Implementations of type hashing.

[stuartarchibald]

As title.

[seibert]

Looks like Python 2.7 is complaining about lack of sys.hash_info and Python 3 is failing with errors like:

2019-01-22T16:39:03.8456650Z ======================================================================
2019-01-22T16:39:03.8456930Z ERROR: test_constructor (numba.tests.test_sets.TestFloatSets)
2019-01-22T16:39:03.8457950Z ----------------------------------------------------------------------
2019-01-22T16:39:03.8458020Z Traceback (most recent call last):
2019-01-22T16:39:03.8458160Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/errors.py", line 620, in new_error_context
2019-01-22T16:39:03.8458220Z     yield
2019-01-22T16:39:03.8458270Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 258, in lower_block
2019-01-22T16:39:03.8458410Z     self.lower_inst(inst)
2019-01-22T16:39:03.8458650Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 301, in lower_inst
2019-01-22T16:39:03.8458700Z     val = self.lower_assign(ty, inst)
2019-01-22T16:39:03.8458840Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 447, in lower_assign
2019-01-22T16:39:03.8458900Z     return self.lower_expr(ty, value)
2019-01-22T16:39:03.8458950Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 894, in lower_expr
2019-01-22T16:39:03.8459070Z     res = self.lower_call(resty, expr)
2019-01-22T16:39:03.8459120Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 699, in lower_call
2019-01-22T16:39:03.8459170Z     res = self._lower_call_normal(fnty, expr, signature)
2019-01-22T16:39:03.8459290Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/lowering.py", line 866, in _lower_call_normal
2019-01-22T16:39:03.8459350Z     res = impl(self.builder, argvals, self.loc)
2019-01-22T16:39:03.8459400Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/base.py", line 1132, in __call__
2019-01-22T16:39:03.8459530Z     res = self._imp(self._context, builder, self._sig, args, loc=loc)
2019-01-22T16:39:03.8459590Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/base.py", line 1157, in wrapper
2019-01-22T16:39:03.8459790Z     return fn(*args, **kwargs)
2019-01-22T16:39:03.8459930Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/setobj.py", line 1181, in set_add
2019-01-22T16:39:03.8459990Z     inst.add(item)
2019-01-22T16:39:03.8460040Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/setobj.py", line 474, in add
2019-01-22T16:39:03.8460150Z     h = get_hash_value(context, builder, self._ty.dtype, item)
2019-01-22T16:39:03.8460220Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/setobj.py", line 62, in get_hash_value
2019-01-22T16:39:03.8460260Z     fn = context.get_function(hash, sig)
2019-01-22T16:39:03.8460370Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/base.py", line 551, in get_function
2019-01-22T16:39:03.8460440Z     return self.get_function(fn, sig, _firstcall=False)
2019-01-22T16:39:03.8460500Z   File "/Users/vsts/agent/2.144.2/work/1/s/numba/targets/base.py", line 553, in get_function
2019-01-22T16:39:03.8460620Z     raise NotImplementedError("No definition for lowering %s%s" % (key, sig))
2019-01-22T16:39:03.8461190Z NotImplementedError: No definition for lowering <built-in function hash>(Literal[int](1),) -> int64

[stuartarchibald]

Python 2 problem was anticipated. Seems like the problem with sets is due to a reliance on lowering function registration ordering, I think I know at least part of the fix for this.

[sklam]

Here's my first pass review.