Avoid visiting newly-created blocks in harden-conditionals
Reverse iteration over blocks, in gimple-harden-conditionals.cc, was
supposed to avoid visiting blocks introduced by hardening and
introducing further reversed conditionals and traps for them, but
newly-created blocks may be inserted before the current block, as
shown by the PR105455 testcase.
Use an auto_sbitmap to gather preexisting blocks that need visiting.
for gcc/ChangeLog
* gimple-harden-conditionals.cc: Include sbitmap.h.
(pass_harden_conditional_branches::execute): Skip new blocks.
(pass_harden_compares::execute): Likewise.