[Analysis][SVE] Improve cost model for some extending masked loads (#65957)

When performing a masked load of an unpacked SVE vector type, i.e.
nxv8i8, followed by a zero- or sign-extend to an illegal wide type
such as nxv8i32 we typically end up with a combination of an
extending masked load and pair(s) of uunpklo/hi or sunpklo/hi
instructions. For example, see test @masked_sload_8i8_8i32 in file

  CodeGen/AArch64/sve-masked-ldst-sext.ll

where

  %aval = call <vscale x 8 x i8> @llvm.masked.load.nxv8i8(...
  %aext = sext <vscale x 8 x i8> %aval to <vscale x 8 x i32>

gets lowered to

  ld1sb { z1.h }, ...
  sunpklo z0.s, z1.h
  sunpkhi z1.s, z1.h

Currently the cost for the 'sext' operation in the example above is
1, whereas this patch changes it to 2 to reflect the pair of
instructions required. Similarly, when doing a masked load of a
nxv8i8 and extending to nxv8i64 the cost is changed to 6 to reflect
the 6 unpacks required.

0 files changed, 0 insertions, 0 deletions