2009-03-28 Tobias Burnus <burnus@net-b.de>

        PR fortran/38432
        * resolve.c (gfc_resolve_iterator): Add zero-loop warning.

2009-03-28  Tobias Burnus  <burnus@net-b.de>

        PR fortran/38432
        * gfortran.dg/do_check_5.f90: New test.
        * gfortran.dg/array_constructor_11.f90: Add dg-warning.
        * gfortran.dg/array_constructor_18.f90: Ditto.
        * gfortran.dg/array_constructor_22.f90: Ditto.
        * gfortran.dg/do_3.F90: Ditto.
        * gfortran.dg/do_1.f90: Ditto.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@145186 138bc75d-0d04-0410-961f-82ee72b054a4

9 files changed, 91 insertions, 24 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index 28fa7ca892d..e3bacc1aa0f 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,8 @@
+2009-03-28  Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/38432
+	* resolve.c (gfc_resolve_iterator): Add zero-loop warning.
+
 2009-03-28  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
 	    Paul Thomas  <pault@gcc.gnu.org>
 	    Tobias Burnus  <burnus@net-b.de>
diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index e887fb13a6f..1d6ee852426 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -4918,6 +4918,26 @@ gfc_resolve_iterator (gfc_iterator *iter, bool real_ok)
       || iter->step->ts.type != iter->var->ts.type)
     gfc_convert_type (iter->step, &iter->var->ts, 2);
 
+  if (iter->start->expr_type == EXPR_CONSTANT
+      && iter->end->expr_type == EXPR_CONSTANT
+      && iter->step->expr_type == EXPR_CONSTANT)
+    {
+      int sgn, cmp;
+      if (iter->start->ts.type == BT_INTEGER)
+	{
+	  sgn = mpz_cmp_ui (iter->step->value.integer, 0);
+	  cmp = mpz_cmp (iter->end->value.integer, iter->start->value.integer);
+	}
+      else
+	{
+	  sgn = mpfr_sgn (iter->step->value.real);
+	  cmp = mpfr_cmp (iter->end->value.real, iter->start->value.real);
+	}
+      if ((sgn > 0 && cmp < 0) || (sgn < 0 && cmp > 0))
+	gfc_warning ("DO loop at %L will be executed zero times",
+		     &iter->step->where);
+    }
+
   return SUCCESS;
 }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a2e329e1de3..315f6cfc06f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,13 @@
+2009-03-28 Tobias Burnus  <burnus@net-b.de>
+
+	PR fortran/38432
+	* gfortran.dg/do_check_5.f90: New test.
+	* gfortran.dg/array_constructor_11.f90: Add dg-warning.
+	* gfortran.dg/array_constructor_18.f90: Ditto.
+	* gfortran.dg/array_constructor_22.f90: Ditto.
+	* gfortran.dg/do_3.F90: Ditto.
+	* gfortran.dg/do_1.f90: Ditto.
+
 2009-03-28  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/38180
diff --git a/gcc/testsuite/gfortran.dg/array_constructor_11.f90 b/gcc/testsuite/gfortran.dg/array_constructor_11.f90
index 395d2927b9e..bb9f0dddb11 100644
--- a/gcc/testsuite/gfortran.dg/array_constructor_11.f90
+++ b/gcc/testsuite/gfortran.dg/array_constructor_11.f90
@@ -10,20 +10,20 @@ contains
 
     call test (1, 11, 3, (/ (i, i = 1, 11, 3) /))
     call test (3, 20, 2, (/ (i, i = 3, 20, 2) /))
-    call test (4, 0, 11, (/ (i, i = 4, 0, 11) /))
+    call test (4, 0, 11, (/ (i, i = 4, 0, 11) /)) ! { dg-warning "will be executed zero times" }
 
     call test (110, 10, -3,  (/ (i, i = 110, 10, -3) /))
     call test (200, 20, -12, (/ (i, i = 200, 20, -12) /))
-    call test (29, 30, -6,   (/ (i, i = 29, 30, -6) /))
+    call test (29, 30, -6,   (/ (i, i = 29, 30, -6) /)) ! { dg-warning "will be executed zero times" }
 
     call test (1, order, 3,  (/ (i, i = 1, order, 3) /))
     call test (order, 1, -3, (/ (i, i = order, 1, -3) /))
 
