[PATCH] D133464: [WIP][BPF] Add sext load instructions

[Yonghong Song via Phabricator via llvm-commits]

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Add sign-extension load instructions.

For kernel bpf selftest pyperf180, the number of
instructions without this patch is 91472. With this
patch, the number of instructions is 80652. Most improvements
come from

  r1 = *(u32 *)(r8 + 12) 
  r1 <<= 32
  r1 s>>= 32

to

  r1 = *(s32 *)(r8 + 12) 

Such a new instruction not only improves bpf code, but 
can also improve jitted code since most architecture
has explicit sign extension insntructions.

To-Do list:

- put the new functionality into e.g, -mcpu=v4
- implement the linux kernel part to support the new insn


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D133464

Files:
  llvm/lib/Target/BPF/BPFISelLowering.cpp
  llvm/lib/Target/BPF/BPFInstrFormats.td
  llvm/lib/Target/BPF/BPFInstrInfo.td
  llvm/lib/Target/BPF/Disassembler/BPFDisassembler.cpp
  llvm/test/CodeGen/BPF/sext.ll

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