I'm in need of some expert advise about CFLAGS. I'm going to install Gentoo in two systems, an Atom 330 and a P4 prescott. Since compiling lots of stuff in an Atom is less than joyful, I intend to do almost all compilation on the prescott and produce binary packages to use on the Atom. So, something like CFLAGS="-march=native ..." is out. I know I could set CFLAGS="-march=i686 -O2 -pipe -fomit-frame-pointer", but I would like to extract a bit more juice from the hw, while still keeping stable systems. So, I thought of setting CFLAGS for both systems as -march=i686, plus the flags that are pulled by -march=native in both systems, plus some other flags:
-march=i686 -mno-aes -mno-pclmul -mno-popcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mno-avx -mno-avx2 -mno-sse4.2 -mno-sse4.1 -mno-lzcnt -mno-rdrnd -mno-f16c -mno-fsgsbase --param l1-cache-size=16 --param l1-cache-line-size=64 --param l2-cache-size=1024 -pni -mtrr This is what is pulled by -march=native, using gcc -march=native -E -v - </dev/null 2>&1 | grep cc1 Prescott: -march=prescott -mno-cx16 -mno-sahf -mno-movbe -mno-aes -mno-pclmul -mno-popcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mno-avx -mno-avx2 -mno-sse4.2 -mno-sse4.1 -mno-lzcnt -mno-rdrnd -mno-f16c -mno-fsgsbase --param l1-cache-size=16 --param l1-cache-line-size=64 --param l2-cache-size=1024 -mtune=prescott Atom: -march=atom -mcx16 -msahf -mmovbe -mno-aes -mno-pclmul -mno-popcnt -mno-abm -mno-lwp -mno-fma -mno-fma4 -mno-xop -mno-bmi -mno-bmi2 -mno-tbm -mno-avx -mno-avx2 -mno-sse4.2 -mno-sse4.1 -mno-lzcnt -mno-rdrnd -mno-f16c -mno-fsgsbase --param l1-cache-size=24 --param l1-cache-line-size=64 --param l2-cache-size=512 -mtune=atom Flags supported (from cat /proc/cpuinfo|grep flags): Prescott: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc pebs bts pni dtes64 monitor ds_cpl cid xtpr Atom: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl tm2 ssse3 cx16 xtpr pdcm movbe lahf_lm dtherm Some questions: 1) Is this strategy right? If so, any other flags to add? (or any flags to remove from the list?) 2) The --param flags are the ones of the computer that will do the compiling. I'm guessing the produced binaries are compatible with cpu with different --param flags. Is this right? TIA Jorge Almeida