     ! Triggers compile-time iterator calculations in trans-array.c
     call test (1, 1000, 2,   (/ (i, i = 1, 1000, 2),   (i, i = order, 0, 1) /))
-    call test (1, 0, 3,      (/ (i, i = 1, 0, 3),      (i, i = order, 0, 1) /))
-    call test (1, 2000, -5,  (/ (i, i = 1, 2000, -5),  (i, i = order, 0, 1) /))
-    call test (3000, 99, 4,  (/ (i, i = 3000, 99, 4),  (i, i = order, 0, 1) /))
+    call test (1, 0, 3,      (/ (i, i = 1, 0, 3),      (i, i = order, 0, 1) /)) ! { dg-warning "will be executed zero times" }
+    call test (1, 2000, -5,  (/ (i, i = 1, 2000, -5),  (i, i = order, 0, 1) /)) ! { dg-warning "will be executed zero times" }
+    call test (3000, 99, 4,  (/ (i, i = 3000, 99, 4),  (i, i = order, 0, 1) /)) ! { dg-warning "will be executed zero times" }
     call test (400, 77, -39, (/ (i, i = 400, 77, -39), (i, i = order, 0, 1) /))
 
     do j = -10, 10
diff --git a/gcc/testsuite/gfortran.dg/array_constructor_18.f90 b/gcc/testsuite/gfortran.dg/array_constructor_18.f90
index 246f448063c..c78976839d0 100644
--- a/gcc/testsuite/gfortran.dg/array_constructor_18.f90
+++ b/gcc/testsuite/gfortran.dg/array_constructor_18.f90
@@ -5,7 +5,7 @@
 !
 ! Contributed by Joost VandeVondele <jv244@cam.ac.uk>
 !
-  call foo ((/(S1(i),i=1,3,-1)/))
+  call foo ((/(S1(i),i=1,3,-1)/)) ! { dg-warning "will be executed zero times" }
 CONTAINS
   FUNCTION S1(i)
     CHARACTER(LEN=1) :: S1
diff --git a/gcc/testsuite/gfortran.dg/array_constructor_22.f90 b/gcc/testsuite/gfortran.dg/array_constructor_22.f90
index d29039a80e6..0dcdaea68c1 100644
--- a/gcc/testsuite/gfortran.dg/array_constructor_22.f90
+++ b/gcc/testsuite/gfortran.dg/array_constructor_22.f90
@@ -7,7 +7,7 @@ module test
       function my_string(x) 
          integer i 
          real, intent(in) :: x(:) 
-         character(0) h4(1:minval([(1,i=1,0)],1)) 
+         character(0) h4(1:minval([(1,i=1,0)],1)) ! { dg-warning "will be executed zero times" }
          character(0) sv1(size(x,1):size(h4)) 
          character(0) sv2(2*lbound(sv1,1):size(h4)) 
          character(lbound(sv2,1)-3) my_string 
diff --git a/gcc/testsuite/gfortran.dg/do_1.f90 b/gcc/testsuite/gfortran.dg/do_1.f90
index 20e1f31ca67..171275af3f2 100644
--- a/gcc/testsuite/gfortran.dg/do_1.f90
+++ b/gcc/testsuite/gfortran.dg/do_1.f90
@@ -29,17 +29,17 @@ program do_1
 
