Re: [Buildroot] [PATCH] arch/or1k: fix uClibc issues with fenv enabled

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

Hello Waldemar,

On Thu, Aug 20, 2026 at 12:15:58AM +0200, Waldemar Brodkorb wrote:
> OpenRISC architecture can be either soft-float or hard-float, so add the
> ability to the user to configure it.
> 
> GNU libc has hard-float support since 03 May 2024, see here:
> https://sourceware.org/pipermail/glibc-cvs/2024q2/085211.html
> There fenv functions f.e. were added to glibc.
> 
> uClibc-ng has added fenv functions in commit 8a77b4785acd143d76ccc08142abb39c0100de3d
> on 27 April 2025.
> 
> musl does not have any or1k architecture specific fenv support.
> 
> Tested with all 6 combinations of C libraries and float configurations.

Are you sure? I don't see how your patch solves the soft-float
configuration.

> diff --git a/arch/Config.in.or1k b/arch/Config.in.or1k
> index f42aef9eef..e626907496 100644
> --- a/arch/Config.in.or1k
> +++ b/arch/Config.in.or1k
> @@ -1,3 +1,12 @@
> +config BR2_OR1K_SOFT_FLOAT
> +	bool "Use soft-float"
> +	select BR2_SOFT_FLOAT

This should be "default y", to preserve existing behavior.

> +	help
> +	  If your target CPU does not have a Floating Point Unit (FPU)
> +	  or a kernel FPU emulator, but you still wish to support
> +	  floating point functions, then everything will need to be
> +	  compiled with soft floating point support (-msoft-float).
> +
>  config BR2_ARCH
>  	default "or1k"
>  
> diff --git a/package/Makefile.in b/package/Makefile.in
> index eac28b3a96..69859e8ce4 100644
> --- a/package/Makefile.in
> +++ b/package/Makefile.in
> @@ -106,6 +106,14 @@ TARGET_ABI += -mabi=spe -mfloat-gprs=double -Wa,-me500mc
>  endif
>  endif
>  
> +# use hard-float option globally for OpenRISC, when not
> +# soft-float choosen by the user.
> +ifeq ($(BR2_or1k),y)
> +ifneq ($(BR2_OR1K_SOFT_FLOAT),y)
> +TARGET_ABI += -mhard-float
> +endif
> +endif

This needs somehow to go in the toolchain wrapper, so instead of your
change, you would need something like this:

diff --git a/package/gcc/gcc.mk b/package/gcc/gcc.mk
index 180e90856d..16c9e08ba5 100644
--- a/package/gcc/gcc.mk
+++ b/package/gcc/gcc.mk
@@ -212,6 +212,10 @@ ifeq ($(BR2_SOFT_FLOAT),y)
 ifeq ($(BR2_arm)$(BR2_armeb)$(BR2_mips)$(BR2_mipsel)$(BR2_mips64)$(BR2_mips64el)$(BR2_powerpc)$(BR2_sparc),y)
 HOST_GCC_COMMON_CONF_OPTS += --with-float=soft
 endif
+else
+ifeq ($(BR2_or1k),y)
+HOST_GCC_COMMON_CONF_OPTS += --with-float=hard
+endif
 endif
 
 # Determine arch/tune/abi/cpu options
diff --git a/toolchain/toolchain-external/pkg-toolchain-external.mk b/toolchain/toolchain-external/pkg-toolchain-external.mk
index 270cf814ed..a9593a4a69 100644
--- a/toolchain/toolchain-external/pkg-toolchain-external.mk
+++ b/toolchain/toolchain-external/pkg-toolchain-external.mk
@@ -243,6 +243,9 @@ TOOLCHAIN_EXTERNAL_CFLAGS += $(call qstrip,$(BR2_TARGET_OPTIMIZATION))
 ifeq ($(BR2_SOFT_FLOAT),y)
 TOOLCHAIN_EXTERNAL_CFLAGS += -msoft-float
 TOOLCHAIN_EXTERNAL_TOOLCHAIN_WRAPPER_ARGS += -DBR_SOFTFLOAT=1
+else ifeq ($(BR2_or1k),y)
+TOOLCHAIN_EXTERNAL_CFLAGS += -mhard-float
+TOOLCHAIN_EXTERNAL_TOOLCHAIN_WRAPPER_ARGS += -DBR_HARDFLOAT=1
 endif
 
 TOOLCHAIN_EXTERNAL_TOOLCHAIN_WRAPPER_ARGS += \
diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c
index 5b306190bb..7dba652e28 100644
--- a/toolchain/toolchain-wrapper.c
+++ b/toolchain/toolchain-wrapper.c
@@ -61,6 +61,9 @@ static char *predef_args[] = {
 #ifdef BR_SOFTFLOAT
        "-msoft-float",
 #endif /* BR_SOFTFLOAT */
+#ifdef BR_HARDFLOAT
+       "-mhard-float",
+#endif /* BR_HARDFLOAT */
 #ifdef BR_SIMD
        "-msimd=" BR_SIMD,
 #endif

But more importantly, I don't see how your patch fixes the soft float
situation. My understanding is that soft-float is the default on
OR1K. Your patch doesn't change *anything* in soft-float
configuration, it only passes -mhard-float in hard float
configurations, and makes hard float the default.

How can your patch fix anything with BR2_OR1K_SOFT_FLOAT enabled?

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
_______________________________________________
buildroot mailing list
buildroot@buildroot.org
https://lists.buildroot.org/mailman/listinfo/buildroot