[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #25 from CVS Commits --- The master branch has been updated by Richard Biener : https://gcc.gnu.org/g:c6ef9d8d3f11221df1ea6358b8d4e79e42f074fb commit r11-2455-gc6ef9d8d3f11221df1ea6358b8d4e79e42f074fb Author: Richard Biener Date: Thu Jul 30 11:46:43 2020 +0200 debug/96383 - emit debug info for used external functions This makes sure to emit full declaration DIEs including formal parameters for used external functions. This helps debugging when debug information of the external entity is not available and also helps external tools cross-checking ABI compatibility which was the bug reporters use case. For cc1 this affects debug information size as follows: VM SIZE FILE SIZE ++ GROWING ++ [ = ] 0 .debug_info +1.63Mi +1.3% [ = ] 0 .debug_str +263Ki +3.4% [ = ] 0 .debug_abbrev +101Ki +4.9% [ = ] 0 .debug_line +5.71Ki +0.0% +44% +16 [Unmapped]+48 +1.2% -- SHRINKING -- [ = ] 0 .debug_loc -213 -0.0% -0.0% -48 .text -48 -0.0% [ = ] 0 .debug_ranges -16 -0.0% -0.0% -32 TOTAL +1.99Mi +0.6% and DWARF compression via DWZ can only shave off minor bits here. Previously we emitted no DIEs for external functions at all unless they were referenced via DW_TAG_GNU_call_site which for some GCC revs caused a regular DIE to appear and since GCC 4.9 only a stub without formal parameters. This means at -O0 we did not emit any DIE for external functions but with optimization we emitted stubs. 2020-07-30 Richard Biener PR debug/96383 * langhooks-def.h (lhd_finalize_early_debug): Declare. (LANG_HOOKS_FINALIZE_EARLY_DEBUG): Define. (LANG_HOOKS_INITIALIZER): Amend. * langhooks.c: Include cgraph.h and debug.h. (lhd_finalize_early_debug): Default implementation from former code in finalize_compilation_unit. * langhooks.h (lang_hooks::finalize_early_debug): Add. * cgraphunit.c (symbol_table::finalize_compilation_unit): Call the finalize_early_debug langhook. gcc/c-family/ * c-common.h (c_common_finalize_early_debug): Declare. * c-common.c: Include debug.h. (c_common_finalize_early_debug): finalize_early_debug langhook implementation generating debug for extern declarations. gcc/c/ * c-objc-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG): Define to c_common_finalize_early_debug. gcc/cp/ * cp-objcp-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG): Define to c_common_finalize_early_debug. gcc/testsuite/ * gcc.dg/debug/dwarf2/pr96383-1.c: New testcase. * gcc.dg/debug/dwarf2/pr96383-2.c: Likewise. libstdc++-v3/ * testsuite/20_util/assume_aligned/3.cc: Use -g0.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #24 from rguenther at suse dot de --- On Fri, 31 Jul 2020, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 > > --- Comment #23 from Jakub Jelinek --- > I guess one question is what will e.g. LTO do when merging a DECL_IGNORED > DECL_EXTERNAL FUNCTION_DECL with !DECL_IGNORED definition. And also what other side effects the flag has, like no GNU_call_site tags for a call to such function maybe? Who knows. I'm posting the langhook variant now
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #23 from Jakub Jelinek --- I guess one question is what will e.g. LTO do when merging a DECL_IGNORED DECL_EXTERNAL FUNCTION_DECL with !DECL_IGNORED definition.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #22 from Eric Botcazou --- On the other hand, if all it takes to avoid the new DIEs is to set the DECL_IGNORED_P flag, then it might be simpler to go ahead with the change and set the flag in Ada more often.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #21 from rguenther at suse dot de --- On Fri, 31 Jul 2020, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 > > --- Comment #20 from Jakub Jelinek --- > lang_hooks.finalize_early_debug_info ? > In the default definition move there just the > /* Emit early debug for reachable functions, and by consequence, > locally scoped symbols. */ > struct cgraph_node *cnode; > FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (cnode) > (*debug_hooks->early_global_decl) (cnode->decl); > and for c-family do what you were testing? Hmm, works for me I guess.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #20 from Jakub Jelinek --- lang_hooks.finalize_early_debug_info ? In the default definition move there just the /* Emit early debug for reachable functions, and by consequence, locally scoped symbols. */ struct cgraph_node *cnode; FOR_EACH_FUNCTION_WITH_GIMPLE_BODY (cnode) (*debug_hooks->early_global_decl) (cnode->decl); and for c-family do what you were testing?
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #19 from rguenther at suse dot de --- On Fri, 31 Jul 2020, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 > > --- Comment #18 from Jakub Jelinek --- > (In reply to rguent...@suse.de from comment #17) > > Well, not sure - FEs do quite a good job with unused warnings by > > simply tracking things with TREE_USED so I guess global extern decls > > can be tracked as used/unused as well by FEs and what is a use > > (and worth emitting debug for) may be better decided by the FE, > > say for offsetof (X, m) we maybe want debug info for X even if it > > is not otherwise used? > > Perhaps for C, but for C++ with thousands of inline functions everywhere > pretty > much everything is TREE_USED. True... So we could add lang_hooks.finalize_fndecl_referenced_from_final_symboltable () with the default implementation registering debug for nodes with bodies and for C/C++ override this to also register debug for externals? Not sure if we should hand it the cgraph node or whether FEs should figure out whether it is an alias or thunk in their own representation. Ada could leave it as default or do nothing in it. We need a better name though. Not sure if we need to ever do sth else from that hook and thus make it sepecific for debug emission...
