[PATCH] ARM ISel: Don't create illegal types during LowerMUL

[Jim Grosbach]

Very cool. Thanks, Arnold.

Trivial nitpick:  s/GetExtensionTo64Bits/getExtensionTo64Bits/.

Assuming Renato’s tests come back OK, this looks good to me.

-Jim

On May 14, 2013, at 12:52 PM, Arnold Schwaighofer <aschwaighofer at apple.com> wrote:

> The transformation happening here is that we want to turn a
> "mul(ext(X), ext(X))" into a "vmull(X, X)", stripping off the extension. We have
> to make sure that X still has a valid vector type - possibly recreate an
> extension to a smaller type. In case of a extload of a memory type smaller than
> 64 bit we used create a ext(load()). The problem with doing this - instead of
> recreating an extload - is that an illegal type is exposed.
> 
> This patch fixes this by creating extloads instead of ext(load()) sequences.
> 
> Fixes PR15970.
> 
> radar://13871383
> 
> From the bug report:
> 
> Initially we had a
> 
>  mul (v4i32 zextload(from v4i8), v4i32 zextload(from v4i8))
> 
> the transform should create
> 
>  vmull(v4i16 zextload(from v4i8), ...)
> 
> out of this. But instead it creates a
> 
>  vmull(v4i16 zext( v4i8 load()), ...
> 
> where an illegal type is exposed.
> 
> (This would only be exposed if this transform would run during normal legalization because vector legalization is allowed to create illegal types.)
> 
> <0001-ARM-ISel-Don-t-create-illegal-types-during-LowerMUL.patch>

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