[LLVMdev] 8-bit DIV IR irregularities

[Eli Friedman]

On Wed, Jun 27, 2012 at 4:02 PM, Nowicki, Tyler <tyler.nowicki at intel.com> wrote:
> Hi,
>
>
>
> I noticed that when dividing with signed 8-bit values the IR uses a 32-bit
> signed divide, however, when unsigned 8-bit values are used the IR uses an
> 8-bit unsigned divide. Why not use a 8-bit signed divide when using 8-bit
> signed values?

"sdiv i8 -128, -1" has undefined behavior; "sdiv i32 -128, -1" is well-defined.

-Eli