| Message ID | ea5ce349-0189-b7e3-0355-ed50b21d5cbb@gjlay.de |
|---|---|
| State | New |
| Headers | show |
| Series | [avr] Implement PR83737 | expand |
2018-01-08 20:19 GMT+04:00 Georg-Johann Lay <avr@gjlay.de>: > This PR skips saving of any registers in main. > > Attribute OS_main can do this as well, however we can just drop > any saves / restores in all optimized compilation -- not even > the test suite needs these saves. > > The feature can still be switched off by new -mno-OS_main > > Ok for trunk? I like it. Please commit. > > > gcc/ > Don't save registers in main(). > > PR target/83737 > * doc/invoke.texi (AVR Options) [-mOS_main]: Document it. > * config/avr/avr.opt (-mOS_main): New target option. > * config/avr/avr.c (avr_in_main_p): New static function. > (avr_regs_to_save) [avr_in_main_p]: Return 0. > (avr_prologue_setup_frame): Don't save any regs if avr_in_main_p. > (avr_expand_epilogue): Same. > * common/config/avr/avr-common.c (avr_option_optimization_table): > Switch on -mOS_main for optimizing compilations.
On 08.01.2018 18:39, Denis Chertykov wrote: > 2018-01-08 20:19 GMT+04:00 Georg-Johann Lay <avr@gjlay.de>: >> This PR skips saving of any registers in main. >> >> Attribute OS_main can do this as well, however we can just drop >> any saves / restores in all optimized compilation -- not even >> the test suite needs these saves. >> >> The feature can still be switched off by new -mno-OS_main >> >> Ok for trunk? > > I like it. > > Please commit. Committed a different approach: 1) The effect is the same as OS_task, hence named the option -mmain-is-OS_task. OS_main is too strict because that'd assume that IRQs are off when main is entered, hence due to that rare case (and when main needs a frame) OS_task is the right feature. 2) Instead of fiddling with prologue / epilogue directly, now just add OS_task to main. 3) Some restrictions have been removed re. diagnostics when naked, OS_task, OS_main are specified at the same time. Instead, the logic follows now just what the attributes are requesting (e.g. OS_main supersedes OS_task and naked supersedes OS_main). The original subject has a typo: The PR is PR83738. PR target/83738 * doc/invoke.texi (AVR Options) [-mmain-is-OS_task]: Document it. * config/avr/avr.opt (-mmain-is-OS_task): New target option. * config/avr/avr.c (avr_set_current_function): Don't error if naked, OS_task or OS_main are specified at the same time. (avr_function_ok_for_sibcall): Don't disable sibcalls for OS_task, OS_main. (avr_insert_attributes) [-mmain-is-OS_task] <main>: Add OS_task attribute. * common/config/avr/avr-common.c (avr_option_optimization_table): Switch on -mmain-is-OS_task for optimizing compilations. Index: common/config/avr/avr-common.c =================================================================== --- common/config/avr/avr-common.c (revision 256338) +++ common/config/avr/avr-common.c (working copy) @@ -31,6 +31,7 @@ static const struct default_options avr_ // a frame without need when it tries to be smart around calls. { OPT_LEVELS_ALL, OPT_fcaller_saves, NULL, 0 }, { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_mgas_isr_prologues, NULL, 1 }, + { OPT_LEVELS_1_PLUS, OPT_mmain_is_OS_task, NULL, 1 }, { OPT_LEVELS_NONE, 0, NULL, 0 } }; Index: config/avr/avr.c =================================================================== --- config/avr/avr.c (revision 256338) +++ config/avr/avr.c (working copy) @@ -1030,9 +1030,6 @@ avr_no_gccisr_function_p (tree func) static void avr_set_current_function (tree decl) { - location_t loc; - const char *isr; - if (decl == NULL_TREE || current_function_decl == NULL_TREE || current_function_decl == error_mark_node @@ -1040,7 +1037,7 @@ avr_set_current_function (tree decl) || cfun->machine->attributes_checked_p) return; - loc = DECL_SOURCE_LOCATION (decl); + location_t loc = DECL_SOURCE_LOCATION (decl); cfun->machine->is_naked = avr_naked_function_p (decl); cfun->machine->is_signal = avr_signal_function_p (decl); @@ -1049,21 +1046,19 @@ avr_set_current_function (tree decl) cfun->machine->is_OS_main = avr_OS_main_function_p (decl); cfun->machine->is_no_gccisr = avr_no_gccisr_function_p (decl); - isr = cfun->machine->is_interrupt ? "interrupt" : "signal"; + const char *isr = cfun->machine->is_interrupt ? "interrupt" : "signal"; /* Too much attributes make no sense as they request conflicting features. */ - if (cfun->machine->is_OS_task + cfun->machine->is_OS_main - + (cfun->machine->is_signal || cfun->machine->is_interrupt) > 1) - error_at (loc, "function attributes %qs, %qs and %qs are mutually" - " exclusive", "OS_task", "OS_main", isr); - - /* 'naked' will hide effects of 'OS_task' and 'OS_main'. */ - - if (cfun->machine->is_naked - && (cfun->machine->is_OS_task || cfun->machine->is_OS_main)) - warning_at (loc, OPT_Wattributes, "function attributes %qs and %qs have" - " no effect on %qs function", "OS_task", "OS_main", "naked"); + if (cfun->machine->is_OS_task + && (cfun->machine->is_signal || cfun->machine->is_interrupt)) + error_at (loc, "function attributes %qs and %qs are mutually exclusive", + "OS_task", isr); + + if (cfun->machine->is_OS_main + && (cfun->machine->is_signal || cfun->machine->is_interrupt)) + error_at (loc, "function attributes %qs and %qs are mutually exclusive", + "OS_main", isr); if (cfun->machine->is_interrupt || cfun->machine->is_signal) { @@ -3526,12 +3521,7 @@ avr_function_ok_for_sibcall (tree decl_c if (cfun->machine->is_interrupt || cfun->machine->is_signal || cfun->machine->is_naked - || avr_naked_function_p (decl_callee) - /* FIXME: For OS_task and OS_main, this might be over-conservative. */ - || (avr_OS_task_function_p (decl_callee) - != cfun->machine->is_OS_task) - || (avr_OS_main_function_p (decl_callee) - != cfun->machine->is_OS_main)) + || avr_naked_function_p (decl_callee)) { return false; } @@ -10101,13 +10091,29 @@ avr_pgm_check_var_decl (tree node) } -/* Add the section attribute if the variable is in progmem. */ +/* Implement `TARGET_INSERT_ATTRIBUTES'. */ static void avr_insert_attributes (tree node, tree *attributes) { avr_pgm_check_var_decl (node); + if (TARGET_MAIN_IS_OS_TASK + && TREE_CODE (node) == FUNCTION_DECL + && MAIN_NAME_P (DECL_NAME (node)) + // FIXME: We'd like to also test `flag_hosted' which is only + // available in the C-ish fronts, hence no such test for now. + // Instead, we test the return type of "main" which is not exactly + // the same but good enough. + && INTEGRAL_TYPE_P (TREE_TYPE (TREE_TYPE (node))) + && NULL == lookup_attribute ("OS_task", *attributes)) + { + *attributes = tree_cons (get_identifier ("OS_task"), + NULL, *attributes); + } + + /* Add the section attribute if the variable is in progmem. */ + if (TREE_CODE (node) == VAR_DECL && (TREE_STATIC (node) || DECL_EXTERNAL (node)) && avr_progmem_p (node, *attributes)) Index: config/avr/avr.opt =================================================================== --- config/avr/avr.opt (revision 256338) +++ config/avr/avr.opt (working copy) @@ -64,6 +64,10 @@ mbranch-cost= Target Report Joined RejectNegative UInteger Var(avr_branch_cost) Init(0) Set the branch costs for conditional branch instructions. Reasonable values are small, non-negative integers. The default branch cost is 0. +mmain-is-OS_task +Target Report Mask(MAIN_IS_OS_TASK) +Treat main as if it had attribute OS_task. + morder1 Target Report Undocumented Mask(ORDER_1) Index: doc/invoke.texi =================================================================== --- doc/invoke.texi (revision 256338) +++ doc/invoke.texi (working copy) @@ -669,7 +669,8 @@ -imacros @var{file} -imultilib @var{dir -mbranch-cost=@var{cost} @gol -mcall-prologues -mgas-isr-prologues -mint8 @gol -mn_flash=@var{size} -mno-interrupts @gol --mrelax -mrmw -mstrict-X -mtiny-stack -mfract-convert-truncate @gol +-mmain-is-OS_task -mrelax -mrmw -mstrict-X -mtiny-stack @gol +-mfract-convert-truncate @gol -mshort-calls -nodevicelib @gol -Waddr-space-convert -Wmisspelled-isr} @@ -16462,6 +16463,12 @@ and @code{long long} is 4 bytes. Please conform to the C standards, but it results in smaller code size. +@item -mmain-is-OS_task +@opindex mmain-is-OS_task +Do not save registers in @code{main}. The effect is similar to +attaching attribute @ref{AVR Function Attributes,,@code{OS_task}} +to @code{main}. It is activated per default if optimization is on. + @item -mn-flash=@var{num} @opindex mn-flash Assume that the flash memory has a size of
