[PATCH] D97299: [IR][SVE] Add new llvm.experimental.stepvector intrinsic

[David Sherwood via Phabricator via llvm-commits]

david-arm created this revision.
david-arm added reviewers: sdesmalen, kmclaughlin, paulwalker-arm, ctetreau, fhahn.
Herald added subscribers: dexonsmith, jdoerfert, psnobl, hiraditya, kristof.beyls, tschuett.
Herald added a reviewer: efriedma.
david-arm requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

This patch adds a new llvm.experimental.stepvector intrinsic,
which takes no arguments and returns a linear integer sequence of
values of the form <0, 1, ...>. It is primarily intended for
scalable vectors, although it will work for fixed width vectors
too. It is intended that later patches will make use of this
new intrinsic when vectorising induction variables, currently only
supported for fixed width. I've added a new CreateStepVector
method to the IRBuilder, which will generate a call to this
intrinsic for scalable vectors and fall back on creating a
ConstantVector for fixed width.

For scalable vectors this intrinsic is lowered to a new ISD node
called STEP_VECTOR, which takes a single constant integer argument
as the step. During lowering this argument is set to a value of 1.
The reason for this additional argument at the codegen level is
because in future patches we will introduce various generic DAG
combines such as

  mul step_vector(1), 2 -> step_vector(2)
  add step_vector(1), step_vector(1) -> step_vector(2)
  shl step_vector(1), 1 -> step_vector(2)
  etc.

that encourage a canonical format for all targets. This hopefully
means all other targets supporting scalable vectors can benefit
from this too.

I've added cost model tests for both fixed width and scalable
vectors:

  llvm/test/Analysis/CostModel/AArch64/neon-stepvector.ll
  llvm/test/Analysis/CostModel/AArch64/sve-stepvector.ll

as well as codegen lowering tests for fixed width and scalable
vectors:

  llvm/test/CodeGen/AArch64/neon-stepvector.ll
  llvm/test/CodeGen/AArch64/sve-stepvector.ll

See this thread for discussion of the intrinsic:
https://lists.llvm.org/pipermail/llvm-dev/2021-January/147943.html


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D97299

Files:
  llvm/docs/LangRef.rst
  llvm/include/llvm/CodeGen/BasicTTIImpl.h
  llvm/include/llvm/CodeGen/ISDOpcodes.h
  llvm/include/llvm/IR/IRBuilder.h
  llvm/include/llvm/IR/Intrinsics.td
  llvm/include/llvm/Target/TargetSelectionDAG.td
  llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  llvm/lib/CodeGen/SelectionDAG/LegalizeTypes.h
  llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
  llvm/lib/IR/IRBuilder.cpp
  llvm/lib/IR/Verifier.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.h
  llvm/lib/Target/AArch64/AArch64SVEInstrInfo.td
  llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
  llvm/test/Analysis/CostModel/AArch64/neon-stepvector.ll
  llvm/test/Analysis/CostModel/AArch64/sve-stepvector.ll
  llvm/test/CodeGen/AArch64/neon-stepvector.ll
  llvm/test/CodeGen/AArch64/sve-stepvector.ll
  llvm/unittests/CodeGen/AArch64SelectionDAGTest.cpp
  llvm/unittests/IR/IRBuilderTest.cpp

-------------- next part --------------
A non-text attachment was scrubbed...
Name: D97299.325794.patch
Type: text/x-patch
Size: 39690 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20210223/577160a6/attachment.bin>