[llvm] [RISCV] Enabled masked interleaved access (PR #149981)

[Philip Reames via llvm-commits]

================
@@ -1358,7 +1358,9 @@ class LoopVectorizationCostModel {
       return;
     // Override forced styles if needed.
     // FIXME: Investigate opportunity for fixed vector factor.
+    // FIXME: Support interleave accesses.
     bool EVLIsLegal = UserIC <= 1 && IsScalableVF &&
+                      !InterleaveInfo.hasGroups() &&
----------------
preames wrote:

I was thinking about this later today, and realized I'd missed the obvious here.  While the bug is theoretically reachable through other paths, the combination of predicatation and interleave-groups currently only happens with this patch to enable the predication.  EVL without this patch can't hit this code path; I'd missed that when thinking about this earlier.

@Mel-Chen I'm tempted to just take your patch as the primary path forward here towards enabling masking interleave.  Any concerns with that?  On reflection, I don't know the splitting I'd suggested earlier is actually worthwhile.  

https://github.com/llvm/llvm-project/pull/149981