@@ -467,6 +467,12 @@ build the GNU C Library:
better code. As of release time, GCC 9.2.1 is the newest compiler
verified to work to build the GNU C Library.
+ For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
+ support for '-mno-gnu-attribute' is required. As of release time,
+ this means GCC 7.4 (excepting 7.5) or newer. The compiler option
+ is required for building the GNU C Library with support for IEEE
+ long double.
+
For multi-arch support it is recommended to use a GCC which has
been built with support for GNU indirect functions. This ensures
that correct debugging information is generated for functions
@@ -20,7 +20,8 @@ Deprecated and removed features, and other changes affecting compatibility:
Changes to build and runtime requirements:
- [Add changes to build and runtime requirements here]
+* powerpc64le requires GCC 7.4 or newer. This is required for supporting
+ long double redirects.
Security related changes:
@@ -507,6 +507,11 @@ the newest version of the compiler that is known to work for building
release time, GCC 9.2.1 is the newest compiler verified to work to build
@theglibc{}.
+For PowerPC 64-bits little-endian (powerpc64le), a GCC version with
+support for @option{-mno-gnu-attribute} is required. As of release time,
+this means GCC 7.4 (excepting 7.5) or newer. The compiler option is required
+for building the GNU C Library with support for IEEE long double.
+
For multi-arch support it is recommended to use a GCC which has been built with
support for GNU indirect functions. This ensures that correct debugging
information is generated for functions selected by IFUNC resolvers. This
@@ -32,4 +32,63 @@ if test "$libc_cv_target_power8_ok" != "yes"; then :
fi
CFLAGS="$OLD_CFLAGS"
+OLD_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mno-gnu-attribute"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if the compiler supports -mno-gnu-attribute" >&5
+$as_echo_n "checking if the compiler supports -mno-gnu-attribute... " >&6; }
+if ${libc_cv_no_gnu_attr_ok+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+ libc_cv_no_gnu_attr_ok=yes
+else
+ libc_cv_no_gnu_attr_ok=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_no_gnu_attr_ok" >&5
+$as_echo "$libc_cv_no_gnu_attr_ok" >&6; }
+if test "$libc_cv_no_gnu_attr_ok" != "yes"; then :
+ critic_missing="$critic_missing A compiler with -mno-gnu-attribute is required on powerpc64le."
+fi
+CFLAGS="$OLD_CFLAGS"
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if $CC compiles signbit with 128-bit floating point type" >&5
+$as_echo_n "checking if $CC compiles signbit with 128-bit floating point type... " >&6; }
+if ${libc_cv_compiler_powerpc64le_ice+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ save_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mabi=ieeelongdouble -Wno-psabi"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+int sbr (long double a) { return __builtin_signbit (a); }
+int sbm (long double *a) { return __builtin_signbit (*a); }
+int sbo (long double *a) { return __builtin_signbit (a[4]); }
+int sbi (long double *a, unsigned long n) { return __builtin_signbit (a[n]); }
+void sbs (int *p, long double a) { *p = __builtin_signbit (a); }
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+ libc_cv_compiler_powerpc64le_ice=yes
+else
+ libc_cv_compiler_powerpc64le_ice=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+CFLAGS="$save_CFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_compiler_powerpc64le_ice" >&5
+$as_echo "$libc_cv_compiler_powerpc64le_ice" >&6; }
+if test "$libc_cv_compiler_powerpc64le_ice" != "yes"; then :
+ critic_missing="$critic_missing __builtin_signbit is broken. GCC 7.4 or newer is required to resolve (BZ 83862)."
+fi
+
+
test -n "$critic_missing" && as_fn_error $? "*** $critic_missing" "$LINENO" 5
@@ -17,4 +17,39 @@ AS_IF([test "$libc_cv_target_power8_ok" != "yes"],
[critic_missing="$critic_missing POWER8 or newer is required on powerpc64le."])
