Add Check about negative uint constant

[haoyang9804]

Focusing the problem in here.
As the author said, when we negative after ones_like a uint variable, tvm crashes as expected. But negative a uint const would run smoothly. So I tried the following script, only changing relay.var to relay.const, which should crash but not.

importtvmfromtvmimportrelayvar_7=relay.const(1, dtype="uint64")
var_10=relay.ones_like(var_7)
y=relay.negative(var_10)
F=relay.Function([], y)
mod=tvm.IRModule()
mod['main'] =Fprint(mod)
graph, lib, params=relay.build(mod, target='llvm') # crash

I have make the following change to the codebase:
In TryConstFold<tir::Sub>, which is needed for negative operator, I add a check about potential negative uint value: If minuend is of uint and it's value is 0 while the subtrahend is of uint, then the difference would be negative and of uint. This situation should be forbidden.

[haoyang9804]

Could any reviewer help take a look about why my commit fails in sanity check? I do not have adequate experience in commiting fixes. Thanks in advance. cc @junrushao1994@jroesch

[leeexyz]

@haoyang9804 You can find the Sanity Check Log here.

change

[2022-03-04T06:18:11.419Z] - ICHECK(!(pa && pa->dtype.is_uint() && pa->value == 0U && b.dtype().is_uint())) << \
[2022-03-04T06:18:11.419Z] - "Checked failed. Minuend 's value is 0U and it's dtype is uint " << \
[2022-03-04T06:18:11.419Z] - "while Subtrahend's dtype is uint; which will cause a negative unit";

to

[2022-03-04T06:18:11.419Z] + ICHECK(!(pa && pa->dtype.is_uint() && pa->value == 0U && b.dtype().is_uint()))
[2022-03-04T06:18:11.419Z] + << "Checked failed. Minuend 's value is 0U and it's dtype is uint "
[2022-03-04T06:18:11.419Z] + << "while Subtrahend's dtype is uint; which will cause a negative uint";

You'd better run the check locally before sending a PR.

bash ./tests/scripts/task_lint.sh

[haoyang9804]

[haoyang9804]

@leeexyz Thanks for you kind reply. Though I cannot run this lint script locally due to inaccessibility of some files. But finally it works after I change the format of the code.
BTW, could you please help check my commit? I am not sure whether or not my fix violates some principles of TVM

[haoyang9804]

Hi @masahi. Would you mind to take a look at this pr. Maybe it's a small problem, but I think it shows an inconsistency between uint const and uint var.