New issue 1921: Problematic introduction of promote in presence of int switches
https://bitbucket.org/pypy/pypy/issue/1921/problematic-introduction-of-promote-in
Carl Friedrich Bolz:
The following code lead to very confusing behaviour on Pycket recently:
```
#!python
from rpython.rtyper.raisingops import int_floordiv_ovf
...
if y == 0:
raise SchemeException("zero_divisor")
try:
res = int_floordiv_ovf(x, y) # misnomer, should be int_truncdiv or
so
except OverflowError:
return
self.arith_quotient(values.W_Bignum(rbigint.fromint(other.value)))
```
(we were intentionally using int_floordiv_ovf, to get the C integer division
behaviour). What happened was that int_floordiv_ovf was inlined. That function
starts with ``if y == -1: ...``. The two conditions on y were turned into a
switch, which lead to the JIT introducing a promote just before it. This is
clearly nonsense.
How do we solve this? do the if-to-switch conversion before inlining? require
an explicit promote before switches where that is safe (probably breaks some
existing code)?
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