Date: Fri, 05 Jan 2018 06:52:08 +0100 From: Jan Beich <jbeich@FreeBSD.org> To: toolchain@freebsd.org Cc: linimon@freebsd.org Subject: Is -march/-mtune=native actually supported on FreeBSD arm* or aarch64? Message-ID: <d12o-am47-wny@FreeBSD.org>
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Some ports pass -march=native and/or -mtune=native. Both are extensively documented by GCC for x86. For other architectures some excerpts say "native" is only supported on Linux (via /proc/cpuinfo). For example, $ uname -p armv6 $ echo 'int main() {}' >a.c $ clang -march=native a.c clang: error: the clang compiler does not support '-march=native' $ clang -mtune=native a.c $ pkg install -qy gcc7 $ gcc7 -march=native a.c $ gcc7 -mtune=native a.c $ uname -p aarch64 $ echo 'int main() {}' >a.c $ clang -march=native a.c clang: error: the clang compiler does not support '-march=native' $ clang -mtune=native a.c clang: error: the clang compiler does not support '-mtune=native' $ pkg install -qy gcc7 $ gcc7 -march=native a.c $ gcc7 -mtune=native a.c What's the rationale for Clang vs. GCC difference? Is it safe to run FreeBSD arm* -mtune=native binaries on CPUs older than build machine?
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