[llvm] [RISCV][TTI] Cost a subvector extract at a register boundary with exact vlen (PR #82405)

[Luke Lau via llvm-commits]

================
@@ -436,6 +436,22 @@ InstructionCost RISCVTTIImpl::getShuffleCost(TTI::ShuffleKind Kind,
     if (Index == 0)
       return TTI::TCC_Free;
 
+    // If we're extracting a subvector of at most m1 size at a sub-register
+    // boundary - which unfortunately we need exact vlen to identity - this is
----------------
lukel97 wrote:

```suggestion
    // boundary - which unfortunately we need exact vlen to identify - this is
```

https://github.com/llvm/llvm-project/pull/82405