[llvm] PreISelIntrinsicLowering: Lower llvm.exp to a loop if scalable vec arg (PR #117568)

[Stephen Long via llvm-commits]

================
@@ -335,6 +335,59 @@ bool PreISelIntrinsicLowering::expandMemIntrinsicUses(Function &F) const {
   return Changed;
 }
 
+static bool lowerExpIntrinsicToLoop(Module &M, Function &F, CallInst *CI) {
----------------
steplong wrote:

Moved it to its own file. Let me know if there's a more appropriate place. Right now, I just generalized it to unary intrinsics

https://github.com/llvm/llvm-project/pull/117568