https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115979
Bug ID: 115979
Summary: Implicitly generated C++ calls stop musttail search
early
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: andi-gcc at firstfloor dot org
Target Milestone: ---
(this bug requires committing the remaining pieces of musttail)
When running gcc/testsuite/g++.dg/musttail11.C with -O2 we see some "cannot
tail-call: other reasons" errors.
the problem is that find_tail_calls stops at the last call before the return.
But the C++ frontend generates destructor calls, or calls for operator int
calls after the user written tail call, which stops the search early. While
these calls cannot be tail called anyways due to the extra code they should get
a proper error message, like "code after calls". But when tree-tailcalls misses
a call only expand can print not very helpful "other reasons" error.
Possible fixes:
- When a function has f->has_musttail set but no call is found search again,
but don't stop at the first call.
- Or maybe if f->has_musttail is set just keep searching
- Or add some way for the frontend to indicate a call is generated implicitly
and can be skipped.
