on 2022/8/29 14:35, Kewen.Lin via Gcc-patches wrote: > on 2022/8/15 16:33, Kewen.Lin via Gcc-patches wrote: >> on 2022/7/11 11:42, Kewen.Lin wrote: >>> on 2022/6/15 14:20, Kewen.Lin wrote: >>>> Hi Honza, >>>> >>>> Thanks for the comments! Some replies are inlined below. >>>> >>>> on 2022/6/14 19:37, Jan Hubicka wrote: >>>>>> Hi, >>>>>> >>>>>> Function optimize_function_for_size_p returns OPTIMIZE_SIZE_NO >>>>>> if func->decl is not null but no cgraph node is available for it. >>>>>> As PR105818 shows, this could give unexpected result. For the >>>>>> case in PR105818, when parsing bar decl in function foo, the cfun >>>>>> is a function structure for foo, for which there is none cgraph >>>>>> node, so it returns OPTIMIZE_SIZE_NO. But it's incorrect since >>>>>> the context is to optimize for size, the flag optimize_size is >>>>>> true. >>>>>> >>>>>> The patch is to make optimize_function_for_size_p to check >>>>>> optimize_size as what it does when func->decl is unavailable. >>>>>> >>>>>> One regression failure got exposed on aarch64-linux-gnu: >>>>>> >>>>>> PASS->FAIL: gcc.dg/guality/pr54693-2.c -Os \ >>>>>> -DPREVENT_OPTIMIZATION line 21 x == 10 - i >>>>>> >>>>>> The difference comes from the macro LOGICAL_OP_NON_SHORT_CIRCUIT >>>>>> used in function fold_range_test during c parsing, it uses >>>>>> optimize_function_for_speed_p which is equal to the invertion >>>>>> of optimize_function_for_size_p. At that time cfun->decl is valid >>>>>> but no cgraph node for it, w/o this patch function >>>>>> optimize_function_for_speed_p returns true eventually, while it >>>>>> returns false with this patch. Since the command line option -Os >>>>>> is specified, there is no reason to interpret it as "for speed". >>>>>> I think this failure is expected and adjust the test case >>>>>> accordingly. >>>>>> >>>>>> Is it ok for trunk? >>>>>> >>>>>> BR, >>>>>> Kewen >>>>>> ----- >>>>>> >>>>>> PR target/105818 >>>>>> >>>>>> gcc/ChangeLog: >>>>>> >>>>>> * predict.cc (optimize_function_for_size_p): Check optimize_size when >>>>>> func->decl is valid but its cgraph node is unavailable. >>>>>> >>>>>> gcc/testsuite/ChangeLog: >>>>>> >>>>>> * gcc.target/powerpc/pr105818.c: New test. >>>>>> * gcc.dg/guality/pr54693-2.c: Adjust for aarch64. >>>>>> --- >>>>>> gcc/predict.cc | 2 +- >>>>>> gcc/testsuite/gcc.dg/guality/pr54693-2.c | 2 +- >>>>>> gcc/testsuite/gcc.target/powerpc/pr105818.c | 9 +++++++++ >>>>>> 3 files changed, 11 insertions(+), 2 deletions(-) >>>>>> create mode 100644 gcc/testsuite/gcc.target/powerpc/pr105818.c >>>>>> >>>>>> diff --git a/gcc/predict.cc b/gcc/predict.cc >>>>>> index 5734e4c8516..6c60a973236 100644 >>>>>> --- a/gcc/predict.cc >>>>>> +++ b/gcc/predict.cc >>>>>> @@ -268,7 +268,7 @@ optimize_function_for_size_p (struct function *fun) >>>>>> cgraph_node *n = cgraph_node::get (fun->decl); >>>>>> if (n) >>>>>> return n->optimize_for_size_p (); >>>>>> - return OPTIMIZE_SIZE_NO; >>>>>> + return optimize_size ? OPTIMIZE_SIZE_MAX : OPTIMIZE_SIZE_NO; >>>>> >>>>> We could also do (opt_for_fn (cfun->decl, optimize_size) that is >>>>> probably better since one can change optimize_size with optimization >>>>> attribute. >>>> >>>> Good point, agree! >>>> >>>>> However I think in most cases we check for optimize_size early I think >>>>> we are doing something wrong, since at that time htere is no profile >>>>> available. Why exactly PR105818 hits the flag change issue? >>>> >>>> For PR105818, the reason why the flag changs is that: >>>> >>>> Firstly, the inconsistent flag is OPTION_MASK_SAVE_TOC_INDIRECT bit >>>> of rs6000_isa_flags_explicit, it's set as below: >>>> >>>> /* If we can shrink-wrap the TOC register save separately, then use >>>> -msave-toc-indirect unless explicitly disabled. */ >>>> if ((rs6000_isa_flags_explicit & OPTION_MASK_SAVE_TOC_INDIRECT) == 0 >>>> && flag_shrink_wrap_separate >>>> && optimize_function_for_speed_p (cfun)) >>>> rs6000_isa_flags |= OPTION_MASK_SAVE_TOC_INDIRECT; >>>> >>>> Initially, rs6000 initialize target_option_default_node with >>>> OPTION_MASK_SAVE_TOC_INDIRECT unset, at that time cfun is NULL >>>> and optimize_size is true. >>>> >>>> Later, when c parser handling function foo, it builds target >>>> option node as target_option_default_node in function >>>> handle_optimize_attribute, it does global option saving and >>>> verifying there as well, at that time the cfun is NULL, no >>>> issue is found. And function store_parm_decls allocates >>>> struct_function for foo then, cfun becomes function struct >>>> for foo, when c parser continues to handle the decl bar in >>>> foo, function handle_optimize_attribute works as before, >>>> tries to restore the target options at the end, it calls >>>> targetm.target_option.restore (rs6000_function_specific_restore) >>>> which calls function rs6000_option_override_internal again, >>>> at this time the cfun is not NULL while there is no cgraph >>>> node for its decl, optimize_function_for_speed_p returns true >>>> and gets the OPTION_MASK_SAVE_TOC_INDIRECT bit of flag >>>> rs6000_isa_flags set unexpectedly. It becomes inconsistent >>>> as the one saved previously. >>>> >>>> IMHO, both contexts of global and function decl foo here hold >>>> optimize_size, function optimize_function_for_speed_p should >>>> not return true anyway. >>>> >>>> btw, the aarch64 failed case also gets the unexpected >>>> result for optimize_function_for_speed_p during c parsing >>>> (fold_range_test <- ... <- c_parser_condition). >>>> >>>> IIUC, in parsing time we don't have the profile information >>>> available. >>>> >>> >>> Hi Honza, >>> >>> Does the above explanation sound reasonable to you? >>>
Hi Honza, Gentle ping^4 ... BR, Kewen