[llvm] [RISCV][CG]Use processShuffleMasks for per-register shuffles (PR #120803)

[Philip Reames via llvm-commits]

================
@@ -168,12 +168,11 @@ define <4 x i64> @m2_splat_into_slide_two_source_v2_lo(<4 x i64> %v1, <4 x i64>
 define <4 x i64> @m2_splat_into_slide_two_source(<4 x i64> %v1, <4 x i64> %v2) vscale_range(2,2) {
 ; CHECK-LABEL: m2_splat_into_slide_two_source:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    vsetivli zero, 1, e8, mf8, ta, ma
----------------
preames wrote:

Did I miss a separate commit which added additional testing for this change?  It clearly isn't NFC, and the test changes here seem fairly minimal for something this involved.  If not, please commit additional coverage (including the cause of the functional bug) before reapplying.  

https://github.com/llvm/llvm-project/pull/120803