[PATCH] D120636: [RISCV] Custom type legalize i32 ISD::ABS on RV64 without Zbb.

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: asb, jrtc27, luismarques, frasercrmck.
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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D120636

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

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