S390: Do not set FE_INEXACT with feraiseexcept (FE_OWERFLOW|FE_UNDERFLOW).

On s390 feraiseexcept (FE_OVERFLOW|FE_UNDERFLOW) sets FE_INEXACT, too.
This patch uses z196 zarch load rounded instruction which can suppress
FE_INEXACT exception if gcc has z196 support in used configuration.
Otherwise FE_INEXACT flag is set as before. The gcc support is tested
in a new configure-check.

A comment in fsetexcptflg.c is corrected as new exceptions are not
executed with the next floating-point instruction if fpc is set with
_FPU_SETCW macro. It seems the comment was copied e.g. from
sysdeps/x86_64/fpu/fsetexcptflg.c file.

ChangeLog:

	* config.h.in (HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT):
	New undefine.
	* sysdeps/s390/configure.ac: Add test for z196 zarch support.
	* sysdeps/s390/configure: Regenerated.
	* sysdeps/s390/fpu/fraiseexcpt.c (__feraiseexcept): Use ledbra
	instruction for raising over-/underflow if z196 zarch is supported
	by default.
	* sysdeps/s390/fpu/fsetexcptflg.c (fesetexceptflag):
	Correct comment.

1 files changed, 36 insertions, 0 deletions

diff --git a/sysdeps/s390/configure b/sysdeps/s390/configure
index c9fb69cd6c..347ac28528 100644
--- a/sysdeps/s390/configure
+++ b/sysdeps/s390/configure
@@ -177,5 +177,41 @@ then
 
 fi
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for S390 z196 zarch instruction support as default" >&5
+$as_echo_n "checking for S390 z196 zarch instruction support as default... " >&6; }
+if ${libc_cv_asm_s390_min_z196_zarch+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<\EOF
+float testinsn (double e)
+{
+    float d;
+    __asm__ ("ledbra %0,5,%1,4" : "=f" (d) : "f" (e) );
+    return d;
+}
+EOF
+if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS --shared conftest.c
+			-o conftest.o &> /dev/null'
+  { { eval echo "\"\$as_me\":${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_asm_s390_min_z196_zarch=yes
+else
+  libc_cv_asm_s390_min_z196_zarch=no
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_asm_s390_min_z196_zarch" >&5
+$as_echo "$libc_cv_asm_s390_min_z196_zarch" >&6; }
+
+if test "$libc_cv_asm_s390_min_z196_zarch" = yes ;
+then
+  $as_echo "#define HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT 1" >>confdefs.h
+
+fi
+
 test -n "$critic_missing" && as_fn_error $? "
 *** $critic_missing" "$LINENO" 5