[all-commits] [llvm/llvm-project] 8c56dd: [ARM] Stop gluing FP comparisons to FMSTAT (#116676)

[Sergei Barannikov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8c56dd3040f295874e3d5742b5dfc109adf1f728
      https://github.com/llvm/llvm-project/commit/8c56dd3040f295874e3d5742b5dfc109adf1f728
  Author: Sergei Barannikov <barannikov88 at gmail.com>
  Date:   2024-11-20 (Wed, 20 Nov 2024)

  Changed paths:
    M llvm/lib/Target/ARM/ARMISelLowering.cpp
    M llvm/lib/Target/ARM/ARMInstrVFP.td
    M llvm/lib/Target/ARM/ARMRegisterInfo.td
    M llvm/test/CodeGen/ARM/fcmp-xo.ll
    M llvm/test/CodeGen/ARM/fp16-instructions.ll
    M llvm/test/CodeGen/ARM/fp16-vminmaxnm-safe.ll
    M llvm/test/CodeGen/ARM/fptosi-sat-scalar.ll
    M llvm/test/CodeGen/ARM/fptoui-sat-scalar.ll
    M llvm/test/CodeGen/ARM/minnum-maxnum-intrinsics.ll
    M llvm/test/CodeGen/ARM/select.ll
    M llvm/test/CodeGen/Thumb2/mve-fmas.ll
    M llvm/test/CodeGen/Thumb2/mve-fptosi-sat-vector.ll
    M llvm/test/CodeGen/Thumb2/mve-fptoui-sat-vector.ll
    M llvm/test/CodeGen/Thumb2/mve-pred-ext.ll
    M llvm/test/CodeGen/Thumb2/mve-vcmpf.ll
    M llvm/test/CodeGen/Thumb2/mve-vcmpfr.ll
    M llvm/test/CodeGen/Thumb2/mve-vcmpfz.ll

  Log Message:
  -----------
  [ARM] Stop gluing FP comparisons to FMSTAT (#116676)

Following #116547, this changes the result of `ARMISD::CMPFP*` and the
operand of `ARMISD::FMSTAT` from a special `Glue` type to a normal type.

This change allows comparisons to be CSEd and scheduled around as can be
seen in the test changes.

Note that `ARMISD::FMSTAT` is still glued to its consumer nodes; this is
going to be changed in a separate patch.

This patch also sets `CopyCost` of `cl_FPSCR_NZCV` register class to a
negative value. The reason is the same as for CCR register class: it
makes DAG scheduler and InstrEmitter try to avoid copies of `FPCSR_NZCV`
register to / from virtual registers. Previously, this was not
necessary, since no attempt was made to create copies in the first
place.

There might be a case when a copy can't be avoided (although not found
in existing tests). If a copy is necessary, the virtual register will be
created with `cl_FPSCR_NZCV` register class. If this register class is
inappropriate, `TRI::getCrossCopyRegClass` should be modified to return
the correct class.

Pull Request: https://github.com/llvm/llvm-project/pull/116676



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