[msan] Only check shadow memory for operands that are sized.

Fixes PR33347: https://bugs.llvm.org/show_bug.cgi?id=33347.

Differential Revision: https://reviews.llvm.org/D35160

Patch by Matt Morehouse.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@307684 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed