[llvm-dev] RFC: Pass for lowering "non-linear" arithmetics of illegal types

[Paweł Bylica via llvm-dev]

On Tue, Oct 6, 2015 at 12:25 AM Tim Northover <t.p.northover at gmail.com>
wrote:

> On 5 October 2015 at 15:09, Paweł Bylica <llvm-dev at lists.llvm.org> wrote:
> > The pass replaces instructions mul, udiv, urem, sdiv, srem that are know
> to
> > be not supported by target's type legalization with a call to a function
> > that implements given arithmetic operation.
>
> This seems quite sensible, those functions can get bigger than you'd
> want to inline.
>
> > The pass also injects these functions to the module with a weak linkage.
> > The pass requires a function generator (interface implementation) for mul
> > and udivrem algorithms for integer types of sizes being powers of 2 (i.e.
> > i128, i256, ...). Replacements for other instructions are created using
> > these 2 algorithms.
>
> This sounds a bit weird though. It seems more natural to make these
> part of a runtime support library for your language (like compiler-rt
> is for C).
>

You are probably right. It makes more sense in general case. I was too
focused on mine. However, we can have both easily. The generator can return
either function declaration or function definition.


>
> Cheers.
>
> Tim.
>
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