[llvm] [RISCV] Sink vp.splat operands of VP intrinsic. (PR #133245)

[Luke Lau via llvm-commits]

================
@@ -2837,39 +2837,43 @@ bool RISCVTTIImpl::isProfitableToSinkOperands(
   if (!ST->sinkSplatOperands())
     return false;
 
-  for (auto OpIdx : enumerate(I->operands())) {
-    if (!canSplatOperand(I, OpIdx.index()))
-      continue;
-
-    Instruction *Op = dyn_cast<Instruction>(OpIdx.value().get());
+  for (auto &U : I->operands()) {
+    auto *Op = dyn_cast<Instruction>(U.get());
     // Make sure we are not already sinking this operand
     if (!Op || any_of(Ops, [&](Use *U) { return U->get() == Op; }))
       continue;
 
-    // We are looking for a splat that can be sunk.
-    if (!match(Op, m_Shuffle(m_InsertElt(m_Undef(), m_Value(), m_ZeroInt()),
+    // We are looking for a splat/vp.splat that can be sunk.
+    // FIXME: Should we care about the poison value of inactive elements in
+    // vp.splat?
+    bool IsVPSplat = match(Op, m_Intrinsic<Intrinsic::experimental_vp_splat>(
+                                   m_Value(), m_Value(), m_Value()));
+    if (!IsVPSplat &&
+        !match(Op, m_Shuffle(m_InsertElt(m_Undef(), m_Value(), m_ZeroInt()),
                              m_Undef(), m_ZeroMask())))
       continue;
----------------
lukel97 wrote:

Can we match this as

```suggestion
    if (!match(Op, m_CombineOr(m_Shuffle(m_InsertElt(m_Undef(), m_Value(Val), m_ZeroInt()),
                             m_Undef(), m_ZeroMask())),
                              m_Intrinsic<Intrinsic::experimental_vp_splat>(
                                   m_Value(Val), m_Value(), m_Value())))
      continue;
```

And then below we can replace InsertElt with Val. That way it would work with both vp and non-vp splats?

https://github.com/llvm/llvm-project/pull/133245