[Buildroot] [PATCH] toolchain/Config.in: refine BR2_TOOLCHAIN_HAS_LIBQUADMATH definition

[Thomas Perale]

In reply of:
> In commit a2380157f6688c5c065fa19060a2c33145bab95b ("toolchain: enable
> libquadmath for PowerPC with VSX"), the definition of
> BR2_TOOLCHAIN_HAS_LIBQUADMATH has been extended to also be true when
> BR2_POWERPC_CPU_HAS_VSX.
> 
> However, practical experiments show that when 64-bit VSX-capable cores
> are used in 32-bit mode, libquadmath is not built by GCC, causing
> build failures:
> 
> cp: cannot stat '/home/autobuild/autobuild/instance-3/output-1/host/powerpc-buildroot-linux-musl/lib*/libquadmath*': No such file or directory
> 
> We did an extensive testing, building the 27 combinations of:
> 
> - GCC versions: 14, 15, 16
> - C library: glibc, uclibc, musl
> - PowerPC 32-bit, PowerPC 64-bit, PowerPC 64-bit little endian
> 
> This testing provides the following results:
> 
> |      gcc14 |       powerpc64 |      glibc |         OK |
> |      gcc14 |     powerpc64le |      glibc |         OK |
> |      gcc14 |     powerpc64le |       musl |         OK |
> |      gcc14 |     powerpc64le |     uclibc |    SKIPPED |
> |      gcc14 |       powerpc64 |       musl |         OK |
> |      gcc14 |       powerpc64 |     uclibc |    SKIPPED |
> |      gcc14 |         powerpc |      glibc |     FAILED |
> |      gcc14 |         powerpc |       musl |     FAILED |
> |      gcc14 |         powerpc |     uclibc |     FAILED |
> |      gcc15 |       powerpc64 |      glibc |         OK |
> |      gcc15 |     powerpc64le |      glibc |         OK |
> |      gcc15 |     powerpc64le |       musl |         OK |
> |      gcc15 |     powerpc64le |     uclibc |    SKIPPED |
> |      gcc15 |       powerpc64 |       musl |         OK |
> |      gcc15 |       powerpc64 |     uclibc |    SKIPPED |
> |      gcc15 |         powerpc |      glibc |     FAILED |
> |      gcc15 |         powerpc |       musl |     FAILED |
> |      gcc15 |         powerpc |     uclibc |     FAILED |
> |      gcc16 |       powerpc64 |      glibc |         OK |
> |      gcc16 |     powerpc64le |      glibc |         OK |
> |      gcc16 |     powerpc64le |       musl |         OK |
> |      gcc16 |     powerpc64le |     uclibc |    SKIPPED |
> |      gcc16 |       powerpc64 |       musl |         OK |
> |      gcc16 |       powerpc64 |     uclibc |    SKIPPED |
> |      gcc16 |         powerpc |      glibc |     FAILED |
> |      gcc16 |         powerpc |       musl |     FAILED |
> |      gcc16 |         powerpc |     uclibc |     FAILED |
> 
> The "SKIPPED" are when the configuration is not possible: uClibc
> doesn't support powerpc64 or powerpc64le.
> 
> Then, as we can see, the build fails for all "powerpc"
> configuration. Our conclusion is therefore that libquadmath is not
> supported on PowerPC 32-bit. While we were not able to find direct
> evidence in the gcc code base, this practical experiment shows that is
> simply doesn't work on PowerPC 32-bit.
> 
> So, we take the logical action of adjusting
> BR2_TOOLCHAIN_HAS_LIBQUADMATH so that it is true only on
> powerpc64/powerpc64le.
> 
> Fixes:
> 
>   https://autobuild.buildroot.org/results/46d435c9f5086a8695f4f6cd4026bb0d194de13c/
> 
> Cc: Romain Naour <romain.naour at smile.fr>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni at bootlin.com>

Applied to 2025.02.x & 2026.05.x. Thanks

> ---
>  toolchain/Config.in | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/toolchain/Config.in b/toolchain/Config.in
> index 7762106bee..128f8faef2 100644
> --- a/toolchain/Config.in
> +++ b/toolchain/Config.in
> @@ -989,12 +989,12 @@ config BR2_TOOLCHAIN_HAS_ATOMIC
>  # - At least, libquadmath is available on:
>  #   - i*86
>  #   - x86_64
> -#   - PowerPC with vector scalar (VSX) instruction set
> +#   - PowerPC64 with vector scalar (VSX) instruction set
>  # - When available, libquadmath requires wchar support.
>  config BR2_TOOLCHAIN_HAS_LIBQUADMATH
>  	bool
>  	default y if BR2_i386 || BR2_x86_64
> -	default y if BR2_POWERPC_CPU_HAS_VSX
> +	default y if (BR2_powerpc64 || BR2_powerpc64le) && BR2_POWERPC_CPU_HAS_VSX
>  
>  comment "Bare metal toolchain"
>  
> -- 
> 2.55.0
> 
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