2014-05-07 1:32 GMT+02:00 Eliot Miranda <eliot.miranda@gmail.com>:
Hi Nicolai,On Tue, May 6, 2014 at 4:14 AM, Nicolai Hess <nicolaihess@web.de> wrote:
2014-05-05 20:37 GMT+02:00 Eliot Miranda <eliot.miranda@gmail.com>:
Hi Nicolai,On Mon, May 5, 2014 at 12:06 AM, Nicolai Hess <nicolaihess@web.de> wrote:
2014-04-03 17:51 GMT+02:00 karl ramberg <karlramberg@gmail.com>:
I can confirm this bug on windows Cog.Cheers,KarlOn Thu, Apr 3, 2014 at 10:11 AM, Nicolai Hess <nicolaihess@web.de> wrote:
This one is active and causes this error.bitdepths with big endian to convert to lsbpharo 30793 image with latest vm from http://files.pharo.org/vm/pharo/win/There is still something wrong with byte/word swap in windows ioShowDisplay codesqueak 4.5 image with cogvm from http://files.pharo.org/vm/cogmt/win/
attached are two screenshots
showing this bug after setting the Display depth to 16sqwin32window.c has three variants for doing the byte_swap/word_swap on
(Display newDepth:16)
# if __GNUC__ >= 3
# define BYTE_SWAP(w) __asm__("bswap %0" : "=r" (w) : "r" (w))
# define WORD_SWAP(w) __asm__("roll $16, %0" : "=r" (w) : "r" (w))
This one would work
# else
# define BYTE_SWAP(w) __asm__("bswap %%eax" : "=eax" (w) : "eax" (w))
# define WORD_SWAP(w) __asm__("roll $16, %%eax" : "=eax" (w) : "eax" (w))
This one, of course, works too
# else
# define BYTE_SWAP(w) w = (w << 24) | ((w & 0xFF00) << 8) | ((w >> 8) & 0xFF00) | (w >> 24)
# define WORD_SWAP(w) w = (( (unsigned)(w) << 16) | ((unsigned) (w) >> 16))
This one is not there but would work (at least with gcc > 4.5
# define BYTE_SWAP_MY(w) __asm__("bswap %0" : "+r" (w))
# define WORD_SWAP_MY(w) __asm__("roll $16, %0" : "+r" (w))
But actually I don't know assembler and/or the gcc inline code syntax, so
I don't know what is wrong with the first version :)Nicolaibtw, you can not test this bug with the current squeak 4.5 all in on image,
as it uses a rather old vm.
Third screenshot:
using the latest stable pharo-vm, it looks much more wrong, as there
was another(?) bug that is fixed already(?) - i don't know :)Someone else can reproduce this?(eliot?, nicolas? )It is easily fixable, I think. But I am not good at inline assembler.
I'll open a mantis and fogbugz report.Yes, I can reproduce it. But I've not had time to check with a pre 3.x and a post 3.x compiler to check what the right syntax is. I'm busy with other stuff right now. Hopefully I'll get to this in a coupel of weeks. Anyone else out there who can provide the right syntax for2.953.4.x4.xI'd be very grateful and simply integrate the fix.--best,EliotOk, thank you eliot.I think I know now way the first version does not work:
__asm__("bswap %0" : "=r" (w) : "r" (w))
The compiler might generate code like this, just:bswap %ebxwithout initialisation of that register (although we declare "r"(w) as input).
It behaves like that, because an output register is supposed to be overwritten :)and the bswap command only uses the %0 (the first register in the output : input register list).
The proper way for defining an register as output-input (or read-write register) would be__asm__("bswap %0" : "+r" (w) )Some asm-inline tutorials mention, this(the "+" constraint modifier) would not work on all compilers and
prefer another older syntax:
__asm__("bswap %0" : "=r" (w) : "0" (w))
(use the 0th output register for input too)Yes, I think you're exactly right (IIRC).But even the gcc2.95 doc (http://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_16.html#IDX955)
lists "+" as allowed constraint modifier, so, I think it should work.Ah, so the hope is that the older syntax will work on all versions? That would be sweet.No, actually I hope, that the recommended syntax works with all versions.It is difficult to setup a complete build environment with the older gcc-versions.
(Do we really need compatiblity with gcc 2.95?)Anyway, I installed the core gcc-binaries for
2.95
3.3.1
4.7.2and just took the assembler output.They don't generate the "same" code, but all generating working code.
-> move argument from stack to X-> do operation on X-> move argument backSo,
# define BYTE_SWAP(w) __asm__("bswap %0" : "+r" (w))
# define WORD_SWAP(w) __asm__("roll $16, %0" : "+r" (w))works.
I'll test this with different gcc versions and compare the compiler output
(after I found out how to install multiple mingw versions :) )nicolai--
best,Eliot