Drop "-march=native" from HOST flags

[floppym]

GCC does not support -march=native on some targets (ia64, riscv).
The performance enhancement for makeguids isn't worth the trouble it
causes.

Bug: https://bugs.gentoo.org/831334
Signed-off-by: Mike Gilbert [email protected]

[frozencemetery]

The code you're deleting already handles ia64 correctly. I am unconvinced that the right thing is to delete it wholesale rather than adding handling for riscv.

[floppym]

What is the purpose behind passing -march=native in the first place?

[floppym]

My argument:
- HOSTCC should produce binaries that run on the build system by default, without any -march flags.
- I assume -march=native is simply there to give some performance boost. This would be a silly micro-optimization, since makeguids is a relatively simple program that runs only during the build process.

[floppym]

It looks like -march=native was added in 8134619.

A better solution now would be to not add CPPFLAGS from the environment to HOST_CPPFLAGS.

[floppym]

I added a commit to stop adding CPPFLAGS/CFLAGS to HOST_CPPFLAGS/HOST_CFLAGS.

[frozencemetery]

A better solution now would be to not add CPPFLAGS from the environment to HOST_CPPFLAGS.

I haven't thought this through fully, but I think we rely on that for package builds to inherit distro flags?

[floppym]

Distro packages can set HOST_CPPFLAGS if they really want to. It seems unimportant for a binary that only gets used during the build process and isn't installed by the resulting package.

[floppym]

Please reconsider merging this.

[asheplyakov]

It looks like -march=native was added in 8134619.

Currently makeguids is compiled with the same flags/settings as the rest
of the package, which does not work in case of cross-compiles when arch
of the build host and the target host are different.

-march=native does not influence the architecture of the binaries produced by the compiler. I.e. for GCC the target architecture is hard-coded into the binary, and for clang it can be specified by --target=arch-vendor-os-abi.

[floppym]

-march=native does not influence the architecture of the binaries produced by the compiler.

GCC does not support -march=native for all targets. For example, if you try to build efivar using a RISCV GCC toolchain, you the error demonstrated in this bug report.

gcc -O2 -pipe -mabi=lp64d -std=gnu11 -funsigned-char -fvisibility=hidden -specs=/var/tmp/portage/sys-libs/efivar-38/work/efivar-38/src/include/gcc.specs -fno-merge-constants  -std=gnu11 -funsigned-char -fvisibility=hidden -specs=/var/tmp/portage/sys-libs/efivar-38/work/efivar-38/src/include/gcc.specs -fno-merge-constants   -fPIC  -DLIBEFIVAR_VERSION=38 -D_GNU_SOURCE -I/var/tmp/portage/sys-libs/efivar-38/work/efivar-38/src/include/ -DEFIVAR_BUILD_ENVIRONMENT -march=native -c -o util.o util.c
gcc: error: ‘-march=native’: ISA string must begin with rv32 or rv64

There is no valid reason for adding -march=native to HOST_CPPFLAGS.

It also makes no sense to add CFLAGS and CPPFLAGS to HOST_CFLAGS and HOST_CPPFLAGS.

[dtor]

It looks like -march=native was added in 8134619.

Currently makeguids is compiled with the same flags/settings as the rest
of the package, which does not work in case of cross-compiles when arch
of the build host and the target host are different.

-march=native does not influence the architecture of the binaries produced by the compiler. I.e. for GCC the target architecture is hard-coded into the binary, and for clang it can be specified by --target=arch-vendor-os-abi.

I should have said "microarchitecture" not "architecture". The problem I tried to solve is that makeguids built with "-march=skylake" target that we used to build everything (not only efivars, but all packages) that is supposed to be run on a Chromebook (at that time) would trap on my workstation that had older Xeons.

[544498.193844] traps: makeguids[22888] trap invalid opcode ip:401df5 sp:7ffdc2469440 error:0 in makeguids[400000+4000]