[PATCH] D133955: [AArch64][CostModel] Add costs for fixed operations when using fixed vectors over SVE

[Peter Waller via Phabricator via llvm-commits]

peterwaller-arm added inline comments.


================
Comment at: llvm/test/Analysis/CostModel/AArch64/cast.ll:1035
+; FIXED-OVER-SVE2048-NEXT:  Cost Model: Found an estimated cost of 21 for instruction: %r232 = uitofp <16 x i8> undef to <16 x float>
+; FIXED-OVER-SVE2048-NEXT:  Cost Model: Found an estimated cost of 21 for instruction: %r233 = sitofp <16 x i8> undef to <16 x float>
+; FIXED-OVER-SVE2048-NEXT:  Cost Model: Found an estimated cost of 4 for instruction: %r234 = uitofp <16 x i16> undef to <16 x float>
----------------
These costs look high, consider:

  define <16 x float> @f(<16 x i8> %v) {
    %1 = sitofp <16 x i8> %v to <16 x float>
    ret <16 x float> %1
  }

The codegen I see with `llc -mtriple=aarch64 -mattr=+sve -aarch64-sve-vector-bits-min=2048`, for example:

  ptrue   p0.s, vl16
  sunpklo z0.h, z0.b
  sunpklo z0.s, z0.h
  scvtf   z0.s, p0/m, z0.s
  st1w    { z0.s }, p0, [x8]
  ret

I suspect there are more where this isn't quite right but I discovered this one by cherry picking. If I'm right, let's make sure this one is fixed and then iterate.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D133955/new/

https://reviews.llvm.org/D133955