Fortran: Allow IEEE_CLASS to identify signaling NaNs

We use the issignaling macro, present in some libc's (notably glibc),
when it is available. Compile all IEEE-related files in the library
(both C and Fortran sources) with -fsignaling-nans to ensure maximum
compatibility.

libgfortran/ChangeLog:

	PR fortran/82207
	* Makefile.am: Pass -fsignaling-nans for IEEE files.
	* Makefile.in: Regenerate.
	* ieee/ieee_helper.c: Use issignaling macro to recognized
	signaling NaNs.

gcc/testsuite/ChangeLog:

	PR fortran/82207
	* gfortran.dg/ieee/signaling_1.f90: New test.
	* gfortran.dg/ieee/signaling_1_c.c: New file.

3 files changed, 25 insertions, 4 deletions

diff --git a/libgfortran/Makefile.am b/libgfortran/Makefile.am
index 008f2e7..b7ef912 100644
--- a/libgfortran/Makefile.am
+++ b/libgfortran/Makefile.am
@@ -185,6 +185,8 @@ endif
 
 if IEEE_SUPPORT
 
+gfor_ieee_helper_src=ieee/ieee_helper.c
+
 gfor_helper_src+=ieee/ieee_helper.c
 
 gfor_ieee_src= \
@@ -991,9 +993,13 @@ selected_real_kind.lo selected_int_kind.lo: AM_FCFLAGS += -fallow-leading-unders
 
 if IEEE_SUPPORT
 # Add flags for IEEE modules
-$(patsubst %.F90,%.lo,$(notdir $(gfor_ieee_src))): AM_FCFLAGS += -Wno-unused-dummy-argument -Wno-c-binding-type -ffree-line-length-0 -fallow-leading-underscore
+$(patsubst %.F90,%.lo,$(notdir $(gfor_ieee_src))): AM_FCFLAGS += -Wno-unused-dummy-argument -Wno-c-binding-type -ffree-line-length-0 -fallow-leading-underscore -fsignaling-nans
+
+# Add flags for IEEE helper code
+$(patsubst %.c,%.lo,$(notdir $(gfor_ieee_helper_src))): AM_CFLAGS += -fsignaling-nans
 endif
 
+
 # Dependencies between IEEE_ARITHMETIC and IEEE_EXCEPTIONS
 ieee_arithmetic.lo: ieee/ieee_arithmetic.F90 ieee_exceptions.lo
 	$(LTPPFCCOMPILE) -c -o $@ $<
diff --git a/libgfortran/Makefile.in b/libgfortran/Makefile.in
index 5dac04e..3684b2a 100644
--- a/libgfortran/Makefile.in
+++ b/libgfortran/Makefile.in
@@ -779,6 +779,7 @@ gfor_helper_src = intrinsics/associated.c intrinsics/abort.c \
 	intrinsics/selected_real_kind.f90 intrinsics/trigd.c \
 	intrinsics/unpack_generic.c runtime/in_pack_generic.c \
 	runtime/in_unpack_generic.c $(am__append_3) $(am__append_4)
+@IEEE_SUPPORT_TRUE@gfor_ieee_helper_src = ieee/ieee_helper.c
 @IEEE_SUPPORT_FALSE@gfor_ieee_src = 
 @IEEE_SUPPORT_TRUE@gfor_ieee_src = \
 @IEEE_SUPPORT_TRUE@ieee/ieee_arithmetic.F90 \
@@ -6999,7 +7000,10 @@ $(patsubst %.F90,%.lo,$(patsubst %.f90,%.lo,$(notdir $(gfor_specific_src)))): AM
 selected_real_kind.lo selected_int_kind.lo: AM_FCFLAGS += -fallow-leading-underscore
 
 # Add flags for IEEE modules
-@IEEE_SUPPORT_TRUE@$(patsubst %.F90,%.lo,$(notdir $(gfor_ieee_src))): AM_FCFLAGS += -Wno-unused-dummy-argument -Wno-c-binding-type -ffree-line-length-0 -fallow-leading-underscore
+@IEEE_SUPPORT_TRUE@$(patsubst %.F90,%.lo,$(notdir $(gfor_ieee_src))): AM_FCFLAGS += -Wno-unused-dummy-argument -Wno-c-binding-type -ffree-line-length-0 -fallow-leading-underscore -fsignaling-nans
+
+# Add flags for IEEE helper code
+@IEEE_SUPPORT_TRUE@$(patsubst %.c,%.lo,$(notdir $(gfor_ieee_helper_src))): AM_CFLAGS += -fsignaling-nans
 
 # Dependencies between IEEE_ARITHMETIC and IEEE_EXCEPTIONS
 ieee_arithmetic.lo: ieee/ieee_arithmetic.F90 ieee_exceptions.lo
diff --git a/libgfortran/ieee/ieee_helper.c b/libgfortran/ieee/ieee_helper.c
index d70728c..7a103df 100644
--- a/libgfortran/ieee/ieee_helper.c
+++ b/libgfortran/ieee/ieee_helper.c
@@ -25,6 +25,15 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 
 #include "libgfortran.h"
 
+
+/* Check support for issignaling macro.
+   TODO: In the future, provide fallback implementations for IEEE types,
+   because many libc's do not have issignaling yet.  */
+#ifndef issignaling
+# define issignaling(X) 0
+#endif
+
+
 /* Prototypes.  */
 
 extern int ieee_class_helper_4 (GFC_REAL_4 *);
@@ -86,8 +95,10 @@ enum {
  \
     if (res == IEEE_QUIET_NAN) \
     { \
-      /* TODO: Handle signaling NaNs  */ \
-      return res; \
+      if (issignaling (*value)) \
+	return IEEE_SIGNALING_NAN; \
+      else \
+	return IEEE_QUIET_NAN; \
     } \
  \
     return res; \