[PATCH] D129957: [RISCV] Add isel patterns for ineg+setge/le/uge/ule.

[Craig Topper via Phabricator via llvm-commits]

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setge/le/uge/ule selected by themselves require an xori with 1.
If we're negating the setcc, we can fold the xori with the neg
to create an addi with -1.

This works because xori X, 1 is equivalent to 1 - X if X is either
0 or 1. So we're doing -(1 - X) which is X-1 or X+-1.

This improves the code for selecting between 0 and -1 based on a
condition for some conditions.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129957

Files:
  llvm/lib/Target/RISCV/RISCVInstrInfo.td
  llvm/test/CodeGen/RISCV/select-const.ll

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