[llvm] [LV] Support binary and unary operations with EVL-vectorization (PR #93854)

[Florian Hahn via llvm-commits]

================
@@ -1405,6 +1407,62 @@ void VPlanTransforms::addActiveLaneMask(
     HeaderMask->replaceAllUsesWith(LaneMask);
 }
 
+/// Replace recipes with their EVL variants.
+static void transformRecipestoEVLRecipes(VPlan &Plan, VPValue &EVL) {
+  SmallVector<VPValue *> HeaderMasks = collectAllHeaderMasks(Plan);
+  for (VPValue *HeaderMask : collectAllHeaderMasks(Plan)) {
+    for (VPUser *U : collectUsersRecursively(HeaderMask)) {
+      auto *CurRecipe = dyn_cast<VPRecipeBase>(U);
+      if (!CurRecipe)
+        continue;
+      auto GetNewMask = [&](VPValue *OrigMask) -> VPValue * {
+        assert(OrigMask && "Unmasked recipe when folding tail");
+        return HeaderMask == OrigMask ? nullptr : OrigMask;
+      };
+
+      VPRecipeBase *NewRecipe =
+          TypeSwitch<VPRecipeBase *, VPRecipeBase *>(CurRecipe)
+              .Case<VPWidenLoadRecipe>([&](VPWidenLoadRecipe *L) {
+                VPValue *NewMask = GetNewMask(L->getMask());
+                return new VPWidenLoadEVLRecipe(*L, EVL, NewMask);
+              })
+              .Case<VPWidenStoreRecipe>([&](VPWidenStoreRecipe *S) {
+                VPValue *NewMask = GetNewMask(S->getMask());
+                return new VPWidenStoreEVLRecipe(*S, EVL, NewMask);
+              })
+              .Case<VPWidenRecipe>([&](VPWidenRecipe *W) -> VPRecipeBase * {
+                unsigned Opcode = W->getOpcode();
+                if (!Instruction::isBinaryOp(Opcode) &&
+                    !Instruction::isUnaryOp(Opcode))
+                  return nullptr;
+                return new VPWidenEVLRecipe(W, EVL);
+              })
+              .Case<VPReductionRecipe>([&](VPReductionRecipe *Red) {
+                return new VPReductionEVLRecipe(*Red, EVL,
+                                                GetNewMask(Red->getCondOp()));
+              })
+              .Default([&](VPRecipeBase *R) { return nullptr; });
+
+      if (NewRecipe) {
----------------
fhahn wrote:

nit
```suggestion
      if (!NewRecipe) 
        continue;
```
to reduce indent below

https://github.com/llvm/llvm-project/pull/93854