9.2.4.7 Cleanups

Destructors for local C++ objects and similar dynamic cleanups are represented in GIMPLE by a TRY_FINALLY_EXPR. When the controlled block exits, the cleanup is run.

TRY_FINALLY_EXPR complicates the flow graph, since the cleanup needs to appear on every edge out of the controlled block; this reduces the freedom to move code across these edges. Therefore, the EH lowering pass which runs before most of the optimization passes eliminates these expressions by explicitly adding the cleanup to each edge.