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nagmat84
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Joined: 27 Mar 2007
Posts: 218
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 Posted: Tue Apr 02, 2024 8:32 pm Post subject: CFLAGS for chroot-build with incompatible CPU types |
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I try to set up a build server for my old laptop following the guide https://wiki.gentoo.org/wiki/Binary_package_guide#Handling_.2AFLAGS_in_detail. My laptop is a Lenovo X1 Carbon 3rd Gen. My future build server is based on an AMD EPYC 7702P. Currently, I try to figure out what CFLAGS I can/should use such that the binary packages from the build server also run on the laptop.
resolve-march-native gives | Code: |
Build server: -march=znver2 -mno-mwaitx -mno-xsaves --param=l1-cache-line-size=64 --param=l1-cache-size=64 --param=l2-cache-size=512
Client (laptop): -march=broadwell -mabm -maes --param=l1-cache-line-size=64 --param=l1-cache-size=32 --param=l2-cache-size=3072 |
cpuid2cpuflags gives | Code: |
Build server: CPU_FLAGS_X86: aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt rdrand sha sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3
Client (laptop): CPU_FLAGS_X86: aes avx avx2 f16c fma3 mmx mmxext pclmul popcnt rdrand sse sse2 sse3 sse4_1 sse4_2 ssse3 |
(indentation by myself for easier comparison.)
According, to https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html the CPU types Broadwell and Zen v2 are incompatible (neither is a superset of the other).
Instruction set extensions supported by both CPU types:- ABM
- ADCX
- AES
- AVX
- AVX2
- BMI
- BMI2
- CX16
- F16C
- FMA
- FSGSBASE
- MMX
- MOVBE
- PCLMUL
- POPCNT
- RDSEED
- SSE
- SSE2
- SSE3
- SSE4.1
- SSE4.2
- SSSE3
Instruction set extensions only supported by Broadwell:- FXSR
- HLE
- LZCNT
- PREFETCHW
- RDRND
- SAHF
- XSAVE
Instruction set extensions only supported by Zen v2:- CLFLUSHOPT
- CLWB
- CLZERO
- RDPID
- SHA
- SSE4A
- WBNOINVD
- XSAVEC
(At least this is how I understand that manual page.) From what I understand, a safe, conservative selection for CFLAGS would be | Code: | | CFLAGS="-march=x86-64 -mtune=broadwell" |
However, I wonder if I should at least add the instruction set extensions which have both CPU types in common, i.e. whether | Code: | | CFLAGS="-march=x86-64 -mtune=broadwell -mabm -maes -mavx -mavx2 -mbmi -mbmi2 -mcx16 -mf16c -mfma -mfsgsbase -mmmx -mmovbe -mpclmul -mpopcnt -mrdseed -msse -msse2 -mssse3 -msse4.1 -msse4.2 -msse3" |
would provide any benefits.- Would it work?
- Does it improve anything?
Last edited by nagmat84 on Wed Apr 03, 2024 3:07 pm; edited 1 time in total |
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netfab
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Joined: 03 Mar 2005
Posts: 1902
Location: 127.0.0.1
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| Posted: Wed Apr 03, 2024 7:26 am Post subject: |
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Hi,
Yes, I think you should.
Somewhere in the gcc manual you can find :
| Quote: |
There is no -march=generic option because -march indicates the instruction set the compiler can use, and there is no
generic instruction set applicable to all processors.
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Since you want to use -march=x86-64 you should add instructions you want to enable. |
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