Joshua Oreman
2018-09-24 23:12:19 UTC
Two functions with the same code might not be combinable during ICF if
they have different C++ exception handling metadata. PR gold/21066
demonstrates this for the case where only the LSDA differs. New
optimizations in GCC 8 can also create cases where the code is
identical but the unwind tables differ; see gold/23482 for more
details. This patch extends ICF to consider a function's associated
FDE and CIE, including any relocations therein (e.g. to the LSDA),
when deciding whether two functions are identical or not.
2018-09-24 Joshua Oreman <***@hudson-trading.com>
PR gold/21066
* gc.h (gc_process_relocs): Track relocations in .eh_frame sections
when ICF is enabled, even though the .eh_frame sections themselves
are not foldable.
* icf.cc (get_section_contents): Change arguments to permit operation
on just part of a section. Include extra identity regions in the
referring section's contents recursively.
(match_sections): Lock object here instead of in get_section_contents
so that get_section_contents can operate recursively.
(Icf::add_ehframe_links): New method.
(Icf::find_identical_sections): Pass .eh_frame sections to
add_ehframe_links(). Increase default iteration count from 2 to 3
because handling exception info typically requires one extra iteration.
* icf.h (Icf::extra_identity_list_): New data member with accessor.
(is_section_foldable_candidate): Include .gcc_except_table sections.
* options.h: Update documentation for new default ICF iteration count.
* testsuite/Makefile.am (icf_test_pr21066): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/icf_test_pr21066.cc: New source file.
* testsuite/icf_test_pr21066.sh: New test script.
they have different C++ exception handling metadata. PR gold/21066
demonstrates this for the case where only the LSDA differs. New
optimizations in GCC 8 can also create cases where the code is
identical but the unwind tables differ; see gold/23482 for more
details. This patch extends ICF to consider a function's associated
FDE and CIE, including any relocations therein (e.g. to the LSDA),
when deciding whether two functions are identical or not.
2018-09-24 Joshua Oreman <***@hudson-trading.com>
PR gold/21066
* gc.h (gc_process_relocs): Track relocations in .eh_frame sections
when ICF is enabled, even though the .eh_frame sections themselves
are not foldable.
* icf.cc (get_section_contents): Change arguments to permit operation
on just part of a section. Include extra identity regions in the
referring section's contents recursively.
(match_sections): Lock object here instead of in get_section_contents
so that get_section_contents can operate recursively.
(Icf::add_ehframe_links): New method.
(Icf::find_identical_sections): Pass .eh_frame sections to
add_ehframe_links(). Increase default iteration count from 2 to 3
because handling exception info typically requires one extra iteration.
* icf.h (Icf::extra_identity_list_): New data member with accessor.
(is_section_foldable_candidate): Include .gcc_except_table sections.
* options.h: Update documentation for new default ICF iteration count.
* testsuite/Makefile.am (icf_test_pr21066): New test case.
* testsuite/Makefile.in: Regenerate.
* testsuite/icf_test_pr21066.cc: New source file.
* testsuite/icf_test_pr21066.sh: New test script.