[patch, fortran] Fix for modulo checking similar to PR86045

[Jerry DeLisle <jvdelisle at charter dot net>]

Hi all,

Similar to Steve's fix of 'mod' checking for 86045, the attached patch 
fixes an ICE in 'modulo' when P = 0.

Mark pointed this out and greatly assisted with the patch.  I have 
regression tested and plan to commit to trunk, 8, and 7 so that we are 
in sync with the 'mod' patch.

If no objections, later today I will commit with the test case.

Regards,

Jerry

2018-09-03  Jerry DeLisle  <jvdelisle@gcc.gnu.org>

	* simplify.c (gfc_simplify_modulo): Re-arrange code to test
 	whether	'P' is zero and issue an error if it is.


diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index 41997367cf9..d35bbbaaa1b 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -5525,54 +5525,57 @@ gfc_simplify_modulo (gfc_expr *a, gfc_expr *p)
   gfc_expr *result;
   int kind;
 
-  if (a->expr_type != EXPR_CONSTANT || p->expr_type != EXPR_CONSTANT)
+  /* First check p.  */
+  if (p->expr_type != EXPR_CONSTANT)
     return NULL;
 
-  kind = a->ts.kind > p->ts.kind ? a->ts.kind : p->ts.kind;
-  result = gfc_get_constant_expr (a->ts.type, kind, &a->where);
-
-  switch (a->ts.type)
+  /* p shall not be 0.  */
+  switch (p->ts.type)
     {
       case BT_INTEGER:
 	if (mpz_cmp_ui (p->value.integer, 0) == 0)
 	  {
-	    /* Result is processor-dependent. This processor just opts
-	      to not handle it at all.  */
-	    gfc_error ("Second argument of MODULO at %L is zero", &a->where);
-	    gfc_free_expr (result);
+	    gfc_error ("Argument %qs of MODULO at %L shall not be zero",
+			"P", &p->where);
 	    return &gfc_bad_expr;
 	  }
-	mpz_fdiv_r (result->value.integer, a->value.integer, p->value.integer);
-
 	break;
-
       case BT_REAL:
 	if (mpfr_cmp_ui (p->value.real, 0) == 0)
 	  {
-	    /* Result is processor-dependent.  */
-	    gfc_error ("Second argument of MODULO at %L is zero", &p->where);
-	    gfc_free_expr (result);
+	    gfc_error ("Argument %qs of MODULO at %L shall not be zero",
+			"P", &p->where);
 	    return &gfc_bad_expr;
 	  }
-
-	gfc_set_model_kind (kind);
-	mpfr_fmod (result->value.real, a->value.real, p->value.real,
-		   GFC_RND_MODE);
-	if (mpfr_cmp_ui (result->value.real, 0) != 0)
-	  {
-	    if (mpfr_signbit (a->value.real) != mpfr_signbit (p->value.real))
-	      mpfr_add (result->value.real, result->value.real, p->value.real,
-			GFC_RND_MODE);
-	  }
-	else
-	  mpfr_copysign (result->value.real, result->value.real,
-			 p->value.real, GFC_RND_MODE);
 	break;
-
       default:
 	gfc_internal_error ("gfc_simplify_modulo(): Bad arguments");
     }
 
+  if (a->expr_type != EXPR_CONSTANT)
+    return NULL;
+
+  kind = a->ts.kind > p->ts.kind ? a->ts.kind : p->ts.kind;
+  result = gfc_get_constant_expr (a->ts.type, kind, &a->where);
+
+  if (a->ts.type == BT_INTEGER)
+	mpz_fdiv_r (result->value.integer, a->value.integer, p->value.integer);
+  else
+    {
+      gfc_set_model_kind (kind);
+      mpfr_fmod (result->value.real, a->value.real, p->value.real,
+                 GFC_RND_MODE);
+      if (mpfr_cmp_ui (result->value.real, 0) != 0)
+        {
+          if (mpfr_signbit (a->value.real) != mpfr_signbit (p->value.real))
+            mpfr_add (result->value.real, result->value.real, p->value.real,
+                      GFC_RND_MODE);
+	    }
+	  else
+        mpfr_copysign (result->value.real, result->value.real,
+                       p->value.real, GFC_RND_MODE);
+    }
+
   return range_check (result, "MODULO");
 }
 
diff --git a/gcc/testsuite/gfortran.dg/modulo_check.f90 b/gcc/testsuite/gfortran.dg/modulo_check.f90
new file mode 100644
index 00000000000..8819a2f8e4e
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/modulo_check.f90
@@ -0,0 +1,8 @@
+! { dg-do compile }
+! Test checks on modulo with p == 0
+program p
+   logical :: a(2) = (modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
+   integer :: b = count(modulo([2,3],0) == 0)   ! { dg-error "shall not be zero" }
+   integer :: c = all(modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
+   integer :: d = any(modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
+end program

! { dg-do compile }
! Test checks on modulo with p == 0
program p
   logical :: a(2) = (modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
   integer :: b = count(modulo([2,3],0) == 0)   ! { dg-error "shall not be zero" }
   integer :: c = all(modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
   integer :: d = any(modulo([2,3],0) == 0)     ! { dg-error "shall not be zero" }
end program