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

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

[Waldemar Brodkorb]

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.

For uClibc-ng fenv support was enabled by commit 4c5039b80ebbe42db35af189afcff7fb7d5cace6
in Buildroot for any hard-float toolchain, so we now need to pass
-mhard-float to gcc compiler to get the predefined preprocessor macro __or1k_hard_float__,
which exposes _FPU_FPCSR_RM_MASK.

Fixes:
 - https://autobuild.buildroot.org/results/a60737adf3fdd26e8d0ae3310bef5c48716889dc

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
---
 arch/Config.in.or1k | 9 +++++++++
 package/Makefile.in | 8 ++++++++
 2 files changed, 17 insertions(+)

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
+	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
+
 # Use longcalls option for Xtensa globally.
 # The 'longcalls' option allows calls across a greater range of addresses,
 # and is required for some packages. While this option can degrade both
-- 
2.47.3

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

[Thomas Petazzoni via buildroot]

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

[Thomas Petazzoni via buildroot]

Hello,

On Sat, Aug 29, 2026 at 01:39:26PM +0200, Thomas Petazzoni wrote:

> 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?

Sorry for my mistake, but re-reading, I know understand:
BR2_OR1K_SOFT_FLOAT selects BR2_SOFT_FLOAT, and based on that uClibc
uses or doesn't use hard-float fenv stuff. That makes sense.

Still the patch seems incorrect to me, and should modify gcc.mk and
the toolchain external stuff instead.

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH] arch/or1k: fix uClibc issues with fenv enabled

[Waldemar Brodkorb]

Hello Thomas,
Thomas Petazzoni wrote,

> 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

The or1k gcc configuration has no --with-float. Only passing
-mhard-float as CFLAGS is possible.

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

[Waldemar Brodkorb]

Hi Thomas,
Thomas Petazzoni wrote,

> Hello,
> 
> On Sat, Aug 29, 2026 at 01:39:26PM +0200, Thomas Petazzoni wrote:
> 
> > 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?
> 
> Sorry for my mistake, but re-reading, I know understand:
> BR2_OR1K_SOFT_FLOAT selects BR2_SOFT_FLOAT, and based on that uClibc
> uses or doesn't use hard-float fenv stuff. That makes sense.
> 
> Still the patch seems incorrect to me, and should modify gcc.mk and
> the toolchain external stuff instead.

As I stated in my other mail --with-float is not available for gcc
on or1k. How should I proceed? How does the toolchain-wrapper
recognizes the user wants a hard-float toolchain?
For the external toolchains I understand it, but not for the
internal BR toolchains.

best regards
 Waldemar
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