Index: common/config/avr/avr-common.c =================================================================== --- common/config/avr/avr-common.c (revision 256338) +++ common/config/avr/avr-common.c (working copy) @@ -31,6 +31,7 @@ static const struct default_options avr_ // a frame without need when it tries to be smart around calls. { OPT_LEVELS_ALL, OPT_fcaller_saves, NULL, 0 }, { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_mgas_isr_prologues, NULL, 1 }, + { OPT_LEVELS_1_PLUS, OPT_mOS_main, NULL, 1 }, { OPT_LEVELS_NONE, 0, NULL, 0 } }; Index: config/avr/avr.c =================================================================== --- config/avr/avr.c (revision 256338) +++ config/avr/avr.c (working copy) @@ -1167,6 +1167,23 @@ avr_starting_frame_offset (void) } +/* Return true if we are supposed to be in main(). This is only used + to determine if the callee-saved registers don't need to be saved + because the caller of main (crt*.o) doesn't use any of them. */ + +static bool +avr_in_main_p () +{ + return (TARGET_OS_MAIN + && MAIN_NAME_P (DECL_NAME (current_function_decl)) + // FIXME: We'd like to also test `flag_hosted' which is only + // available in the C-ish fronts, so no such test for now. + // Instead, we test the return type of "main" which is not exactly + // the same but good enough. + && INTEGRAL_TYPE_P (TREE_TYPE (TREE_TYPE (current_function_decl)))); +} + + /* Return the number of hard registers to push/pop in the prologue/epilogue of the current function, and optionally store these registers in SET. */ @@ -1180,10 +1197,11 @@ avr_regs_to_save (HARD_REG_SET *set) CLEAR_HARD_REG_SET (*set); count = 0; - /* No need to save any registers if the function never returns or - has the "OS_task" or "OS_main" attribute. */ + /* No need to save any registers if the function never returns or has the + "OS_task" or "OS_main" attribute. Dito if we are in "main". */ if (TREE_THIS_VOLATILE (current_function_decl) + || avr_in_main_p() || cfun->machine->is_OS_task || cfun->machine->is_OS_main) return 0; @@ -1651,6 +1669,7 @@ avr_prologue_setup_frame (HOST_WIDE_INT && size < size_max && live_seq && !isr_p + && !avr_in_main_p() && !cfun->machine->is_OS_task && !cfun->machine->is_OS_main && !AVR_TINY); @@ -1713,7 +1732,9 @@ avr_prologue_setup_frame (HOST_WIDE_INT emit_push_byte (reg, true); if (frame_pointer_needed - && (!(cfun->machine->is_OS_task || cfun->machine->is_OS_main))) + && (!(avr_in_main_p() + || cfun->machine->is_OS_task + || cfun->machine->is_OS_main))) { /* Push frame pointer. Always be consistent about the ordering of pushes -- epilogue_restores expects the @@ -1834,6 +1855,9 @@ avr_prologue_setup_frame (HOST_WIDE_INT if (cfun->machine->is_interrupt) irq_state = 1; + /* IRQs might be on when entering "main", hence avr_in_main_p + is *not* included in the following test. */ + if (TARGET_NO_INTERRUPTS || cfun->machine->is_signal || cfun->machine->is_OS_main) @@ -2122,6 +2146,7 @@ avr_expand_epilogue (bool sibcall_p) && !isr_p && !cfun->machine->is_OS_task && !cfun->machine->is_OS_main + && !avr_in_main_p() && !AVR_TINY); if (minimize @@ -2227,7 +2252,9 @@ avr_expand_epilogue (bool sibcall_p) } /* size != 0 */ if (frame_pointer_needed - && !(cfun->machine->is_OS_task || cfun->machine->is_OS_main)) + && !(avr_in_main_p() + || cfun->machine->is_OS_task + || cfun->machine->is_OS_main)) { /* Restore previous frame_pointer. See avr_expand_prologue for rationale for not using pophi. */ Index: config/avr/avr.opt =================================================================== --- config/avr/avr.opt (revision 256338) +++ config/avr/avr.opt (working copy) @@ -70,6 +70,10 @@ Target Report Undocumented Mask(ORDER_1) morder2 Target Report Undocumented Mask(ORDER_2) +mOS_main +Target Report Mask(OS_MAIN) +Treat main as if it had attribute OS_main. + mtiny-stack Target Report Mask(TINY_STACK) Change only the low 8 bits of the stack pointer. Index: doc/invoke.texi =================================================================== --- doc/invoke.texi (revision 256338) +++ doc/invoke.texi (working copy) @@ -669,7 +669,8 @@ -imacros @var{file} -imultilib @var{dir -mbranch-cost=@var{cost} @gol -mcall-prologues -mgas-isr-prologues -mint8 @gol -mn_flash=@var{size} -mno-interrupts @gol --mrelax -mrmw -mstrict-X -mtiny-stack -mfract-convert-truncate @gol +-mOS_main -mrelax -mrmw -mstrict-X -mtiny-stack @gol +-mfract-convert-truncate @gol -mshort-calls -nodevicelib @gol -Waddr-space-convert -Wmisspelled-isr} @@ -16472,6 +16473,12 @@ Assume that the flash memory has a size Generated code is not compatible with hardware interrupts. Code size is smaller. +@item -mOS_main +@opindex mOS_main +Do not save registers in @code{main}. The effect is similar to +attaching attribute @ref{AVR Function Attributes,,@code{OS_main}} +to @code{main}. It is activated per default if optimization is on. + @item -mrelax @opindex mrelax Try to replace @code{CALL} resp.@: @code{JMP} instruction by the shorter