[llvm] [ConstantFold] Support scalable constant splats in ConstantFoldCastInstruction (PR #133207)

[Nikita Popov via llvm-commits]

================
@@ -160,10 +160,10 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V,
   // If the cast operand is a constant vector, perform the cast by
   // operating on each element. In the cast of bitcasts, the element
   // count may be mismatched; don't attempt to handle that here.
-  if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) &&
-      DestTy->isVectorTy() &&
-      cast<FixedVectorType>(DestTy)->getNumElements() ==
-          cast<FixedVectorType>(V->getType())->getNumElements()) {
+  if ((isa<ConstantVector, ConstantDataVector, ConstantExpr>(V)) &&
----------------
nikic wrote:

Can we drop this check entirely?

https://github.com/llvm/llvm-project/pull/133207