[llvm-commits] PATCH: Fix broken DAGCombiner which creates illegal vector shuffles

[Duncan Sands]

Hi Heikki,

> In current llvm-trunk there is a bug:
> If vector shuffles are not supported by the architecture but are marked to be
> expanded into extracts and builds, the dag legalization does this expand, but
> the dag combine which is done after the legalization converts these extracts and
> builds back to shuffles. This results an Cannot select error, compilelation fails.
>
> This patch adds a check which prevents this illegal combining if the
> architecture does not support shuffles.

thanks for the patch, but unfortunately it causes this test to fail:
   CodeGen/X86/avx-zext.ll
At a guess, "VT" may not be the type actually used by the shuffle.

Ciao, Duncan.