[all-commits] [llvm/llvm-project] bf552d: [RISCV][NFC] Tests for (select (const), (const))

[Sam Elliott via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: bf552d29ee77842cae80b22e182019f7d46b183b
      https://github.com/llvm/llvm-project/commit/bf552d29ee77842cae80b22e182019f7d46b183b
  Author: Sam Elliott <selliott at lowrisc.org>
  Date:   2020-05-02 (Sat, 02 May 2020)

  Changed paths:
    A llvm/test/CodeGen/RISCV/select-const.ll

  Log Message:
  -----------
  [RISCV][NFC] Tests for (select (const), (const))

Summary:
This just adds some simple cases for testing select of constants. There will be
a follow-up patch that improves code generation in some of these cases.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D79259


  Commit: fe4245a4c1c2051adeeac7007be33bb0558143cf
      https://github.com/llvm/llvm-project/commit/fe4245a4c1c2051adeeac7007be33bb0558143cf
  Author: Sam Elliott <selliott at lowrisc.org>
  Date:   2020-05-02 (Sat, 02 May 2020)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.h
    M llvm/test/CodeGen/RISCV/select-const.ll

  Log Message:
  -----------
  [RISCV] Implement convertSelectOfConstantsToMath

Summary:
The current lowering of `select` on RISC-V uses a branch instruction to load a
register with one or other value. This is inefficient, especially in the case of
small constants that can be computed easily.

By implementing the TargetLowering::convertSelectOfConstantsToMath hook, some of
the simpler cases are covered that let us avoid introducing a branch in these
cases.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D79260


Compare: https://github.com/llvm/llvm-project/compare/a4a9a1f671ed...fe4245a4c1c2