[glibc/azanella/clang] Use -ffloat-store iff compiler supports it

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=58c049fccb3b6a40f88a7c14600677ca8da1fa5e

commit 58c049fccb3b6a40f88a7c14600677ca8da1fa5e
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Thu Mar 24 13:12:43 2022 -0300

    Use -ffloat-store iff compiler supports it

Diff:
---
 configure     | 24 ++++++++++++++++++++++++
 configure.ac  | 10 ++++++++++
 math/Makefile |  4 ++--
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index 004108d180..0f3c8818d3 100755
--- a/configure
+++ b/configure
@@ -7466,6 +7466,30 @@ printf "%s\n" "$libc_cv_cc_rounding_math" >&6; }
 config_vars="$config_vars
 config-cflags-frounding-math = $libc_cv_cc_rounding_math"
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for compiler option that -ffloat-store" >&5
+printf %s "checking for compiler option that -ffloat-store... " >&6; }
+if test ${libc_cv_cc_float_store+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+  if { ac_try='${CC-cc} -Werror -ffloat-store -xc /dev/null -S -o /dev/null'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  printf "%s\n" "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then :
+  libc_cv_cc_float_store=-ffloat-store
+else $as_nop
+  libc_cv_cc_float_store=
+fi
+
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_cc_float_store" >&5
+printf "%s\n" "$libc_cv_cc_float_store" >&6; }
+config_vars="$config_vars
+config-cflags-float-store = $libc_cv_cc_float_store"
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking if $CC accepts -fno-tree-loop-distribute-patterns with \
 __attribute__ ((__optimize__))" >&5
 printf %s "checking if $CC accepts -fno-tree-loop-distribute-patterns with \
diff --git a/configure.ac b/configure.ac
index ecb4e7086e..7a9df2818a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1535,6 +1535,16 @@ LIBC_TRY_CC_OPTION([-Werror -frounding-math],
 LIBC_CONFIG_VAR([config-cflags-frounding-math],
 	       	[$libc_cv_cc_rounding_math])
 
+dnl Determine if compiler supports -ffloat-store
+AC_CACHE_CHECK([for compiler option that -ffloat-store],
+	       libc_cv_cc_float_store, [dnl
+LIBC_TRY_CC_OPTION([-Werror -ffloat-store],
+		   [libc_cv_cc_float_store=-ffloat-store],
+		   [libc_cv_cc_float_store=])
+])
+LIBC_CONFIG_VAR([config-cflags-float-store],
+		[$libc_cv_cc_float_store])
+
 AC_CACHE_CHECK(if $CC accepts -fno-tree-loop-distribute-patterns with \
 __attribute__ ((__optimize__)), libc_cv_cc_loop_to_function, [dnl
 cat > conftest.c <<EOF
diff --git a/math/Makefile b/math/Makefile
index 3e9701c0d1..85a9cb3026 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -407,7 +407,7 @@ $(objpfx)test-tgmath3-macro-list.out: gen-tgmath-tests.py
 
 libm-test-fast-math-cflags = -fno-builtin -D__FAST_MATH__ -DTEST_FAST_MATH
 libm-test-vec-cflags = $(libm-test-fast-math-cflags) -fno-inline \
-		       -ffloat-store -D_OPENMP=201307 -Wno-unknown-pragmas
+		       $(libc_cv_cc_float_store) -D_OPENMP=201307 -Wno-unknown-pragmas
 
 CFLAGS-test-double-vlen4-wrappers.c += $(double-vlen4-arch-ext-cflags)
 
@@ -423,7 +423,7 @@ CFLAGS-test-float-vlen16-wrappers.c += $(float-vlen16-arch-ext-cflags)
 # raise spurious exceptions for sNaNs, but also do not test for
 # exceptions.  Thus both versions of the classification macros are
 # validated.
-libm-test-no-inline-cflags = -fno-inline -ffloat-store -fno-builtin \
+libm-test-no-inline-cflags = -fno-inline $(libc_cv_cc_float_store) -fno-builtin \
 			     $(config-cflags-signaling-nans)
 CFLAGS-test-tgmath.c += -fno-builtin
 # The following testcase uses very long lines (>3 million), so it may take a