arith.c (arith_power): If simplifying integer power expression to zero...

2017-01-23  Thomas Koenig  <tkoenig@netcologne.de>

	* arith.c (arith_power):  If simplifying integer power expression
	to zero, warn if -Winteger-division is given.

2017-01-23  Thomas Koenig  <tkoenig@netcologne.de>

	* gfortran.dg/integer_exponentiation_7.f90:  New test.

From-SVN: r244830

gcc/fortran/ChangeLog

+2017-01-23  Thomas Koenig  <tkoenig@netcologne.de>
+
+	* arith.c (arith_power):  If simplifying integer power expression
+	to zero, warn if -Winteger-division is given.
+
 2017-01-22  Jakub Jelinek  <jakub@redhat.com>
 
 	PR fortran/79154

gcc/fortran/arith.c

@@ -874,6 +874,10 @@ arith_power (gfc_expr *op1, gfc_expr *op2, gfc_expr **resultp)
 		  {
 		    /* if op2 < 0, op1**op2 == 0  because abs(op1) > 1.  */
 		    mpz_set_si (result->value.integer, 0);
+		    if (warn_integer_division)
+		      gfc_warning_now (OPT_Winteger_division, "Negative "
+				       "exponent of integer has zero "
+				       "result at %L", &result->where);
 		  }
 		else if (gfc_extract_int (op2, &power))
 		  {

gcc/testsuite/ChangeLog

+2017-01-23  Thomas Koenig  <tkoenig@netcologne.de>
+
+	* gfortran.dg/integer_exponentiation_7.f90:  New test.
+
 2017-01-23  Bernd Schmidt  <bschmidt@redhat.com>
 
 	PR rtl-optimization/78634

gcc/testsuite/gfortran.dg/integer_exponentiation_7.f90

+! { dg-do compile }
+! { dg-options "-Winteger-division" }
+program main
+  print *,10**(-3) ! { dg-warning "Negative exponent of integer has zero result" }
+end program main