sheroy
Posts: 31
Joined: Fri Jun 14, 2013 5:34 pm

When compiling for Pi3 in Arch32 enabling VFP

Fri Jul 13, 2018 10:36 pm

I am using arm-none-eabi-gcc (15:5.4.1+svn241155-1) 5.4.1 20160919 to compile.


The instruction FMXR FPEXC, r0 (in my start.s file) gives the following error when compiling to enable VFP.

Error: selected processor does not support `fmxr FPEXC,r0' in ARM mode


my compiler flags are

COPS = -Wall -nostdlib -nostartfiles -ffreestanding -Iinclude -O2 \
-mcpu=cortex-a53 -mfpu=neon -mfloat-abi=hard -mfpu=crypto-neon-fp-armv8


What could be the cause for the error?

Schnoogle
Posts: 41
Joined: Sun Feb 11, 2018 4:47 pm

Re: When compiling for Pi3 in Arch32 enabling VFP

Mon Jul 16, 2018 8:47 am

Hi sheroy,

as far as 8 can see you are using the -mfpu directive twice.
I’m also using arm-none-eabi to cross compile my bare metal stuff.

I’m using this settings:
-mfpu=neon-fp-armv8 -mfloat-abi=hard -march=armv8-a

and the compiler does except and compile the fmxr instruction.

BR
Schnoogle

sheroy
Posts: 31
Joined: Fri Jun 14, 2013 5:34 pm

Re: When compiling for Pi3 in Arch32 enabling VFP

Tue Jul 17, 2018 7:24 pm

I tried I get the same error.

Schnoogle
Posts: 41
Joined: Sun Feb 11, 2018 4:47 pm

Re: When compiling for Pi3 in Arch32 enabling VFP

Tue Jul 17, 2018 7:51 pm

Hi,

well, than the issue might be your -mcpu flag set to cortex-a53 ... I’m not using this one. Instead I do -mtune=cortex-a53 together with -march=armv8-a

Hope this helps.
BR,
Schnoogle

sheroy
Posts: 31
Joined: Fri Jun 14, 2013 5:34 pm

Re: When compiling for Pi3 in Arch32 enabling VFP

Tue Jul 17, 2018 8:19 pm

last time the compiler flags were

-mfpu=neon-fp-armv8 -mfloat-abi=hard -march=armv8-a

It yet gave the same error.

AlfredJingle
Posts: 69
Joined: Thu Mar 03, 2016 10:43 pm

Re: When compiling for Pi3 in Arch32 enabling VFP

Sat Jul 21, 2018 12:23 pm

For what it is worth, I use:

Code: Select all

--no-warn -mcpu=cortex-a53+crc -mfpu=neon-vfpv4
which in my case ( I use as, not gcc ) works fine and only reports errors.
going from a 6502 on an Oric-1 to an ARMv8 is quite a big step...

Return to “Bare metal, Assembly language”

Who is online

Users browsing this forum: No registered users and 4 guests