https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71937
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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Component|c++ |middle-end
--- Comment #14 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's a well-known issue in out-of-SSA as it computes liveness of SSA vars for
coalescing. We _do_ perform some coalescing even with -fno-coalesce-vars.
The solution is to not compute liveness but use SSA to query liveness as
outlined in some paper.
At some point I tried to be "optimistic" in simply assuming no conflicts for
the must-coalesce cases (abnormals) and for -O0 same SSA_NAME_VAR SSA names
quite possibly should also always coalesce successfully. So we could do
-fno-coalesce-vars a bit cheaper with the chance to eventually generate
wrong-code unnoticed.
