I’m trying to make a rpm tachometer. Using the lm2917 ic and I’m looking at the data sheet and it says to connect pins 1 and 11 to the negative and positive of the Schmitt comparator, do I need that circuit if I’m using a Hal sensor that would already output a square wave? If not what do I do?

 

It depends on the performance of your Hall-Sensor
and it's particular interactions with what ever it is sensing.

There is also "Noise" to be considered,
if the Hall-Sensor is remote mounted,
or in a very "Noisy" environment, like on an Engine, or a Brushed-Motor.

The Schmitt-Comparitor is never a bad idea,
it's good to have a sharp, well defined, low-Impedance, Square-Wave-Input.
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Unless there is something really strange in your circuit, it should not hurt anything to use the Schmitt trigger input, plus it will assure clean operation (within limits).