[all-commits] [llvm/llvm-project] 8978c1: [ARM][MVE] Tail predication conversion

[Sam Parker via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 8978c12b39f90194bb35860729ddca5e819f3b92
      https://github.com/llvm/llvm-project/commit/8978c12b39f90194bb35860729ddca5e819f3b92
  Author: Sam Parker <sam.parker at arm.com>
  Date:   2019-11-19 (Tue, 19 Nov 2019)

  Changed paths:
    M llvm/lib/Target/ARM/ARMInstrMVE.td
    M llvm/lib/Target/ARM/ARMLowOverheadLoops.cpp
    M llvm/test/CodeGen/Thumb2/LowOverheadLoops/fast-fp-loops.ll
    M llvm/test/CodeGen/Thumb2/LowOverheadLoops/mve-tail-data-types.ll
    M llvm/test/CodeGen/Thumb2/LowOverheadLoops/vector-arith-codegen.ll
    M llvm/unittests/Target/ARM/MachineInstrTest.cpp

  Log Message:
  -----------
  [ARM][MVE] Tail predication conversion

This patch modifies ARMLowOverheadLoops to convert a predicated
vector low-overhead loop into a tail-predicatd one. This is currently
a very basic conversion, with the following restrictions:
- Operates only on single block loops.
- The loop can only contain a single vctp instruction.
- No other instructions can write to the vpr.
- We only allow a subset of the mve instructions in the loop.

TODO: Pass the number of elements, not the number of iterations to
dlstp/wlstp.

Differential Revision: https://reviews.llvm.org/D69945