Use uniforms set to populate VecValuesToIgnore.

For instructions in uniform set, they will not have vector versions so
add them to VecValuesToIgnore.
For induction vars, those only used in uniform instructions or consecutive
ptrs instructions have already been added to VecValuesToIgnore above. For
those induction vars which are only used in uniform instructions or
non-consecutive/non-gather scatter ptr instructions, the related phi and
update will also be added into VecValuesToIgnore set.

The change will make the vector RegUsages estimation less conservative.

Differential Revision: https://reviews.llvm.org/D20474

llvm-svn: 275912