[glibc/azanella/clang] x86: Use -mfpmath=387 iff compiler supports it

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=3209c25fd301f5e74a3c2687af628e823a83c221

commit 3209c25fd301f5e74a3c2687af628e823a83c221
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Mar 24 15:02:05 2022 -0300

    x86: Use -mfpmath=387 iff compiler supports it

Diff:
---
 sysdeps/x86/configure    | 22 ++++++++++++++++++++++
 sysdeps/x86/configure.ac | 10 ++++++++++
 sysdeps/x86/fpu/Makefile |  5 ++++-
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/sysdeps/x86/configure b/sysdeps/x86/configure
index 46d436fddf..26296b0aea 100644
--- a/sysdeps/x86/configure
+++ b/sysdeps/x86/configure
@@ -190,6 +190,28 @@ fi
 config_vars="$config_vars
 enable-x86-isa-level = $libc_cv_include_x86_isa_level"
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler supports -mpfmath=387" >&5
+$as_echo_n "checking if compiler supports -mpfmath=387... " >&6; }
+if ${libc_cv_cc_mfpmath_387+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if { ac_try='${CC-cc} -Werror -mfpmath=387 -xc /dev/null -S -o /dev/null'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }; then :
+  libc_cv_cc_mfpmath_387="-mfpmath=387"
+else
+  libc_cv_cc_mfpmath_387=
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_mfpmath_387" >&5
+$as_echo "$libc_cv_cc_mfpmath_387" >&6; }
+config_vars="$config_vars
+config-cflags-mfpath-387 = $libc_cv_cc_mfpmath_387"
+
 $as_echo "#define PI_STATIC_AND_HIDDEN 1" >>confdefs.h
 
 
diff --git a/sysdeps/x86/configure.ac b/sysdeps/x86/configure.ac
index 918b636891..8c2970864a 100644
--- a/sysdeps/x86/configure.ac
+++ b/sysdeps/x86/configure.ac
@@ -128,6 +128,16 @@ if test $libc_cv_include_x86_isa_level = yes; then
 fi
 LIBC_CONFIG_VAR([enable-x86-isa-level], [$libc_cv_include_x86_isa_level])
 
+dnl Determine if compiler supports -mfpmath=387
+AC_CACHE_CHECK([if compiler supports -mpfmath=387],
+	       libc_cv_cc_mfpmath_387, [dnl
+LIBC_TRY_CC_OPTION([-Werror -mfpmath=387],
+		   [libc_cv_cc_mfpmath_387="-mfpmath=387"],
+		   [libc_cv_cc_mfpmath_387=])
+])
+LIBC_CONFIG_VAR([config-cflags-mfpath-387],
+		[$libc_cv_cc_mfpmath_387])
+
 dnl It is always possible to access static and hidden symbols in an
 dnl position independent way.
 AC_DEFINE(PI_STATIC_AND_HIDDEN)
diff --git a/sysdeps/x86/fpu/Makefile b/sysdeps/x86/fpu/Makefile
index 68bd42cdd3..2d584dbfeb 100644
--- a/sysdeps/x86/fpu/Makefile
+++ b/sysdeps/x86/fpu/Makefile
@@ -4,7 +4,10 @@ CPPFLAGS += -I../soft-fp
 
 libm-support += powl_helper
 tests += test-fenv-sse test-fenv-clear-sse test-fenv-x87 test-fenv-sse-2 \
-	 test-flt-eval-method-387 test-flt-eval-method-sse
+	 test-flt-eval-method-sse
+ifneq ($(config-cflags-mfpath-387),)
+tests += test-flt-eval-method-387
+endif
 CFLAGS-test-fenv-sse.c += -msse2 -mfpmath=sse
 CFLAGS-test-fenv-clear-sse.c += -msse2 -mfpmath=sse
 CFLAGS-test-fenv-sse-2.c += -msse2 -mfpmath=sse