[llvm-exegesis] Refactor how forbidden registers are computed.
Summary:
Right now latency generation can incorrectly select the scratch register
as a dependency-carrying register.
- Move the logic for preventing register selection from Uops
implementation to common SnippetGenerator class.
- Aliasing detection now takes a set of forbidden registers just like
random register assignment does.
Reviewers: gchatelet
Subscribers: tschuett, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D68084
llvm-svn: 373048