[PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[Ramsay Jones]

On Intel machines, the msvc compiler defines the CPU architecture
macros _M_IX86 and _M_X64 (equivalent to __i386__ and __x86_64__
respectively). Use these macros in the pre-processor expression
to select the "fast" definition of the {get,put}_be32() macros.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
---

I did consider adding an additional guard, like so:

    (defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))) || \

However, I decided that the extra paranoia was not needed ...


 block-sha1/sha1.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
index d893475..e102856 100644
--- a/block-sha1/sha1.c
+++ b/block-sha1/sha1.c
@@ -70,6 +70,7 @@
  */
 
 #if defined(__i386__) || defined(__x86_64__) || \
+    defined(_M_IX86) || defined(_M_X64) || \
     defined(__ppc__) || defined(__ppc64__) || \
     defined(__powerpc__) || defined(__powerpc64__) || \
     defined(__s390__) || defined(__s390x__)
-- 
1.7.1

Re: [PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[Jonathan Nieder]

Ramsay Jones wrote:

> diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
> index d893475..e102856 100644
> --- a/block-sha1/sha1.c
> +++ b/block-sha1/sha1.c
> @@ -70,6 +70,7 @@
>   */
>  
>  #if defined(__i386__) || defined(__x86_64__) || \
> +    defined(_M_IX86) || defined(_M_X64) || \
>      defined(__ppc__) || defined(__ppc64__) || \
>      defined(__powerpc__) || defined(__powerpc64__) || \
>      defined(__s390__) || defined(__s390x__)

Looks good to me, for what it’s worth.  You might want a similar
change on line 57:

 
-#if defined(__i386__) || defined(__x86_64__)
+#if defined(__i386__) || defined(__x86_64__) || \
+	defined(_M_IX86) || defined(_M_X64)
   #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))

Or alternatively, it might make sense to add something like the
following to compat/mingw.h or git-compat-util.h to fix this once.

 #if defined(_M_IX86) && !defined(__i386__)
 # define __i386__
 #endif
 #if defined(_M_X64) && !defined (__x86_64__)
 # define __x86_64__
 #endif

Thanks,
Jonathan

Re: [PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[Ramsay Jones]

Jonathan Nieder wrote:
> Ramsay Jones wrote:
> 
>> diff --git a/block-sha1/sha1.c b/block-sha1/sha1.c
>> index d893475..e102856 100644
>> --- a/block-sha1/sha1.c
>> +++ b/block-sha1/sha1.c
>> @@ -70,6 +70,7 @@
>>   */
>>  
>>  #if defined(__i386__) || defined(__x86_64__) || \
>> +    defined(_M_IX86) || defined(_M_X64) || \
>>      defined(__ppc__) || defined(__ppc64__) || \
>>      defined(__powerpc__) || defined(__powerpc64__) || \
>>      defined(__s390__) || defined(__s390x__)
> 
> Looks good to me, for what it’s worth.  You might want a similar
> change on line 57:
> 
>  
> -#if defined(__i386__) || defined(__x86_64__)
> +#if defined(__i386__) || defined(__x86_64__) || \
> +	defined(_M_IX86) || defined(_M_X64)
>    #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))

I looked at this, but decided not to make this change (while adding
an item to my TODO list to investigate further).

After reading the large comment before line 57, and with a vague
recollection of the mailing list discussion, I was left with the
impression that this was aimed specifically at a quirk of the gcc
code generator. In other words, maybe line 57 should read:

#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))

I don't know ... anyway I suspect that msvc has a different set of
code generation quirks! :-P

It should probably be investigated at some point, but I don't think
it's an urgent issue (and the msvc build will be no worse off ;-).

ATB,
Ramsay Jones

Re: [PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[Jonathan Nieder]

Ramsay Jones wrote:
> Jonathan Nieder wrote:

>> -#if defined(__i386__) || defined(__x86_64__)
>> +#if defined(__i386__) || defined(__x86_64__) || \
>> +	defined(_M_IX86) || defined(_M_X64)
>>    #define setW(x, val) (*(volatile unsigned int *)&W(x) = (val))
>
> I looked at this, but decided not to make this change (while adding
> an item to my TODO list to investigate further).

Mmm, my only complaint is that leaving out this change makes the
code appear to do something other than it does.  Maybe a comment
would help.

> After reading the large comment before line 57, and with a vague
> recollection of the mailing list discussion, I was left with the
> impression that this was aimed specifically at a quirk of the gcc
> code generator.

Sort of, but sort of not.  Using volatile here is saying “I really
want to do these stores in this order”.  And that is probably the
right thing to do for _any_ code generator on x86, unless it is very
smart.

> In other words, maybe line 57 should read:
>
> #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))

That would exclude icc etc so I’d prefer to avoid it without
empirical evidence.

> It should probably be investigated at some point, but I don't think
> it's an urgent issue (and the msvc build will be no worse off ;-).

Right, I agree with this. :)  So for what it’s worth:

  Acked-by: Jonathan Nieder <jrnieder@gmail.com>

I am referring to your original patch $gmane/149542 here.

Thanks.

Re: [PATCH 2/4] msvc: Select the "fast" definition of the {get,put}_be32() macros

[Ramsay Jones]

Jonathan Nieder wrote:
>> It should probably be investigated at some point, but I don't think
>> it's an urgent issue (and the msvc build will be no worse off ;-).
> 
> Right, I agree with this. :)  So for what it’s worth:
> 
>   Acked-by: Jonathan Nieder <jrnieder@gmail.com>

Thanks!

ATB,
Ramsay Jones