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 ... BR, Kewen
