[PATCH] InstCombine: Recognize an unsigned mul with overflow idiom into umul.

[Benjamin Kramer]

On 19.03.2014, at 17:47, Erik Verbruggen <erik.verbruggen at me.com> wrote:

> [PATCH] InstCombine: Recognize an unsigned mul with overflow idiom into umul.
> 
>    (a*b) <u a  --> llvm.umul.with.overflow.
>    (a*b) <u b  --> llvm.umul.with.overflow.
>    a >u (a*b)  --> llvm.umul.with.overflow.
>    b >u (a*b)  --> llvm.umul.with.overflow.
> 
> This resolves a README entry and technically resolves PR4917.
> 
> <0001-InstCombine-Recognize-an-unsigned-mul-with-overflow-.patch>

The patch looks good to me. I'm just a bit nervous about feeding the backend umul.with.overflow with arbitrary integer types. Can you do some testing, esp. with strange types on a range of backends (e.g. ARM, PPC, …) so we don't get crash regressions there?

- Ben