As discussed in issue #37809, this transform is not safe
if the input is an undefined value.
This is similar to recent changes for urem and sdiv:
d428f09b2c99ef341ce9
There is no difference in codegen on the basic examples,
but this could lead to regressions. We may need to
improve freeze analysis or lowering if that happens.
Presumably, in real cases that are similar to the tests
where a subsequent transform removes the rem, we
will also be able to remove the freeze by seeing that
the parameter has 'noundef'.
2fa8fc3d0a