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #18 from Jakub Jelinek --- (In reply to rguent...@suse.de from comment #17) > Well, not sure - FEs do quite a good job with unused warnings by > simply tracking things with TREE_USED so I guess global extern decls > can be tracked as used/unused as well by FEs and what is a use > (and worth emitting debug for) may be better decided by the FE, > say for offsetof (X, m) we maybe want debug info for X even if it > is not otherwise used? Perhaps for C, but for C++ with thousands of inline functions everywhere pretty much everything is TREE_USED.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #17 from rguenther at suse dot de --- On Fri, 31 Jul 2020, jakub at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 > > --- Comment #15 from Jakub Jelinek --- > Unless we want for C/C++ to emit DW_AT_external DIEs for all function > prototypes that appear in the TU, we need ME help, because only there we > analyze the callgraph and prune cgraph nodes that are unreachable. Well, not sure - FEs do quite a good job with unused warnings by simply tracking things with TREE_USED so I guess global extern decls can be tracked as used/unused as well by FEs and what is a use (and worth emitting debug for) may be better decided by the FE, say for offsetof (X, m) we maybe want debug info for X even if it is not otherwise used?
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #16 from Eric Botcazou --- > So, for Ada, would you like to preserve current behavior rather than what > Richard's patch does? > If so, can't we have a langhook that decides that? > I don't know much about Ada, but would think that having the prototypes even > for functions defined in other shared libraries if they are called or > referenced in the TU is useful even for Ada. This yields useless duplication in 99.99% of the cases though and the debug info is already large enough. Can't you do this from the front-end instead, for the c-family of compilers?
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #15 from Jakub Jelinek --- Unless we want for C/C++ to emit DW_AT_external DIEs for all function prototypes that appear in the TU, we need ME help, because only there we analyze the callgraph and prune cgraph nodes that are unreachable.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #14 from Richard Biener --- (In reply to Jakub Jelinek from comment #13) > (In reply to Eric Botcazou from comment #12) > > > So with the attached 'updated patch' I see > > > > > > === gnat tests === > > > > > > > > > Running target unix/ > > > FAIL: gnat.dg/debug11_pkg.adb scan-assembler-not foreign_imported_func > > > FAIL: gnat.dg/debug9.adb scan-assembler-times (DIE > > > (0x[a-f0-9]*) > > > DW_ > > > TAG_type_unit) 0 > > > > > > where the first FAIL seems obvious from the name of > > > 'foreign_imported_func' > > > and the changed outcome is expected and OK? > > > > The annoying thing is the discrepancy with the variable case; in other > > words, the patch is undercutting gnat_write_global_declarations > > (utils.c:5913). Ah, indeed. > So, for Ada, would you like to preserve current behavior rather than what > Richard's patch does? > If so, can't we have a langhook that decides that? > I don't know much about Ada, but would think that having the prototypes even > for functions defined in other shared libraries if they are called or > referenced in the TU is useful even for Ada. I think that we need that loop in cgraphunit.c at all shows that frontends are not enough in control... The middle-end cannot really make the best decision on what declarations are worth emitting debug info for so what Ada does looks best here and maybe other FEs should follow suit... Note that Ada does this even when -fsyntax-only (if it supports that). I don't remember exactly but I think we've chosen to emit function DIEs during unit finalization instead of at rest_of_decl_compilation time because of ordering issues (FEs call rest_of_decl_compilation very much too often...). The most simplistic langhook would be to ask the FE whether a specific decl should get debug info (but we have DECL_IGNORED for this already ...?).
