Some checks in isShuffleMaskLegal expect an even number of elements,
e.g. isTRN_v_undef_Mask or isUZP_v_undef_Mask, otherwise they access
invalid elements and crash. This patch adds checks to the impacted
functions.
Fixes PR41951
Reviewers: t.p.northover, dmgreen, samparker
Reviewed By: dmgreen
Differential Revision: https://reviews.llvm.org/D60690
llvm-svn: 361235
Florian Hahn