Nikita Popov 492a4a428f [APInt] Fix 1-bit edge case in smul_ov() ...

The sdiv used to check for overflow can itself overflow if the
LHS is signed min and the RHS is -1. The code tried to account for
this by also checking the commuted version. However, for 1-bit
values, signed min and -1 are the same value, so both divisions
overflow. As such, the overflow for -1 * -1 was not detected
(which results in -1 rather than 1 for 1-bit values). Fix this by
explicitly checking for this case instead.

Noticed while adding exhaustive test coverage for smul_ov(),
which is also part of this commit.

2021-10-16 20:31:04 +02:00

96 KiB

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