[llvm] [RFC][IR] Support vector splats in `ConstantPointerNull` (PR #195486)

[Shilei Tian via llvm-commits]

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@@ -48,6 +48,22 @@ static cl::opt<bool> UseConstantIntForScalableSplat(
 static cl::opt<bool> UseConstantFPForScalableSplat(
     "use-constant-fp-for-scalable-splat", cl::init(true), cl::Hidden,
     cl::desc("Use ConstantFP's native scalable vector splat support."));
+static cl::opt<bool> UseConstantPtrNullForFixedLengthSplat(
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shiltian wrote:

I just made it align with the migration of ConstantInt and ConstantFP, where they are guarded by an option. @nikic said they were turned on by default just recently. This is a completely new thing so I don't think there would be any downstream uses at all, but I'm not sure if it is helpful to provide an option to turn it off.

https://github.com/llvm/llvm-project/pull/195486