re PR fortran/40675 (Support -fnosign-zero for SIGN intrinsic for Fortran 77 compatibility)

2009-07-08  Tobias Burnus  <burnus@net-b.de>

        PR fortran/40675
        * simplify.c (gfc_simplify_sign): Handle signed zero correctly.
        * trans-intrinsic.c (gfc_conv_intrinsic_sign): Support
        -fno-sign-zero.
        * invoke.texi (-fno-sign-zero): Add text regarding SIGN
        * intrinsic.

2009-07-08  Tobias Burnus  <burnus@net-b.de>

        PR fortran/40675
        * gfortran.dg/nosigned_zero_1.f90: New test.
        * gfortran.dg/nosigned_zero_2.f90: New test.

From-SVN: r149390

7 files changed, 95 insertions, 11 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 371fdde..77c5f61 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,11 @@
+2009-07-08  Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/40675
+	* simplify.c (gfc_simplify_sign): Handle signed zero correctly.
+	* trans-intrinsic.c (gfc_conv_intrinsic_sign): Support
+	-fno-sign-zero.
+	* invoke.texi (-fno-sign-zero): Add text regarding SIGN intrinsic.
+
 2008-07-08  Paul Thomas  <pault@gcc.gnu.org>
 
 	PR fortran/40591
diff --git a/gcc/fortran/invoke.texi b/gcc/fortran/invoke.texi
index 5d0448f..68cc012 100644
--- a/gcc/fortran/invoke.texi
+++ b/gcc/fortran/invoke.texi
@@ -1024,9 +1024,12 @@ really useful for use by the gfortran testsuite.
 
 @item -fsign-zero
 @opindex @code{fsign-zero}
-When writing zero values, show the negative sign if the sign bit is set.
-@code{fno-sign-zero} does not print the negative sign of zero values for
-compatibility with F77.  Default behavior is to show the negative sign.
+When enabled, floating point numbers of value zero with the sign bit set
+are written as negative number in formatted output and treated as
+negative in the @code{SIGN} intrinsic.  @code{fno-sign-zero} does not
+print the negative sign of zero values and regards zero as positive
+number in the @code{SIGN} intrinsic for compatibility with F77.
+Default behavior is to show the negative sign.
 @end table
 
 @node Code Gen Options
diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index f57f68e..c619f14 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -4957,16 +4957,15 @@ gfc_simplify_sign (gfc_expr *x, gfc_expr *y)
       mpz_abs (result->value.integer, x->value.integer);
       if (mpz_sgn (y->value.integer) < 0)
 	mpz_neg (result->value.integer, result->value.integer);
-
       break;
 
     case BT_REAL:
-      /* TODO: Handle -0.0 and +0.0 correctly on machines that support
-	 it.  */
-      mpfr_abs (result->value.real, x->value.real, GFC_RND_MODE);
-      if (mpfr_sgn (y->value.real) < 0)
-	mpfr_neg (result->value.real, result->value.real, GFC_RND_MODE);
-
+      if (gfc_option.flag_sign_zero)
+	mpfr_copysign (result->value.real, x->value.real, y->value.real,
+		       GFC_RND_MODE);
+      else
+	mpfr_setsign (result->value.real, x->value.real,
+		      mpfr_sgn (y->value.real) < 0 ? 1 : 0, GFC_RND_MODE);
       break;
 
