[all-commits] [llvm/llvm-project] f46890: [RISCV] Custom type legalize i32 ISD::ABS on RV64 ...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f46890711f03dfb02722ec18dc332753967700e8
      https://github.com/llvm/llvm-project/commit/f46890711f03dfb02722ec18dc332753967700e8
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2022-02-28 (Mon, 28 Feb 2022)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVISelLowering.cpp
    M llvm/test/CodeGen/RISCV/neg-abs.ll
    M llvm/test/CodeGen/RISCV/rv64zbb.ll

  Log Message:
  -----------
  [RISCV] Custom type legalize i32 ISD::ABS on RV64 without Zbb.

Default type legalization will create sext_inreg+abs, but we may
not be able to remove the sext_inreg.

Instead this patch expands abs during type legalization to
Y = sraiw X, 31; subw(xor X, Y), Y) which doesn't require the input
to be sign extended.

This gives a big improvement for some neg-abs tests where the
abs is used more than the the neg. Previously the abs was expanded
a different way before and after type legalization. Now they are
expanded in a similar way enabling more CSE.

Reviewed By: asb

Differential Revision: https://reviews.llvm.org/D120636