[TableGen] Use SmallMapVector to simplify some code that was trying to keep a vector unique
Summary:
This code previously had a SmallVector of std::pairs containing an unsigned and another SmallVector. The outer vector was using the unsigned effectively as a key to decide which SmallVector to add into. So each time something new needed to be added the out vector needed to be scanned. If it wasn't found a new entry needed to be added to be added. This sounds very much like a map, but the next loop iterates over the outer vector to get a deterministic order.
We can simplify this code greatly if use SmallMapVector instead. This uses more stack space since we now have a vector and a map, but the searching and creating new entries all happens behind the scenes. It should also make the search more efficient though usually there are only a few entries so that doesn't matter much.
We could probably get determinism by just using std::map which would iterate over the unsigned key, but that would generate different output from what we get with the current implementation.
Reviewers: RKSimon, dblaikie
Reviewed By: dblaikie
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D44711
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328070 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed