| Message ID | 1498067125-30472-6-git-send-email-gftg@linux.vnet.ibm.com |
|---|---|
| State | New |
| Headers | show |
As far as I'm concerned this is for powerpc maintainers to review. Is the float128 connection that the float128 compiler support needs VSX to build / to build for the desired ABI?
On Wed, 21 Jun 2017 23:29:00 +0000 Joseph Myers <joseph@codesourcery.com> wrote: > As far as I'm concerned this is for powerpc maintainers to review. Is the > float128 connection that the float128 compiler support needs VSX to build > / to build for the desired ABI? Indeed, compiler support for float128 needs VSX. Once float128 support is enabled in glibc, builds for processors that don't provide VSX will fail, but will fail late. My intention with this patch is to fail as early as possible, and, since powerpc64le support starts with power8, I added this check to the powerpc64le-specific configure script.
On Thu, 2017-06-22 at 09:20 -0300, Gabriel F. T. Gomes wrote: > On Wed, 21 Jun 2017 23:29:00 +0000 > Joseph Myers <joseph@codesourcery.com> wrote: > > > As far as I'm concerned this is for powerpc maintainers to review. Is the > > float128 connection that the float128 compiler support needs VSX to build > > / to build for the desired ABI? > > Indeed, compiler support for float128 needs VSX. Once float128 support is > enabled in glibc, builds for processors that don't provide VSX will fail, > but will fail late. My intention with this patch is to fail as early as > possible, and, since powerpc64le support starts with power8, I added this > check to the powerpc64le-specific configure script. > In the PowerISA the IEEE Quad-Precision (IEEE float128) instructions are all defined as VSX Scalar. In the OpenPOWER ABI: 1) __float128 shall be recognized as a synonym for the _Float128 data type, and it is used interchangeably to refer to the same type. Implementations that do not offer support for _Float128 may provide this type with the __float128 type only. 2) For the purpose of determining a qualified floating-point argument, _Float128 shall be considered a vector data type. In addition, _Float128 is like a vector data type for determining if multiple aggregate members are like. 3) Binary extended precision numbers in IEEE BINARY 128 QUADRUPLE PRECISION format are passed (and returned) using a VMX register. Any resent GCC compiler (and certainly any GCC that supports _Float128) will happily spill any floating point temporary to and of the 64 VSX registers available. Also as __float128 is VSX scalar and many of the bit level operations are implemented via Vector logical or power8 direct move instructions the compiler requires -mvsx. This applies to our soft-float emulation of float128. So requiring VSX (capable compiler and hardware) to support float128 is reasonable.
On Thu, 22 Jun 2017, Steven Munroe wrote: > So requiring VSX (capable compiler and hardware) to support float128 is > reasonable. Is this your approval of this patch as powerpc maintainer, so Gabriel should now commit it?
On Thu, 2017-06-22 at 14:15 +0000, Joseph Myers wrote: > On Thu, 22 Jun 2017, Steven Munroe wrote: > > > So requiring VSX (capable compiler and hardware) to support float128 is > > reasonable. > > Is this your approval of this patch as powerpc maintainer, so Gabriel > should now commit it? > Yes I approve
diff --git a/sysdeps/powerpc/powerpc64le/configure b/sysdeps/powerpc/powerpc64le/configure index f5f1069..bf17d15 100644 --- a/sysdeps/powerpc/powerpc64le/configure +++ b/sysdeps/powerpc/powerpc64le/configure @@ -68,4 +68,34 @@ if test "$libc_cv_compiler_powerpc64le_compiler_ok" != "yes"; then : critic_missing="$critic_missing GCC >= 6.2 is required on powerpc64le." fi +OLD_CFLAGS="$CFLAGS" +CFLAGS="$CFLAGS $libc_cv_cc_submachine" +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if the target machine is at least POWER8" >&5 +$as_echo_n "checking if the target machine is at least POWER8... " >&6; } +if ${libc_cv_target_power8_ok+:} false; then : + $as_echo_n "(cached) " >&6 +else + +cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + +#ifndef _ARCH_PWR8 +#error invalid target architecture +#endif + +_ACEOF +if ac_fn_c_try_compile "$LINENO"; then : + libc_cv_target_power8_ok=yes +else + libc_cv_target_power8_ok=no +fi +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_target_power8_ok" >&5 +$as_echo "$libc_cv_target_power8_ok" >&6; } +if test "$libc_cv_target_power8_ok" != "yes"; then : + critic_missing="$critic_missing POWER8 or newer is required on powerpc64le." +fi +CFLAGS="$OLD_CFLAGS" + test -n "$critic_missing" && as_fn_error $? "*** $critic_missing" "$LINENO" 5 diff --git a/sysdeps/powerpc/powerpc64le/configure.ac b/sysdeps/powerpc/powerpc64le/configure.ac index 9d8c54c..53d8e12 100644 --- a/sysdeps/powerpc/powerpc64le/configure.ac +++ b/sysdeps/powerpc/powerpc64le/configure.ac @@ -14,4 +14,20 @@ AC_PREPROC_IFELSE([AC_LANG_SOURCE([[ AS_IF([test "$libc_cv_compiler_powerpc64le_compiler_ok" != "yes"], [critic_missing="$critic_missing GCC >= 6.2 is required on powerpc64le."]) +dnl Require at least POWER8 on powerpc64le +OLD_CFLAGS="$CFLAGS" +CFLAGS="$CFLAGS $libc_cv_cc_submachine" +AC_CACHE_CHECK([if the target machine is at least POWER8], + libc_cv_target_power8_ok, [ +AC_COMPILE_IFELSE([AC_LANG_SOURCE([[ +#ifndef _ARCH_PWR8 +#error invalid target architecture +#endif +]])], + [libc_cv_target_power8_ok=yes], + [libc_cv_target_power8_ok=no])]) +AS_IF([test "$libc_cv_target_power8_ok" != "yes"], + [critic_missing="$critic_missing POWER8 or newer is required on powerpc64le."]) +CFLAGS="$OLD_CFLAGS" + test -n "$critic_missing" && AC_MSG_ERROR([*** $critic_missing])