COMMON_FLAGS march=native

Message

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 12:26 pm

I have gentoo installed in Parallels Desktop VM on my mac studio M1 Max, and i have a lot of issues when i set "-march=native:

COMMON_FLAGS="-march=native -O2 -pipe -fomit-frame-pointer"

how can i know, what should i put instead so it will suitable for this CPU?

alamahant · Post by **alamahant** » Tue Dec 13, 2022 12:40 pm

What kind of virtualized cpu does Parallels assign to your vm?
Safest is to omit -march= or set it to

Code: Select all

-march=x86-64

You can also run

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gcc -march=native -E -v - </dev/null 2>&1 | grep cc1

to see as what arch GCC recognizes the virt cpu.

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 12:43 pm

alamahant wrote:What kind of virtualized cpu does Parallels assign to your vm?
Safest is to omit -march= or set it to
Code: Select all
-march=x86-64

Apple M1 Max

alamahant · Post by **alamahant** » Tue Dec 13, 2022 12:48 pm

Plz check it with

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gcc -march=native -E -v - </dev/null 2>&1 | grep cc1

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 12:49 pm

alamahant wrote:Plz check it with
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gcc -march=native -E -v - </dev/null 2>&1 | grep cc1

# gcc -march=native -E -v - </dev/null 2>&1 | grep cc1
/usr/libexec/gcc/aarch64-unknown-linux-gnu/12/cc1 -E -quiet -v - -mlittle-endian -mabi=lp64 -march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth -dumpbase -

so what from this should i put in COMMON_FLAGS? the whole line as is?

alamahant · Post by **alamahant** » Tue Dec 13, 2022 12:52 pm

Better just omit -march=

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 12:53 pm

alamahant wrote:Better just omit -march=

what do you mean?

alamahant · Post by **alamahant** » Tue Dec 13, 2022 12:57 pm

In COMMON_FLAGS do not include anything "-march=xxxx"

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 12:58 pm

alamahant wrote:In COMMON_FLAGS do not include anything "-march=xxxx"

so i confused a little bit - if it will grab what it needs without -march=native, why it's required

Post by **NeddySeagoon** » Tue Dec 13, 2022 1:00 pm

leonchik1976,

The M1 is an aarch64 CPU. That's 64 bit ARM.
The

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-mlittle-endian -mabi=lp64 -march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth -dumpbase -

is what gcc uses for -march=native.

Don't use

Code: Select all

-march=x86-64

as gcc will try to output code for amd64 and fail. It will be harmless though.

What problems are you having. gcc should be OK.
clang needs version 15 to understand --march=native on your CPU

alamahant · Post by **alamahant** » Tue Dec 13, 2022 1:01 pm

The say -march=native does not work with Apple M1.
They also say clang15 does support it.
see
https://stackoverflow.com/questions/659 ... n-apple-m1
etc

Post by **NeddySeagoon** » Tue Dec 13, 2022 1:01 pm

Moved from Installing Gentoo to Gentoo on ARM.

Its one of these

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 1:02 pm

NeddySeagoon wrote:leonchik1976,

The M1 is an aarch64 CPU. That's 64 bit ARM.
The
Code: Select all
-mlittle-endian -mabi=lp64 -march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth -dumpbase -
is what gcc uses for -march=native.

Don't use
Code: Select all
-march=x86-64 
as gcc will try to output code for amd64 and fail. It will be harmless though.

What problems are you having. gcc should be OK.
clang needs version 15 to understand --march=native on your CPU

some packages can't build with -marth=native. for example - www-client/chromium.
but now - i can't even upgrade gcc - https://bugs.gentoo.org/884497

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 1:05 pm

i have clang 15
sys-devel/clang-15.0.6

Post by **NeddySeagoon** » Tue Dec 13, 2022 1:34 pm

leonchik1976,

Lets test with

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-march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth

which is what gcc detected.

That will be used by both gcc and clang.

leonchik1976 · Post by **leonchik1976** » Tue Dec 13, 2022 5:34 pm

NeddySeagoon wrote:leonchik1976,

Lets test with
Code: Select all
-march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth
which is what gcc detected.

That will be used by both gcc and clang.

NeddySeagoon, after replacing -march=native with -march=armv8-a+crypto+crc+lse+rcpc+rdma+dotprod+fp16fml+sb+ssbs+flagm+pauth,
i was able to upgrade gcc without any issue.
so - should, i revert now back to -march=native - or leave it expanded?

Post by **NeddySeagoon** » Tue Dec 13, 2022 7:01 pm

leonchik1976,

Leave it as expanded. The expanded form is what gcc claims it would do, so there should be no difference ... but one works.

Post by **NeddySeagoon** » Tue Dec 13, 2022 8:38 pm

leonchik1976,

See Gentoo Virtual Machine in the UTM App on Macbook Pro M1 Max for a better fix.
-march infers different things on amd64 and arm64.

flysideways · Post by **flysideways** » Wed Dec 14, 2022 2:23 am

https://opensource.apple.com/projects/llvm-clang/

LLVM/Clang are not gpl, but rather a modified Apache. https://llvm.org/LICENSE.txt