[llvm-branch-commits] [llvm] [LV][REVEC] Initial support for re-vectorisation (PR #208213)

[Gaëtan Bossu via llvm-branch-commits]

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@@ -14,19 +14,40 @@
 
 namespace llvm {
 
-/// A helper function for converting Scalar types to vector types. If
+/// A helper function for converting scalar or vector types to vector types. If
 /// the incoming type is void, we return void. If the EC represents a
-/// scalar, we return the scalar type.
+/// scalar, we return the input type. For vector inputs, the existing vector
+/// element count is multiplied by EC.
 inline Type *toVectorTy(Type *Scalar, ElementCount EC) {
   if (Scalar->isVoidTy() || Scalar->isMetadataTy() || EC.isScalar())
     return Scalar;
+  if (auto *VTy = dyn_cast<VectorType>(Scalar)) {
+    assert(!(VTy->getElementCount().isScalable() && EC.isScalable()) &&
+           "Attempt to create <vscale x vscale x N x elt>!");
+
+    if (auto *FVTy = dyn_cast<FixedVectorType>(VTy))
+      return VectorType::get(VTy->getElementType(),
+                             EC * FVTy->getNumElements());
+
+    return VectorType::get(VTy->getElementType(),
+                           VTy->getElementCount() * EC.getKnownMinValue());
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gbossu wrote:

I wanted to keep the helper generic, but for REVEC this isn't a scenario we can trigger. I can simplify that case away if you prefer 🙂 

https://github.com/llvm/llvm-project/pull/208213