Pull in r280837 from upstream llvm trunk (by Wei Mi):
Don't reduce the width of vector mul if the target doesn't support SSE2. The patch is to fix PR30298, which is caused by rL272694. The solution is to bail out if the target has no SSE2. Differential Revision: https://reviews.llvm.org/D24288
This fixes building the multimedia/libx264 port on i386.