powerpc64le: blacklist broken GCC compilers (e.g GCC 7.5.0)

GCC 7.5.0 (PR94200) will refuse to compile if both -mabi=% and
-mlong-double-128 are passed on the command line.  Surprisingly,
it will work happily if the latter is not.  For the sake of
maintaining status quo, test for and blacklist such compilers.

Tested with a GCC 8.3.1 and GCC 7.5.0 compiler for ppc64le.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

3 files changed, 42 insertions, 12 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm-compat/Makefile b/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
index 0ac52a53bc..7b42746c34 100644
--- a/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
+++ b/sysdeps/ieee754/ldbl-128ibm-compat/Makefile
@@ -249,13 +249,6 @@ ldbl-extra-routines += err \
 CFLAGS-ieee128-qefgcvt.c += -mabi=ieeelongdouble -Wno-psabi -mno-gnu-attribute
 CFLAGS-ieee128-qefgcvt_r.c += -mabi=ieeelongdouble -Wno-psabi -mno-gnu-attribute
 
-# Remove -mlong-double-128 because it does not work correctly with
-# -mabi=ibmlongdoule in some GCC versions, e.g. GCC 7.
-$(foreach o,$(all-object-suffixes),$(objpfx)ieee128-qefgcvt$(o)): \
-  sysdep-CFLAGS := $(filter-out -mlong-double-128, $(sysdep-CFLAGS))
-$(foreach o,$(all-object-suffixes),$(objpfx)ieee128-qefgcvt_r$(o)): \
-  sysdep-CFLAGS := $(filter-out -mlong-double-128, $(sysdep-CFLAGS))
-
 tests-internal += tst-ibm128-warn tst-ieee128-warn
 tests-internal += tst-ibm128-error tst-ieee128-error
 tests-internal += tst-ibm128-efgcvt tst-ieee128-efgcvt
@@ -348,11 +341,6 @@ ldbl-ibm128-files := $(objpfx)test-%-ibm128^ \
 		     $(foreach r,$(ldbl-extra-routines),$(objpfx)$(r)-internal^)
 obj-suf-foreach = $(foreach suf,$(all-object-suffixes),$(subst ^,$(suf),$(1)))
 
-# Remove -mlong-double-128 because it does not work correctly with
-# -mabi=ibmlongdoule in some GCC versions, e.g. GCC 7.
-$(call obj-suf-foreach,$(ldbl-ibm128-files)): \
-  sysdep-CFLAGS := $(filter-out -mlong-double-128, $(sysdep-CFLAGS))
-
 # Explicitly add -mabi=ibm-long-double to required files.
 $(call obj-suf-foreach,$(ldbl-ibm128-files)): \
   sysdep-CFLAGS += -mabi=ibmlongdouble
diff --git a/sysdeps/powerpc/powerpc64/le/configure b/sysdeps/powerpc/powerpc64/le/configure
index bd7b8e77d0..98a4889945 100644
--- a/sysdeps/powerpc/powerpc64/le/configure
+++ b/sysdeps/powerpc/powerpc64/le/configure
@@ -90,6 +90,33 @@ 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 (PR83862)."
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if $CC compiles with -mabi=ieeelongdouble and -mlong-double-128" >&5
+$as_echo_n "checking if $CC compiles with -mabi=ieeelongdouble and -mlong-double-128... " >&6; }
+if ${libc_cv_compiler_powerpc64le_ldbl128_mabi+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  save_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mabi=ieeelongdouble -mlong-double-128"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+long double x;
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  libc_cv_compiler_powerpc64le_ldbl128_mabi=yes
+else
+  libc_cv_compiler_powerpc64le_ldbl128_mabi=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+CFLAGS="$save_CFLAGS"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_compiler_powerpc64le_ldbl128_mabi" >&5
+$as_echo "$libc_cv_compiler_powerpc64le_ldbl128_mabi" >&6; }
+if test "$libc_cv_compiler_powerpc64le_ldbl128_mabi" == "no"; then :
+  critic_missing="$critic_missing The compiler must support -mabi=ieeelongdouble and -mlongdouble simultaneously."
+fi
+
 for ac_prog in $OBJCOPY
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
diff --git a/sysdeps/powerpc/powerpc64/le/configure.ac b/sysdeps/powerpc/powerpc64/le/configure.ac
index 405933e710..769c06709e 100644
--- a/sysdeps/powerpc/powerpc64/le/configure.ac
+++ b/sysdeps/powerpc/powerpc64/le/configure.ac
@@ -51,6 +51,21 @@ 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 (PR83862)."])
 
+dnl Some old compiler versions give out error messages when combining
+dnl -mabi=% and -mlong-double-128.  i.e GCC 7.5.0 (PR94200)
+AC_CACHE_CHECK([if $CC compiles with -mabi=ieeelongdouble and -mlong-double-128],
+	       libc_cv_compiler_powerpc64le_ldbl128_mabi, [dnl
+save_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -mabi=ieeelongdouble -mlong-double-128"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
+long double x;
+]])],
+		  [libc_cv_compiler_powerpc64le_ldbl128_mabi=yes],
+		  [libc_cv_compiler_powerpc64le_ldbl128_mabi=no])
+CFLAGS="$save_CFLAGS"])
+AS_IF([test "$libc_cv_compiler_powerpc64le_ldbl128_mabi" == "no"],
+      [critic_missing="$critic_missing The compiler must support -mabi=ieeelongdouble and -mlongdouble simultaneously."])
+
 dnl objcopy (binutils) 2.26 or newer required to support the --update-section
 dnl feature for fixing up .gnu.attribute section with IEEE ldbl.
 AC_CHECK_PROG_VER(OBJCOPY, $OBJCOPY, --version,