Hello,
I am trying to port a third-party BSP based on buildroot to yocto, but I am not
able to tune the compiler to extactly match the original one.
Particularly, if I run readelf on a binary compiled with the gcc that is used
by buildroot I get this output
ottavio@ottavio:~$ readelf -A hello_world
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A9"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3
Tag_Advanced_SIMD_arch: NEONv1
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_rounding: Needed
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: int
Tag_CPU_unaligned_access: v6
Tag_MPextension_use: Allowed
Tag_Virtualization_use: TrustZone
ottavio@ottavio:~$
I tried to replicate this by configuring a new machine, and my machine
configuration looks like this
require ../../../meta/conf/machine/include/tune-cortexa9.inc
AVAILTUNES += "cortexa9t-vfpv3-neon"
ARMPKGARCH_tune-cortexa9t-vfpv3-neon = "cortexa9"
TUNE_FEATURES_tune-cortexa9t-vfpv3-neon =
"${TUNE_FEATURES_tune-armv7at-vfpv3} neon cortexa9"
PACKAGE_EXTRA_ARCHS_tune-cortexa9t-vfpv3-neon =
"${PACKAGE_EXTRA_ARCHS_tune-armv7at-vfpv3} cortexa9-vfp cortexa9-vfpv3
cortexa9t2-vfp cortexa9t2-vfpv3 cortexa9-neon"
DEFAULTTUNE = "cortexa9t-vfpv3-neon"
If I run readelf on any compiled binary obtained with yocto, I get this result:
ottavio@ottavio:~/poky/build-xxx/tmp/work/cortexa9-vfpv3-poky-linux-gnueabi/bzip2/1.0.6-r5/build$
readelf -A .libs/bzip2
Attribute Section: aeabi
File Attributes
Tag_CPU_name: "Cortex-A9"
Tag_CPU_arch: v7
Tag_CPU_arch_profile: Application
Tag_ARM_ISA_use: Yes
Tag_THUMB_ISA_use: Thumb-2
Tag_FP_arch: VFPv3
Tag_ABI_PCS_wchar_t: 4
Tag_ABI_FP_rounding: Needed
Tag_ABI_FP_denormal: Needed
Tag_ABI_FP_exceptions: Needed
Tag_ABI_FP_number_model: IEEE 754
Tag_ABI_align_needed: 8-byte
Tag_ABI_align_preserved: 8-byte, except leaf SP
Tag_ABI_enum_size: int
Tag_CPU_unaligned_access: v6
Tag_MPextension_use: Allowed
Tag_Virtualization_use: TrustZone
ottavio@ottavio:~/poky/build-xxx/tmp/work/cortexa9-vfpv3-poky-linux-gnueabi/bzip2/1.0.6-r5/build$
I am quite close to get a similar binary, the missing part is the
Tag_Advanced_SIMD_arch: NEONv1 . I get exactly the same result if I use
DEFAULTTUNE = "cortexa9t-vfpv3", thus it seems that the neon and cortexa9-neon
options I tried to add are ignored.
At this point I have two questions
Question #1
How should I change ARMPKGARCH_tune-cortexa9t-vfpv3-neon ,
TUNE_FEATURES_tune-cortexa9t-vfpv3-neon and
PACKAGE_EXTRA_ARCHS_tune-cortexa9t-vfpv3-neon to have exactly the same kind of
elf?
Question # 2
Why the only options for neon in meta/conf/machine/include/tune-cortexa9.inc
are offered for HF tunes?
Thank you for your help
Ottavio
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