Code Review - Fix gcc-fuggetaboud-ecx issue V2

[Davide Libenzi]

Adding RSI, RDI, ECX as clobbers does not work. But marking them RW does.

https://github.com/brho/akaros/compare/master...dlibenzi:gcc_fuggetaboud_ecx_v2

The following changes since commit 2fa42319139e4cc5ca853546363f84443d0ead00:

  Rename 'reallocarray' to 'kreallocarray'. (2015-11-25 18:02:04 -0500)

are available in the git repository at:

  g...@github.com:dlibenzi/akaros gcc_fuggetaboud_ecx_v2

for you to fetch changes up to 3d4a4ec56106e29a31265eed30db6d77cf0bfc53:

  Flags RSI, RDI, ECX as RW operands so that GCC does not assume const (2015-12-09 19:55:47 -0800)

----------------------------------------------------------------

Davide Libenzi (1):

      Flags RSI, RDI, ECX as RW operands so that GCC does not assume const

 kern/arch/x86/uaccess.h | 4 ++--

 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kern/arch/x86/uaccess.h b/kern/arch/x86/uaccess.h

index cba0ef5..f8edaf4 100644

--- a/kern/arch/x86/uaccess.h

+++ b/kern/arch/x86/uaccess.h

@@ -101,8 +101,8 @@ struct extable_ip_fixup {

  " jmp 2b\n" \

  ".previous\n" \

  _ASM_EXTABLE(1b, 3b) \

- : "=r"(err) \

- : "D" (dst), "S" (src), "c" (count), "i" (errret), "0" (err) \

+ : "=r"(err), "+D" (dst), "+S" (src), "+c" (count) \

+ : "i" (errret), "0" (err) \

  : "memory")

 

 static inline int __put_user(void *dst, const void *src, unsigned int count)

[barret rhoden]

On 2015-12-09 at 20:04 'Davide Libenzi' via Akaros wrote:
> Adding RSI, RDI, ECX as clobbers does not work. But marking them RW
> does.

yep! that's what i was aiming for. =) will try it out tomorrow.

barret

[Davide Libenzi]

I tested that in your branch. Works.
Also looked at generated code, which now has proper reload.

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[Davide Libenzi]

I added a CLD in there as well. For zero cycles, it's a good peace of mind.

[Barret Rhoden]

On 2015-12-10 at 05:35 "'Davide Libenzi' via Akaros"

<aka...@googlegroups.com> wrote:
> I added a CLD in there as well. For zero cycles, it's a good peace of
> mind.

it shouldn't be necessary, since we CLD on our entry points. but i'll
take the peace of mind. =)

[Barret Rhoden]

Thanks,

Merged to master at 495a723da7db..3f805ed22943 (from, to]

You can see the entire diff with 'git diff' or at
https://github.com/brho/akaros/compare/495a723da7db...3f805ed22943

On 2015-12-09 at 20:04 "'Davide Libenzi' via Akaros"