[llvm-exegesis] Ignore instructions using custom inserter

Some instructions defined in table-gen files sets usesCustomInserter
bit, which means it has to be lowered by target code and isn't actually
valid instruction at MC level. So we should treat them like pseudo
instructions.

Reviewed By: gchatelet

Differential Revision: https://reviews.llvm.org/D94898

GitOrigin-RevId: 9d2f06445ffaceb501abd9477d3b5ce7231af49d
3 files changed