[PATCH] Big-endian fix for memcpy-armv7m.S

[PATCH] Big-endian fix for memcpy-armv7m.S

[Julian Brown]

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Hi,

I noticed that memcpy-armv7m.S makes assumptions about little-endian
byte ordering that cause it to get copies with certain sizes/alignments
wrong in big-endian mode. We hit this with a "generic profile" ARMv7
big-endian multilib, but I guess anyone trying to run an M-profile chip
in big-endian mode (if such things exist) could hit the same problem.

I've tested this with (caveat, somewhat experimental!) QEMU patches:

http://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg00972.html

running under the GCC testsuite with an ARMv7 big-endian multilib, and
results show a positive delta for about 15 tests (e.g.
gcc.c-torture/execute/memcpy-2.c, gcc.c-torture/execute/pr65369.c).

OK to apply?

Thanks,

Julian

ChangeLog

    * libc/machine/arm/memcpy-armv7m.S (mis_src_copy): Handle
    big-endian mode.

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commit 45cd47548c95b13eed1eb0121ee15ca63df1b466
Author: Julian Brown <julian@codesourcery.com>
Date:   Thu Dec 8 09:56:51 2016 -0800

    Big-endian armv7m memcpy fix.
    
    In the case of memcpy-armv7m.S being built for a big-endian multilib
    (including armv7 without a specific profile), realignment code made
    assumptions about the byte ordering being little-endian.

diff --git a/newlib/libc/machine/arm/memcpy-armv7m.S b/newlib/libc/machine/arm/memcpy-armv7m.S
index 8a70c7d..c8bff36 100644
--- a/newlib/libc/machine/arm/memcpy-armv7m.S
+++ b/newlib/libc/machine/arm/memcpy-armv7m.S
@@ -265,9 +265,17 @@ memcpy:
 
 	.macro mis_src_copy shift
 1:
+#ifdef __ARM_BIG_ENDIAN
+	lsls	r4, r4, \shift
+#else
 	lsrs	r4, r4, \shift
+#endif
 	ldr	r3, [r1], #4
+#ifdef __ARM_BIG_ENDIAN
+	lsrs	r5, r3, 32-\shift
+#else
 	lsls	r5, r3, 32-\shift
+#endif
 	orr	r4, r4, r5
 	str	r4, [r0], #4
 	mov	r4, r3

Re: [PATCH] Big-endian fix for memcpy-armv7m.S

[Corinna Vinschen]

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On Dec  9 13:54, Julian Brown wrote:
> Hi,
> 
> I noticed that memcpy-armv7m.S makes assumptions about little-endian
> byte ordering that cause it to get copies with certain sizes/alignments
> wrong in big-endian mode. We hit this with a "generic profile" ARMv7
> big-endian multilib, but I guess anyone trying to run an M-profile chip
> in big-endian mode (if such things exist) could hit the same problem.
> 
> I've tested this with (caveat, somewhat experimental!) QEMU patches:
> 
> http://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg00972.html
> 
> running under the GCC testsuite with an ARMv7 big-endian multilib, and
> results show a positive delta for about 15 tests (e.g.
> gcc.c-torture/execute/memcpy-2.c, gcc.c-torture/execute/pr65369.c).
> 
> OK to apply?

Applied.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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