[RISCV] Support `llvm.masked.compressstore` intrinsic (#83457)

The changeset enables lowering of `llvm.masked.compressstore(%data,
%ptr, %mask)` for RVV for fixed vector type into:
```
%0 = vcompress %data, %mask, %vl
%new_vl = vcpop %mask, %vl
vse %0, %ptr, %1, %new_vl
```
Such lowering is only possible when `%data` fits into available LMULs
and otherwise `llvm.masked.compressstore` is scalarized by
`ScalarizeMaskedMemIntrin` pass.
Even though RVV spec in the section `15.8` provide alternative sequence
for compressstore, use of `vcompress + vcpop` should be a proper
canonical form to lower `llvm.masked.compressstore`. If RISC-V target
find the sequence from `15.8` better, peephole optimization can
transform `vcompress + vcpop` into that sequence.

0 files changed, 0 insertions, 0 deletions