On Mon, 5 Oct 2015, Matthew Fernandez wrote:
on x86 is emitted as a call to __divdi3. If the numerator or denominator are
negative, __divdi3 negates them. If either of these values is INT64_MIN, I
believe this negation is undefined. Is this correct? If this is the case, then
it seems code like "INT64_MIN / INT64_MIN" which should be perfectly legal
accidentally causes undefined behaviour via libgcc. In practice, everything
seems to work as expected, but it seems to me that the C code of __divdi3
should not be relying on these negations working consistently.
It sounds like some casts to UDWtype should be inserted so the negation
takes place on an unsigned type.