CFLAGS="$OLD_CFLAGS"
+dnl Require support for -mno-gnu-attribute
+OLD_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mno-gnu-attribute"
+AC_CACHE_CHECK([if the compiler supports -mno-gnu-attribute],
+ libc_cv_no_gnu_attr_ok, [
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+]])],
+ [libc_cv_no_gnu_attr_ok=yes],
+ [libc_cv_no_gnu_attr_ok=no])])
+AS_IF([test "$libc_cv_no_gnu_attr_ok" != "yes"],
+ [critic_missing="$critic_missing A compiler with -mno-gnu-attribute is required on powerpc64le."])
+CFLAGS="$OLD_CFLAGS"
+
+dnl Some old compiler versions give error for the function signbit() for
+dnl 128-bit floating point types. This is fixed by BZ 83862 and backported
+dnl to gcc6 and gcc7. This test is to check if we are using the compiler
+dnl that has this bug. (available in GCC 8.0).
+AC_CACHE_CHECK([if $CC compiles signbit with 128-bit floating point type],
+ libc_cv_compiler_powerpc64le_ice, [dnl
+save_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mabi=ieeelongdouble -Wno-psabi"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+int sbr (long double a) { return __builtin_signbit (a); }
+int sbm (long double *a) { return __builtin_signbit (*a); }
+int sbo (long double *a) { return __builtin_signbit (a[4]); }
+int sbi (long double *a, unsigned long n) { return __builtin_signbit (a[n]); }
+void sbs (int *p, long double a) { *p = __builtin_signbit (a); }
+]])],
+ [libc_cv_compiler_powerpc64le_ice=yes],
+ [libc_cv_compiler_powerpc64le_ice=no])
+CFLAGS="$save_CFLAGS"])
+AS_IF([test "$libc_cv_compiler_powerpc64le_ice" != "yes"],
+ [critic_missing="$critic_missing __builtin_signbit is broken. GCC 7.4 or newer is required to resolve (BZ 83862)."])
+
+
test -n "$critic_missing" && AC_MSG_ERROR([*** $critic_missing])
Add compiler feature tests to ensure we can build ieee128 long double. These test for -mabi=ieeelongdouble, -mno-gnu-attribute, and -Wno-psabi. Likewise, verify some compiler bugs have been addressed. These aren't helpful for building glibc, but may cause test failures when testing the new long double. See notes below from Raji. On powerpc64le, some older compiler versions give error for the function signbit() for 128-bit floating point types. This is fixed by PR83862 in gcc 8.0 and backported to gcc6 and gcc7. This patch adds a test to check compiler version to avoid compiler errors during make check. Likewise, test for -mno-gnu-attribute support which was On powerpc64le, a few files are built on IEEE long double mode (-mabi=ieeelongdouble), whereas most are built on IBM long double mode (-mabi=ibmlongdouble, the default for -mlong-double-128). Since binutils 2.31, linking object files with different long double modes causes errors similar to: ld: libc_pic.a(s_isinfl.os) uses IBM long double, libc_pic.a(ieee128-qefgcvt.os) uses IEEE long double. collect2: error: ld returned 1 exit status make[2]: *** [../Makerules:649: libc_pic.os] Error 1 The warnings are fair and correct, but in order for glibc to have support for both long double modes on powerpc64le, they have to be ignored. This can be accomplished with the use of -mno-gnu-attribute option when building the few files that require IEEE long double mode. However, -mno-gnu-attribute is not available in GCC 6, the minimum version required to build glibc, so this patch adds a test for this feature in powerpc64le builds, and fails early if it's not available. Co-Authored-By: Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com> Co-Authored-By: Gabriel F. T. Gomes <gabrielftg@linux.ibm.com> --- INSTALL | 6 +++ NEWS | 3 +- manual/install.texi | 5 ++ sysdeps/powerpc/powerpc64/le/configure | 59 +++++++++++++++++++++++ sysdeps/powerpc/powerpc64/le/configure.ac | 35 ++++++++++++++ 5 files changed, 107 insertions(+), 1 deletion(-)