[PATCH] D71636: [AArch64][SVE][WIP] Add support for vscale constants (?)

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.
efriedma added reviewers: sdesmalen, huntergr, c-rhodes, cameron.mcinally, simoll, hfinkel, rkruppe, greened, rengolin, lattner.
Herald added subscribers: psnobl, hiraditya, kristof.beyls, tschuett.
Herald added a project: LLVM.

This patch allows the following IR to compile:

  define i32 @vscale() {
    ret i32 ptrtoint (<vscale x 1 x i8>* getelementptr (<vscale x 1 x
  i8>, <vscale x 1 x i8>* null, i64 1) to i32)
  }

to the following, which produces a value equal to the runtime value of vscale:

  cntd    x8
  lsr     x0, x8, #1
                                  // kill: def $w0 killed $w0 killed $x0
  ret

Posting this patch mainly to pose the question of whether the input IR is supposed to be valid.  Some people have expressed the opinion that vscale should not be an llvm::Constant.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71636

Files:
  llvm/include/llvm/CodeGen/ISDOpcodes.h
  llvm/lib/Analysis/ConstantFolding.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.h

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