impossible constraint in 'asm'

[nomeata]

Hi,

criterion-1.1.0.0 fails to build on arm* and powerpc:

[13 of 13] Compiling Criterion        ( Criterion.hs, dist-ghc/build/Criterion.p_o )
cbits/cycles.c: In function 'criterion_rdtsc':

cbits/cycles.c:6:3:
     error: impossible constraint in 'asm'
       __asm__ __volatile__ ("rdtsc" : "=a"(lo), "=d"(hi));
       ^
make: *** [build-ghc-stamp] Error 1
/usr/share/cdbs/1/class/hlibrary.mk:133: recipe for target 'build-ghc-stamp' failed

https://buildd.debian.org/status/fetch.php?pkg=haskell-criterion&arch=armel&ver=1.1.0.0-2&stamp=1430704376
https://buildd.debian.org/status/fetch.php?pkg=haskell-criterion&arch=armhf&ver=1.1.0.0-2&stamp=1430808023
https://buildd.debian.org/status/fetch.php?pkg=haskell-criterion&arch=powerpc&ver=1.1.0.0-2&stamp=1431220028

Do you have an idea what’s wrong and how to fix it?

[bos]

That's some inline assembly code that only works on i386 and x86_64. You'll want to write some sort of equivalent code for other platforms, ideally using a cycle-accurate counter like the x86 TSC. Something like clock_gettime will work more portably in extremis, but it'll be dramatically less accurate.

[nomeata]

So you are saying that criterion simply does not support anything but i386 and x86_64 for now? Maybe you can conditionally set buildable: False in the cabal file to communicate that better.

[bos]

I've never encountered a user on another platform. I'm happy to accept suitable patches, but I'm not going to write them myself as obviously I can't test them :-)

[egrimley]

Are you sure that clock_gettime(CLOCK_MONOTONIC, &t) is dramatically less accurate? My understanding is that clock_gettime may use the TSC, where it is available, without doing a system call (when the program is dynamically linked). Also, how are you tackling the problems of TSC on a multi-core system, as described for example in https://en.wikipedia.org/wiki/Time_Stamp_Counter ?

[bos]

Fixed by 0673606.