorizer has a heuristic
`isScalarAfterVectorization`, which `getRegisterClassForType(bool
Vector, Type *Ty)` effectively receives as its 'Vector' parameter.  The
default implementation of `getRegisterClassForType` ignores the `Type`
parameter, just returning a 'VectorRC' if Vector is True.

However, some large vector types (e.g. v128i1) are represented with a
number of scalar registers. This is known by `TLI->getRegisterType`, so
add a `TTI` interface `getRegMVTForType` and propagate this information
up to the newly implemented `getRegisterClassForType`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D125956

Files:
  llvm/include/llvm/Analysis/TargetTransformInfo.h
  llvm/include/llvm/Analysis/TargetTransformInfoImpl.h
  llvm/include/llvm/CodeGen/BasicTTIImpl.h
  llvm/lib/Analysis/TargetTransformInfo.cpp
  llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
  llvm/lib/Target/AArch64/AArch64TargetTransformInfo.h
  llvm/test/Transforms/LoopVectorize/AArch64/i1-reg-usage.ll

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D125956.430615.patch
Type: text/x-patch
Size: 5622 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220519/6ccc77f9/attachment.bin>