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #13 from Jakub Jelinek --- (In reply to Eric Botcazou from comment #12) > > So with the attached 'updated patch' I see > > > > === gnat tests === > > > > > > Running target unix/ > > FAIL: gnat.dg/debug11_pkg.adb scan-assembler-not foreign_imported_func > > FAIL: gnat.dg/debug9.adb scan-assembler-times (DIE (0x[a-f0-9]*) > > DW_ > > TAG_type_unit) 0 > > > > where the first FAIL seems obvious from the name of 'foreign_imported_func' > > and the changed outcome is expected and OK? > > The annoying thing is the discrepancy with the variable case; in other > words, the patch is undercutting gnat_write_global_declarations > (utils.c:5913). So, for Ada, would you like to preserve current behavior rather than what Richard's patch does? If so, can't we have a langhook that decides that? I don't know much about Ada, but would think that having the prototypes even for functions defined in other shared libraries if they are called or referenced in the TU is useful even for Ada.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #12 from Eric Botcazou --- > So with the attached 'updated patch' I see > > === gnat tests === > > > Running target unix/ > FAIL: gnat.dg/debug11_pkg.adb scan-assembler-not foreign_imported_func > FAIL: gnat.dg/debug9.adb scan-assembler-times (DIE (0x[a-f0-9]*) > DW_ > TAG_type_unit) 0 > > where the first FAIL seems obvious from the name of 'foreign_imported_func' > and the changed outcome is expected and OK? The annoying thing is the discrepancy with the variable case; in other words, the patch is undercutting gnat_write_global_declarations (utils.c:5913). > For the second FAIL I see type units for system__secondary_stack_* types > and the extra subroutines are likely the invoked system__secondary_stack_* > functions like > > <1><77>: Abbrev Number: 38 (DW_TAG_subprogram) > <78> DW_AT_external: 1 > <78> DW_AT_name: (indirect string, offset: 0x47): > system__secondar > y_stack__ss_release > <7c> DW_AT_decl_file : 2 > <7d> DW_AT_decl_line : 95 > <7e> DW_AT_decl_column : 14 > <7f> DW_AT_sibling : <0x8e> > <2><83>: Abbrev Number: 39 (DW_TAG_formal_parameter) > <84> DW_AT_name: m > <86> DW_AT_decl_file : 2 > <87> DW_AT_decl_line : 95 > <88> DW_AT_decl_column : 26 > <89> DW_AT_type: <0x8e> > <2><8d>: Abbrev Number: 0 > > note they are not DECL_ARTIFICIAL and also not DECL_IGNORED. Now the > testcase tries to test sth else than no type units at all as its > comment explains. Yes, I agree that there is probably a missing DECL_IGNORED here.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 Richard Biener changed: What|Removed |Added CC||ebotcazou at gcc dot gnu.org --- Comment #11 from Richard Biener --- So with the attached 'updated patch' I see === gnat tests === Running target unix/ FAIL: gnat.dg/debug11_pkg.adb scan-assembler-not foreign_imported_func FAIL: gnat.dg/debug9.adb scan-assembler-times (DIE (0x[a-f0-9]*) DW_ TAG_type_unit) 0 where the first FAIL seems obvious from the name of 'foreign_imported_func' and the changed outcome is expected and OK? For the second FAIL I see type units for system__secondary_stack_* types and the extra subroutines are likely the invoked system__secondary_stack_* functions like <1><77>: Abbrev Number: 38 (DW_TAG_subprogram) <78> DW_AT_external: 1 <78> DW_AT_name: (indirect string, offset: 0x47): system__secondar y_stack__ss_release <7c> DW_AT_decl_file : 2 <7d> DW_AT_decl_line : 95 <7e> DW_AT_decl_column : 14 <7f> DW_AT_sibling : <0x8e> <2><83>: Abbrev Number: 39 (DW_TAG_formal_parameter) <84> DW_AT_name: m <86> DW_AT_decl_file : 2 <87> DW_AT_decl_line : 95 <88> DW_AT_decl_column : 26 <89> DW_AT_type: <0x8e> <2><8d>: Abbrev Number: 0 note they are not DECL_ARTIFICIAL and also not DECL_IGNORED. Now the testcase tries to test sth else than no type units at all as its comment explains.
[Bug debug/96383] [8/9/10/11 Regression] Full ABI information missing from GCC compiled C
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96383 --- Comment #10 from Richard Biener --- Created attachment 48960 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48960=edit updated patch Avoid aliases and thunks, avoid not declared builtins w/o body. Updates stats for cc1 to FILE SIZEVM SIZE -- -- +1.0% +1.21Mi [ = ] 0.debug_info +4.4% +92.0Ki [ = ] 0.debug_abbrev +0.1% +6.76Ki [ = ] 0.debug_str +0.0% +5.80Ki [ = ] 0.debug_line +0.0%+426 [ = ] 0.debug_loc +0.0%+144 [ = ] 0.debug_ranges +0.0% +80 +0.0% +80.text +0.0% +52 [ = ] 0.strtab +0.0% +32 +0.0% +32.rodata +0.0% +24 [ = ] 0.symtab +0.0% +16 +0.0% +16.eh_frame +0.0% +8 +0.0% +8.eh_frame_hdr -1.9%-138 [ = ] 0[Unmapped] +0.4% +1.31Mi +0.0%+136TOTAL and after applying DWZ to both: FILE SIZEVM SIZE -- -- +1.0% +751Ki [ = ] 0.debug_info +4.8% +87.8Ki [ = ] 0.debug_abbrev +0.1% +6.76Ki [ = ] 0.debug_str +0.0% +5.80Ki [ = ] 0.debug_line +0.0%+426 [ = ] 0.debug_loc +0.0%+144 [ = ] 0.debug_ranges +0.0% +80 +0.0% +80.text +0.0% +52 [ = ] 0.strtab +0.0% +32 +0.0% +32.rodata +0.0% +24 [ = ] 0.symtab +0.0% +16 +0.0% +16.eh_frame +0.0% +8 +0.0% +8.eh_frame_hdr -1.9%-137 [ = ] 0[Unmapped] +0.3% +852Ki +0.0%+136TOTAL
