https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104954
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by David Malcolm <dmalc...@gcc.gnu.org>: https://gcc.gnu.org/g:5f6197d7c197f9d2b7fb2e1a19dac39a023755e8 commit r12-7809-g5f6197d7c197f9d2b7fb2e1a19dac39a023755e8 Author: David Malcolm <dmalc...@redhat.com> Date: Thu Mar 24 20:58:10 2022 -0400 analyzer: add region::tracked_p to optimize state objects [PR104954] PR analyzer/104954 tracks that -fanalyzer was taking a very long time on a particular source file in the Linux kernel: drivers/gpu/drm/amd/display/dc/calcs/dce_calcs.c One issue occurs with the repeated use of dynamic debug lines e.g. via the DC_LOG_BANDWIDTH_CALCS macro, such as in print_bw_calcs_dceip in drivers/gpu/drm/amd/display/dc/calcs/calcs_logger.h: DC_LOG_BANDWIDTH_CALCS("#####################################################################"); DC_LOG_BANDWIDTH_CALCS("struct bw_calcs_dceip"); DC_LOG_BANDWIDTH_CALCS("#####################################################################"); [...snip dozens of lines...] DC_LOG_BANDWIDTH_CALCS("[bw_fixed] dmif_request_buffer_size: %d", bw_fixed_to_int(dceip->dmif_request_buffer_size)); When this is configured to use __dynamic_pr_debug, each of these becomes code like: do { static struct _ddebug __attribute__((__aligned__(8))) __attribute__((__section__("__dyndbg"))) __UNIQUE_ID_ddebug277 = { [...snip...] }; if (arch_static_branch(&__UNIQUE_ID_ddebug277.key, false)) __dynamic_pr_debug(&__UNIQUE_ID_ddebug277, [...the message...]); } while (0); The analyzer was naively seeing each call to __dynamic_pr_debug, noting that the __UNIQUE_ID_nnnn object escapes. At each call, as successive __UNIQUE_ID_nnnn object escapes, there are N escaped objects, and thus N need clobbering, and so we have O(N^2) clobbering of escaped objects overall, leading to huge amounts of pointless work: print_bw_calcs_data has 225 uses of DC_LOG_BANDWIDTH_CALCS, many of which are in loops. This patch adds a way to identify declarations that aren't interesting to the analyzer, so that we don't attempt to create binding_clusters for them (i.e. we don't store any state for them in our state objects). This is implemented by adding a new region::tracked_p, implemented for declarations by walking the existing IPA data the first time the analyzer sees a declaration, setting it to false for global vars that have no loads/stores/aliases, and "sufficiently safe" address-of ipa-refs. The patch gives a large speedup of -fanalyzer on the above kernel source file: Before After Total cc1 wallclock time: 180s 36s analyzer wallclock time: 162s 17s % spent in analyzer: 90% 47% gcc/analyzer/ChangeLog: PR analyzer/104954 * analyzer.opt (-fdump-analyzer-untracked): New option. * engine.cc (impl_run_checkers): Handle it. * region-model-asm.cc (region_model::on_asm_stmt): Don't attempt to clobber regions with !tracked_p (). * region-model-manager.cc (dump_untracked_region): New. (region_model_manager::dump_untracked_regions): New. (frame_region::dump_untracked_regions): New. * region-model.h (region_model_manager::dump_untracked_regions): New decl. * region.cc (ipa_ref_requires_tracking): New. (symnode_requires_tracking_p): New. (decl_region::calc_tracked_p): New. * region.h (region::tracked_p): New vfunc. (frame_region::dump_untracked_regions): New decl. (class decl_region): Note that this is also used fo SSA names. (decl_region::decl_region): Initialize m_tracked. (decl_region::tracked_p): New. (decl_region::calc_tracked_p): New decl. (decl_region::m_tracked): New. * store.cc (store::get_or_create_cluster): Assert that we don't try to create clusters for base regions that aren't trackable. (store::mark_as_escaped): Don't mark base regions that we're not tracking. gcc/ChangeLog: PR analyzer/104954 * doc/invoke.texi (Static Analyzer Options): Add -fdump-analyzer-untracked. gcc/testsuite/ChangeLog: PR analyzer/104954 * gcc.dg/analyzer/asm-x86-dyndbg-1.c: New test. * gcc.dg/analyzer/asm-x86-dyndbg-2.c: New test. * gcc.dg/analyzer/many-unused-locals.c: New test. * gcc.dg/analyzer/untracked-1.c: New test. * gcc.dg/analyzer/unused-local-1.c: New test. Signed-off-by: David Malcolm <dmalc...@redhat.com>
