On 21 January 2015 at 11:42, Edward Nevill <edward.nev...@linaro.org> wrote:
> Hi, > > Hadoop currently does not build on ARM AARCH64. I have raised a JIRA issue > with a patch. > > https://issues.apache.org/jira/browse/HADOOP-11484 > > I have submitted the patch and it builds OK and passes all the core tests. > Hi Colin, Thanks for pushing this patch. Steve Loughran raised the issue in the card that although this patch fixes the ARM issue it does nothing for other archs. I would be happy to prepare a patch which makes it downgrade to C code on other CPU families if this would be useful. The general format would be #idef __aarch64__ __asm__("ARM Asm") #elif defined(??X86??) __asm__("X86 Asm") #else C Implementation #endif My question is what to put for the defined(??X86??) According to the following page http://nadeausoftware.com/articles/2012/02/c_c_tip_how_detect_processor_type_using_compiler_predefined_macros the only way to fully detect all x86 variants is to write #if defined(__x86_64__) || defined(_M_X64) || defined(__i386) || defined(_M_IX86) will detect all variants of 32 and 64 bit x86 across gcc and windows. Interestingly the bswap64 inline function in primitives.h has the following #ifdef __X64 __asm__("rev ...."); #else C implementation #endif However if I compile Hadoop on my 64 bit Red Hat Enterprise Linux system it actually compiles the C implementation (I have verified this by putting a #error at the start of the C implementation. This is because the correct macro to detect 64 bit x86 on gcc is __x86_64__ I had also thought that the macro for windows was _M_X64 not __X64 but maybe __X64 works just as well on windows? Perhaps someone with access to windows development platform could do some tests and tell us what macros actually work. Another question is whether we actually care about 32 bit platforms, or can they just all downgrade to C code. Does anyone actually build Hadoop on a 32 bit platform? Another thing to be aware of is that there are endian dependncies in primitives.h, for example in fmemcmp() just a bit further down is the line return (int64_t)bswap(*(uint32_t*)src) - (int64_t)bswap(*(uint32_t*)dest); This is little endian dependant so will work on the likes of X86 and ARM but will fail on Sparc. Note, I haven't trawled looking for endian dependancies but this was one I just spotted while looking at the aarch64 non compilation issue. All the best, Ed.
