package/libmpeg2/0003-fix-arm-detection.patch

   1 Improve the ARM detection to work on Thumb-only architecture
   2
   3 The ARM-specific assembly code doesn't build on Thumb-only
   4 architectures such as ARMv7-M, but the configure script assumes that
   5 if the host tuple is arm*, then it can build and use the ARM optimized
   6 code.
   7
   8 This patch improves the configure.ac detection logic, by building one
   9 of the instruction of the optimized assembly code, and using this to
  10 decide whether or not the optimizations should be enabled.
  11
  12 Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
  13
  14 Index: b/configure.ac
  15 ===================================================================
  16 --- a/configure.ac
  17 +++ b/configure.ac
  18 @@ -101,8 +101,10 @@
  19      alpha*)
  20         AC_DEFINE([ARCH_ALPHA],,[alpha architecture]);;
  21      arm*)
  22 -       arm_conditional=:
  23 -       AC_DEFINE([ARCH_ARM],,[ARM architecture]);;
  24 +       AC_TRY_LINK([], [asm(".syntax divided\nstmfd sp!,{r4-r11,lr}")],
  25 +            [AC_DEFINE([ARCH_ARM],,[ARM architecture])
  26 +             use_arm_optimization=yes],
  27 +            [use_arm_optimization=no])
  28      esac
  29  elif test x"$CC" = x"tendracc"; then
  30      dnl TenDRA portability checking compiler
  31 @@ -122,7 +124,7 @@
  32      esac
  33  fi
  34
  35 -AM_CONDITIONAL(ARCH_ARM, ${arm_conditional})
  36 +AM_CONDITIONAL(ARCH_ARM, test "${use_arm_optimization}" = "yes")
  37
  38  dnl Checks for libtool - this must be done after we set cflags
  39  AC_LIBTOOL_WIN32_DLL