     default:
diff --git a/gcc/fortran/trans-intrinsic.c b/gcc/fortran/trans-intrinsic.c
index dd3b3cd..89b98ec 100644
--- a/gcc/fortran/trans-intrinsic.c
+++ b/gcc/fortran/trans-intrinsic.c
@@ -1263,22 +1263,41 @@ gfc_conv_intrinsic_sign (gfc_se * se, gfc_expr * expr)
   gfc_conv_intrinsic_function_args (se, expr, args, 2);
   if (expr->ts.type == BT_REAL)
     {
+      tree abs;
+
       switch (expr->ts.kind)
 	{
 	case 4:
 	  tmp = built_in_decls[BUILT_IN_COPYSIGNF];
+	  abs = built_in_decls[BUILT_IN_FABSF];
 	  break;
 	case 8:
 	  tmp = built_in_decls[BUILT_IN_COPYSIGN];
+	  abs = built_in_decls[BUILT_IN_FABS];
 	  break;
 	case 10:
 	case 16:
 	  tmp = built_in_decls[BUILT_IN_COPYSIGNL];
+	  abs = built_in_decls[BUILT_IN_FABSL];
 	  break;
 	default:
 	  gcc_unreachable ();
 	}
-      se->expr = build_call_expr (tmp, 2, args[0], args[1]);
+
+      /* We explicitly have to ignore the minus sign. We do so by using
+	 result = (arg1 == 0) ? abs(arg0) : copysign(arg0, arg1).  */
+      if (!gfc_option.flag_sign_zero
+	  && MODE_HAS_SIGNED_ZEROS (TYPE_MODE (TREE_TYPE (args[1]))))
+	{
+	  tree cond, zero;
+	  zero = build_real_from_int_cst (TREE_TYPE (args[1]), integer_zero_node);
+	  cond = fold_build2 (EQ_EXPR, boolean_type_node, args[1], zero);
+	  se->expr = fold_build3 (COND_EXPR, TREE_TYPE (args[0]), cond,
+				  build_call_expr (abs, 1, args[0]),
+				  build_call_expr (tmp, 2, args[0], args[1]));
+	}
+      else
+	se->expr = build_call_expr (tmp, 2, args[0], args[1]);
       return;
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5955370..fa2998a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2009-07-08  Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/40675
+	* gfortran.dg/nosigned_zero_1.f90: New test.
+	* gfortran.dg/nosigned_zero_2.f90: New test.
+
 2009-07-08  Richard Guenther  <rguenther@suse.de>
 
 	* gcc.dg/torture/ssa-pta-fn-1.c: Fix invalid testcase again.
diff --git a/gcc/testsuite/gfortran.dg/nosigned_zero_1.f90 b/gcc/testsuite/gfortran.dg/nosigned_zero_1.f90
new file mode 100644
index 0000000..51ac879
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/nosigned_zero_1.f90
@@ -0,0 +1,24 @@
+! { dg-do run }
+!
+! PR fortran/40675
+!
+! Fortran 77 just had: "The value of a signed zero is the same as
+! the value of an unsigned zero." and g77 returned for SIGN(1.0, -0.0) = 1.0
+!
+! Fortran 95+ has for SIGN: "Case  (iv):  If B is of type real and is zero,
+! then ... (c) If B is negative real zero, the value of the result is -|A|".
+! On architectures, where signed zeros are supported, gfortran's SIGN thus
+! returns for B=-0.0 the -|A|.
+!
+program s
+   x = sign(1.,0.)
+   y = sign(1.,-0.)
+   if (x /=  1.) call abort()
+   if (y /= -1.) call abort()
+   x = 1.
+   y = 0.
+   x = sign(x, y)
+   y = sign(x, -y)
+   if (x /=  1.) call abort()
+   if (y /= -1.) call abort()
+end program s
diff --git a/gcc/testsuite/gfortran.dg/nosigned_zero_2.f90 b/gcc/testsuite/gfortran.dg/nosigned_zero_2.f90
new file mode 100644
index 0000000..af05574
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/nosigned_zero_2.f90
@@ -0,0 +1,25 @@
+! { dg-do run }
+! { dg-options "-fno-sign-zero" }
+!
+! PR fortran/40675
+!
+! Fortran 77 just had: "The value of a signed zero is the same as
+! the value of an unsigned zero." and g77 returned for SIGN(1.0, -0.0) = 1.0
+!
+! Fortran 95+ has for SIGN: "Case  (iv):  If B is of type real and is zero,
+! then ... (c) If B is negative real zero, the value of the result is -|A|".
+! On architectures, where signed zeros are supported, gfortran's SIGN thus
+! returns for B=-0.0 the -|A|.
+!
+program s
+   x = sign(1.,0.)
+   y = sign(1.,-0.)
+   if (x /= 1.) call abort()
+   if (y /= 1.) call abort()
+   x = 1.
+   y = 0.
+   x = sign(x, y)
+   y = sign(x, -y)
+   if (x /= 1.) call abort()
+   if (y /= 1.) call abort()
+end program s