Comment 4 for bug 1564156

Have discussed on IRC whether mesa should be rebuilt with llvm-3.6 as a workaround, as suggested. This is not a straight rebuild with an older toolchain; the upgrade to llvm-3.8 was needed for OpenGL 4.1 support (LP: #1535500), so this would be a behavior regression and invalidate testing since this change was made in xenial.

And that change was made in xenial at the beginning of February (Feb 9), so has been baking in xenial for 2 months without prior reports of this problem. So it seems likely that we'll be able to pin this on a later change in mesa, rather than just on llvm-3.8. This may ultimately be an llvm-3.8 bug, but we may be able to identify a smaller workaround.