RTEMS not compiling with -mfloat-abi=hard in ARM926ejs

[Sebastian Huber]

On 04/01/2019 20:52, Amarnath MB wrote:
> Hi,
>
> I'm working on RTEMS 5.0 BSP for a new SOC based on ARM926EJS which 
> hasaVFP9-S Floating point coprocessor inside.
> I was able to successfully boot RTEMS and run hello.exe and ticker.exe 
> testsuite samples using u-boot.
>
> Ihave enabled VFP from Uboot using the coprocessor instructions given 
> in ARM926EJS RM.
> In order to use the VFP coprocessor in RTEMS I have added
> *CPU_CFLAGS = -mcpu=arm926ej-s -mthumb -mfloat-abi=hard *in the .cfg 
> file for the BSP.
> But during the BSP build, it gives error "configure: error: C compiler 
> cannot create executables".
> How can I enable hard float support in my BSP?
> *
> *
> *As a trial, I have built BSP with *CPU_CFLAGS = -mcpu=arm926ej-s 
> -mthumb* and manually added***
> **
> **CPU_CFLAGS = -mcpu=arm926ej-s -mthumb -mfloat-abi=hard* in the 
> makefile (Makefile.leaf) for application build.*
> *In this case, I'm getting error 'error: o-optimize/init.o uses VFP 
> register arguments, o-optimize/rtems-app.exe does not'*
> ***
> *

You try to link objects with incompatible ABIs together and the linker 
is kind enough to let you not do this. You have to make sure that all 
your objects are compiled with the right combination of machine flags.

> *As per RTEMS CPU Architecture Supplement Release 5.0.0 (master) 
> Section 3.1.3 Floating Point Unit only*
> *VFPv3-D32, **VFPv3-D16 and **FPv4-SP-D16*are supported by RTEMS*, but 
> VFP9-S Floating point coprocessor is an
> *
> *implementation of the /Vector Floating-point Architecture/ (VFPv2) 
> which is not listed in 3.1.3.
> *
> *Does this state that VFP9-S Floating point coprocessor is not 
> supported by RTEMS?*

This section was out of date. I updated it:

https://docs.rtems.org/branches/master/cpu-supplement/arm.html#multilibs

> *
> *
> *For your info floating point operations are working fine in the 
> application built using ***-mfloat-abi=soft**.**
> **
> **
> **Thanks in advance for all your precious time.
> **
> **
> **
> **Regards,
> * *
>
> **
>
> *Amarnath MB***
>
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Sebastian Huber, embedded brains GmbH

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