VP intrinsics show UB if the %evl parameter is out of bounds - they must not carry the speculatable attribute. The out-of-bounds UB disappears when the %evl parameter is expanded into the mask or expansion replaces the entire VP intrinsic with non-VP code.
- Removes the speculatable attribute on all VP intrinsics.
- Generalizes the isSafeToSpeculativelyExecute function to let VP expansion know whether the VP intrinsic replacement will be speculatable. VP expansion may only discard %evl where this is the case.