On Mon, 2023-05-22 at 14:05 +0200, Richard Biener wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the > content is safe > > On Fri, May 19, 2023 at 7:58 AM <senthilkumar.selva...@microchip.com> wrote: > > On 26/04/23, 5:51 PM, "Richard Biener" <richard.guent...@gmail.com > > <mailto:richard.guent...@gmail.com>> wrote: > > > On Wed, Apr 26, 2023 at 12:56 PM <senthilkumar.selva...@microchip.com > > > <mailto:senthilkumar.selva...@microchip.com>> wrote: > > > > On Wed, Apr 26, 2023 at 3:15 PM Richard Biener via Gcc-patches > > > > <gcc-patches@gcc.gnu.org <mailto:gcc-patches@gcc.gnu.org>> wrote: > > > > > On Wed, Apr 26, 2023 at 11:42 AM Richard Biener > > > > > <richard.guent...@gmail.com <mailto:richard.guent...@gmail.com>> > > > > > wrote: > > > > > > On Wed, Apr 26, 2023 at 11:01 AM SenthilKumar.Selvaraj--- via > > > > > > Gcc-patches <gcc-patches@gcc.gnu.org > > > > > > <mailto:gcc-patches@gcc.gnu.org>> wrote: > > > > > > > Hi, > > > > > > > > > > > > > > This patch fixes PR 105523 by setting param_min_pagesize to 0 for > > > > > > > the > > > > > > > avr target. For this target, zero and offsets from zero are > > > > > > > perfectly > > > > > > > valid addresses, and the default value of param_min_pagesize ends > > > > > > > up > > > > > > > triggering warnings on valid memory accesses. > > > > > > > > > > > > I think the proper configuration is to have > > > > > > DEFAULT_ADDR_SPACE_ZERO_ADDRESS_VALID > > > > > > > > > > Err, TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID > > > > > > > > That worked. Ok for trunk and backporting to 13 and 12 branches > > > > (pending regression testing)? > > > > > > OK, but please let Denis time to comment. > > > > Didn't hear from Denis. When running regression tests with this patch, > > I found that some tests with -fdelete-null-pointer-checks were > > failing. Commit 19416210b37db0584cd0b3f3b3961324b8973d25 made > > -fdelete-null-pointer-checks false by default, while still allowing it > > to be overridden from the command line (it was previously > > unconditionally false). > > > > To keep the same behavior, I modified the hook to report zero > > addresses as valid only if -fdelete-null-pointer-checks is not set. > > With this change, all regression tests pass. > > > > Ok for trunk and backporting to 13 and 12 branches? > > I think that's bit backwards - this hook conveys more precise information > (it's address-space specific) and it is also more specific. Instead I'd > suggest to set the flag to zero in the target like nios2 or msp430 do. > In fact we should probably initialize it using this hook (and using the > default address space).
