• Thomas Petazzoni's avatar
    build: fix architecture detection · ff77a85c
    Thomas Petazzoni authored
    
    
    The current architecture detection, based on the "host_cpu" part of the
    tuple does not work properly for a number of reason:
    
     - The code assumes that if host_cpu starts with "arm" then ARM
       instructions are available, which is incorrect. Indeed, Cortex-M
       platforms can run Linux, they are ARM platforms (so host_cpu = arm),
       but they don't support ARM instructions: they support only the
       Thumb-2 instruction set.
    
     - The armv7 case is also not very useful, as it is not standard at all
       to pass armv7 as host_cpu even if the host system is actually ARMv7
       based.
    
     - For the same reason, the armv8 case is not very useful: ARMv8 is
       AArch64, and there is already a separate case to handle this
       architecture.
    
    So, this commit moves away from a host_cpu based logic, and instead
    tests using AC_CHECK_DECLS() the built-in definitions of the compiler:
    
     - If we have __ARM_ARCH_ISA_ARM defined, then it's an ARM processor
       that supports the ARM instruction set (this allows to exclude Thumb-2
       only processors).
    
     - If we have __ARM_ARCH_7A__, then we have an ARMv7-A processor, and
       we can enable the corresponding optimizations
    
     - Same for __aarch64__, __i386__ and __x86_64__.
    
    In addition, we remove the AC_MSG_ERROR() that makes the build fail for
    all architectures but the ones that are explicitly supported. Indeed,
    webrtc-audio-processing builds just fine for other architectures (tested
    on MIPS), it's just that none of the architecture-specific optimizations
    will be used.
    Signed-off-by: default avatarThomas Petazzoni <thomas.petazzoni@free-electrons.com>
    ff77a85c
configure.ac 4.36 KB