The special lowering for __builtin_mul_overflow introduced in r320902
fixed an ICE seen when passing mixed-sign operands to the builtin.
This patch extends the special lowering to cover mixed-width, mixed-sign
operands. In a few common scenarios, calls to muloti4 will no longer be
This should address the latest comments in PR34920 and work around the
link failure seen in:
- A/B output comparison with: https://gist.github.com/vedantk/3eb9c88f82e5c32f2e590555b4af5081