[llvm] SLP/RISCV: add test for vectorized ctpop, like in X86 (PR #65330)

[Simon Pilgrim via llvm-commits]

================
@@ -0,0 +1,107 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
+; RUN: opt < %s -passes=slp-vectorizer -S -mtriple=riscv64 -mattr=+v,+f | FileCheck %s
----------------
RKSimon wrote:

I don't know much about riscv, but maybe similar RUNs as found in the rvv/fixed-vectors-ctpop.ll codegen tests?

https://github.com/llvm/llvm-project/pull/65330