Build failure on ARM <5

Build failure on ARM <5

[Reiner Herrmann]

[-- Attachment #1.1: Type: text/plain, Size: 311 bytes --]

Hi,

musl 1.1.17 fails to build [1] on arm versions <5 because
of an unsupported clz instruction.
The attached patch by Adrian Bunk [2] fixes this issue.

Kind regards,
  Reiner

[1] https://buildd.debian.org/status/fetch.php?pkg=musl&arch=armel&ver=1.1.17-1&stamp=1508450839
[2] https://bugs.debian.org/879190

[-- Attachment #1.2: 0001-CLZ-is-only-available-with-ARM-5.patch --]
[-- Type: text/x-diff, Size: 703 bytes --]

From 1e98ea50a49712931c482ca490a0ca38e0501602 Mon Sep 17 00:00:00 2001
From: Adrian Bunk <bunk@debian.org>
Date: Fri, 20 Oct 2017 20:57:23 +0200
Subject: [PATCH] CLZ is only available with ARM >= 5

---
 arch/arm/atomic_arch.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
index a121010f..c5c56f81 100644
--- a/arch/arm/atomic_arch.h
+++ b/arch/arm/atomic_arch.h
@@ -82,9 +82,13 @@ static inline void a_crash()
 		: : : "memory");
 }
 
+#if __ARM_ARCH >= 5
+
 #define a_clz_32 a_clz_32
 static inline int a_clz_32(uint32_t x)
 {
 	__asm__ ("clz %0, %1" : "=r"(x) : "r"(x));
 	return x;
 }
+
+#endif
-- 
2.15.0.rc1


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: Build failure on ARM <5

[Szabolcs Nagy]

* Reiner Herrmann <reiner@reiner-h.de> [2017-10-20 21:04:00 +0200]:
> Hi,
> 
> musl 1.1.17 fails to build [1] on arm versions <5 because
> of an unsupported clz instruction.
> The attached patch by Adrian Bunk [2] fixes this issue.
> 

this is my bug sorry,

> diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
> index a121010f..c5c56f81 100644
> --- a/arch/arm/atomic_arch.h
> +++ b/arch/arm/atomic_arch.h
> @@ -82,9 +82,13 @@ static inline void a_crash()
>  		: : : "memory");
>  }
>  
> +#if __ARM_ARCH >= 5
> +

this is not enough: v5t and v6 only supports clz in arm mode
v6t2 and v7 supports it in thumb mode too.

i think we should either check for >= 7 conservatively or check
__ARM_FEATURE_CLZ which is defined in
https://developer.arm.com/docs/ihi0053/b/arm-c-language-extensions-release-11

>  #define a_clz_32 a_clz_32
>  static inline int a_clz_32(uint32_t x)
>  {
>  	__asm__ ("clz %0, %1" : "=r"(x) : "r"(x));
>  	return x;
>  }
> +
> +#endif
> -- 
> 2.15.0.rc1
> 

Re: Build failure on ARM <5

[Rich Felker]

On Fri, Oct 20, 2017 at 09:36:45PM +0200, Szabolcs Nagy wrote:
> * Reiner Herrmann <reiner@reiner-h.de> [2017-10-20 21:04:00 +0200]:
> > Hi,
> > 
> > musl 1.1.17 fails to build [1] on arm versions <5 because
> > of an unsupported clz instruction.
> > The attached patch by Adrian Bunk [2] fixes this issue.
> > 
> 
> this is my bug sorry,
> 
> > diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
> > index a121010f..c5c56f81 100644
> > --- a/arch/arm/atomic_arch.h
> > +++ b/arch/arm/atomic_arch.h
> > @@ -82,9 +82,13 @@ static inline void a_crash()
> >  		: : : "memory");
> >  }
> >  
> > +#if __ARM_ARCH >= 5
> > +
> 
> this is not enough: v5t and v6 only supports clz in arm mode
> v6t2 and v7 supports it in thumb mode too.

I don't think this matters yet because thumb1 is not supported at all.
If we support it in the future it will matter, though.

Rich

Re: Build failure on ARM <5

[Rich Felker]

On Fri, Oct 20, 2017 at 05:26:14PM -0400, Rich Felker wrote:
> On Fri, Oct 20, 2017 at 09:36:45PM +0200, Szabolcs Nagy wrote:
> > * Reiner Herrmann <reiner@reiner-h.de> [2017-10-20 21:04:00 +0200]:
> > > Hi,
> > > 
> > > musl 1.1.17 fails to build [1] on arm versions <5 because
> > > of an unsupported clz instruction.
> > > The attached patch by Adrian Bunk [2] fixes this issue.
> > > 
> > 
> > this is my bug sorry,
> > 
> > > diff --git a/arch/arm/atomic_arch.h b/arch/arm/atomic_arch.h
> > > index a121010f..c5c56f81 100644
> > > --- a/arch/arm/atomic_arch.h
> > > +++ b/arch/arm/atomic_arch.h
> > > @@ -82,9 +82,13 @@ static inline void a_crash()
> > >  		: : : "memory");
> > >  }
> > >  
> > > +#if __ARM_ARCH >= 5
> > > +
> > 
> > this is not enough: v5t and v6 only supports clz in arm mode
> > v6t2 and v7 supports it in thumb mode too.
> 
> I don't think this matters yet because thumb1 is not supported at all.
> If we support it in the future it will matter, though.

After discussion on #musl, committed with additional notes on the
regression and limitations of the fix, and credit to the patch author.
Thanks.

Rich