Does the below patch work? The hook impl reports that zero address is valid, and flag_delete_null_pointer_checks is set to zero if the hook says zero is a valid address. As flag_delete_null_pointer_checks is now always disabled for avr, I removed the resetting code in avr-common.cc that disables it for OPT_LEVELS_ALL by default, and added avr as a target that always keeps null pointer checks in testsuite/lib/target-supports.exp. I also removed ATTRIBUTE_UNUSED and the parameter name in the target hook to address https://gcc.gnu.org/pipermail/gcc-patches/2023-May/619014.html. PR 105523 gcc/ChangeLog: * common/config/avr/avr-common.cc: Remove setting of OPT_fdelete_null_pointer_checks. * config/avr/avr.cc (avr_option_override): Clear flag_delete_null_pointer_checks if zero_address_valid. (avr_addr_space_zero_address_valid): New function. (TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID): Provide target hook. gcc/testsuite/ChangeLog: * lib/target-supports.exp (check_effective_target_keeps_null_pointer_checks): Add avr. * gcc.target/avr/pr105523.c: New test. diff --git gcc/common/config/avr/avr-common.cc gcc/common/config/avr/avr-common.cc index 2ad0244..2f874c5 100644 --- gcc/common/config/avr/avr-common.cc +++ gcc/common/config/avr/avr-common.cc @@ -29,12 +29,6 @@ /* Implement TARGET_OPTION_OPTIMIZATION_TABLE. */ static const struct default_options avr_option_optimization_table[] = { - // With -fdelete-null-pointer-checks option, the compiler assumes - // that dereferencing of a null pointer would halt the program. - // For AVR this assumption is not true and a program can safely - // dereference null pointers. Changes made by this option may not - // work properly for AVR. So disable this option. - { OPT_LEVELS_ALL, OPT_fdelete_null_pointer_checks, NULL, 0 }, // The only effect of -fcaller-saves might be that it triggers // a frame without need when it tries to be smart around calls. { OPT_LEVELS_ALL, OPT_fcaller_saves, NULL, 0 }, diff --git gcc/config/avr/avr.cc gcc/config/avr/avr.cc index a90cade..b987837 100644 --- gcc/config/avr/avr.cc +++ gcc/config/avr/avr.cc @@ -756,6 +756,10 @@ avr_option_override (void) flag_omit_frame_pointer = 0; } + /* Disable flag_delete_null_pointer_checks if zero is a valid address. */ + if (targetm.addr_space.zero_address_valid (ADDR_SPACE_GENERIC)) + flag_delete_null_pointer_checks = 0; + if (flag_pic == 1) warning (OPT_fpic, "%<-fpic%> is not supported"); if (flag_pic == 2) @@ -9800,6 +9804,16 @@ avr_addr_space_diagnose_usage (addr_space_t as, location_t loc) (void) avr_addr_space_supported_p (as, loc); } +/* Implement `TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID. Zero is a valid + address in all address spaces. Even in ADDR_SPACE_FLASH1 etc.., + a zero address is valid and means 0x<RAMPZ val>0000, where RAMPZ is + set to the appropriate segment value. */ + +static bool +avr_addr_space_zero_address_valid (addr_space_t) +{ + return true; +} /* Look if DECL shall be placed in program memory space by means of attribute `progmem' or some address-space qualifier. @@ -14760,6 +14774,9 @@ avr_float_lib_compare_returns_bool (machine_mode mode, enum rtx_code) #undef TARGET_ADDR_SPACE_DIAGNOSE_USAGE #define TARGET_ADDR_SPACE_DIAGNOSE_USAGE avr_addr_space_diagnose_usage +#undef TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID +#define TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID avr_addr_space_zero_address_valid + #undef TARGET_MODE_DEPENDENT_ADDRESS_P #define TARGET_MODE_DEPENDENT_ADDRESS_P avr_mode_dependent_address_p diff --git gcc/testsuite/gcc.target/avr/pr105523.c gcc/testsuite/gcc.target/avr/pr105523.c new file mode 100644 index 0000000..fbbf7bf --- /dev/null +++ gcc/testsuite/gcc.target/avr/pr105523.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-Os -Wall" } */ + +/* Verify no "array subscript 0 is outside array bounds of" is generated + for accessing memory addresses in the 0-4096 range. */ + +typedef __UINT8_TYPE__ uint8_t; + +#define SREG (*(volatile uint8_t*) (0x3F + __AVR_SFR_OFFSET__ )) + +void bar (void) +{ + SREG = 0; +} diff --git gcc/testsuite/lib/target-supports.exp gcc/testsuite/lib/target-supports.exp index 263ef35..56fa73d 100644 --- gcc/testsuite/lib/target-supports.exp +++ gcc/testsuite/lib/target-supports.exp @@ -686,7 +686,8 @@ proc check_effective_target_keeps_null_pointer_checks { } { if [target_info exists keeps_null_pointer_checks] { return 1 } - if { [istarget msp430-*-*] } { + if { [istarget msp430-*-*] + || [istarget avr-*-*] } { return 1; } return 0
