[llvm-commits] [PATCH] MCAssembler Performance: Lazy invalidation

[David Meyer]

This patch moves invalidation of the layout until after all relaxations have
occurred.

This prevents wasting time recomputing portions of the layout over and over.
Computing the layout is expensive, so we want to use as much of the
information generated each time as possible, instead of throwing it away
each  time a relaxation happens.

This removes a hidden O(n^2) runtime factor (where n is the number of
fragments) which causes terrifying performance problems when assembling
really large .s file with lots of relaxable instructions.

- David Meyer
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