   ! Zero iterations
   j = 0
-  do i = 1, 0, 1
+  do i = 1, 0, 1 ! { dg-warning "executed zero times" }
     j = j + 1
   end do
   if (j .ne. 0) call abort
   j = 0
-  do i = 1, 0, 2
+  do i = 1, 0, 2 ! { dg-warning "executed zero times" }
     j = j + 1
   end do
   if (j .ne. 0) call abort
   j = 0
-  do i = 1, 2, -1
+  do i = 1, 2, -1 ! { dg-warning "executed zero times" }
     j = j + 1
   end do
   if (j .ne. 0) call abort
diff --git a/gcc/testsuite/gfortran.dg/do_3.F90 b/gcc/testsuite/gfortran.dg/do_3.F90
index 3cada5a0051..67723a508f4 100644
--- a/gcc/testsuite/gfortran.dg/do_3.F90
+++ b/gcc/testsuite/gfortran.dg/do_3.F90
@@ -21,16 +21,16 @@ program test
   TEST_LOOP(i, 0, 1, 2, 1, test_i, 2)
   TEST_LOOP(i, 0, 1, 3, 1, test_i, 3)
   TEST_LOOP(i, 0, 1, huge(0), 1, test_i, huge(0))
-  TEST_LOOP(i, 0, 1, -1, 0, test_i, 0)
-  TEST_LOOP(i, 0, 1, -2, 0, test_i, 0)
-  TEST_LOOP(i, 0, 1, -3, 0, test_i, 0)
-  TEST_LOOP(i, 0, 1, -huge(0), 0, test_i, 0)
-  TEST_LOOP(i, 0, 1, -huge(0)-1, 0, test_i, 0)
-
-  TEST_LOOP(i, 1, 0, 1, 0, test_i, 1)
-  TEST_LOOP(i, 1, 0, 2, 0, test_i, 1)
-  TEST_LOOP(i, 1, 0, 3, 0, test_i, 1)
-  TEST_LOOP(i, 1, 0, huge(0), 0, test_i, 1)
+  TEST_LOOP(i, 0, 1, -1, 0, test_i, 0) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 0, 1, -2, 0, test_i, 0) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 0, 1, -3, 0, test_i, 0) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 0, 1, -huge(0), 0, test_i, 0) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 0, 1, -huge(0)-1, 0, test_i, 0) ! { dg-warning "executed zero times" }
+
+  TEST_LOOP(i, 1, 0, 1, 0, test_i, 1) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 1, 0, 2, 0, test_i, 1) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 1, 0, 3, 0, test_i, 1) ! { dg-warning "executed zero times" }
+  TEST_LOOP(i, 1, 0, huge(0), 0, test_i, 1) ! { dg-warning "executed zero times" }
   TEST_LOOP(i, 1, 0, -1, 2, test_i, -1)
   TEST_LOOP(i, 1, 0, -2, 1, test_i, -1)
   TEST_LOOP(i, 1, 0, -3, 1, test_i, -2)
@@ -58,14 +58,14 @@ program test
   TEST_LOOP(i1, huge(i1), -huge(i1)-1_1, -huge(i1)-1_1, 2, test_i1, -huge(i1)-2_1)
 
   TEST_LOOP(i1, -2_1, 3_1, huge(i1), 1, test_i1, huge(i1)-2_1)
-  TEST_LOOP(i1, -2_1, 3_1, -huge(i1), 0, test_i1, -2_1)
+  TEST_LOOP(i1, -2_1, 3_1, -huge(i1), 0, test_i1, -2_1) ! { dg-warning "executed zero times" }
   TEST_LOOP(i1, 2_1, -3_1, -huge(i1), 1, test_i1, 2_1-huge(i1))
-  TEST_LOOP(i1, 2_1, -3_1, huge(i1), 0, test_i1, 2_1)
+  TEST_LOOP(i1, 2_1, -3_1, huge(i1), 0, test_i1, 2_1) ! { dg-warning "executed zero times" }
 
   ! Real loops
   TEST_LOOP(r, 0.0, 1.0, 0.11, 1 + int(1.0/0.11), test_r, 0.0)
-  TEST_LOOP(r, 0.0, 1.0, -0.11, 0, test_r, 0.0)
-  TEST_LOOP(r, 0.0, -1.0, 0.11, 0, test_r, 0.0)
+  TEST_LOOP(r, 0.0, 1.0, -0.11, 0, test_r, 0.0) ! { dg-warning "executed zero times" }
+  TEST_LOOP(r, 0.0, -1.0, 0.11, 0, test_r, 0.0) ! { dg-warning "executed zero times" }
   TEST_LOOP(r, 0.0, -1.0, -0.11, 1 + int(1.0/0.11), test_r, 0.0)
   TEST_LOOP(r, 0.0, 0.0, 0.11, 1, test_r, 0.0)
   TEST_LOOP(r, 0.0, 0.0, -0.11, 1, test_r, 0.0)
diff --git a/gcc/testsuite/gfortran.dg/do_check_5.f90 b/gcc/testsuite/gfortran.dg/do_check_5.f90
new file mode 100644
index 00000000000..081a228cfc7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/do_check_5.f90
@@ -0,0 +1,32 @@
+! { dg-do compile }
+! 
+! PR/fortran 38432
+! DO-loop compile-time checks
+!
+implicit none
+integer :: i
+real :: r
+do i = 1, 0 ! { dg-warning "executed zero times" }
+end do
+
+do i = 1, -1, 1 ! { dg-warning "executed zero times" }
+end do
+
+do i = 1, 2, -1 ! { dg-warning "executed zero times" }
+end do
+
+do i = 1, 2, 0 ! { dg-error "cannot be zero" }
+end do
+
+do r = 1, 0 ! { dg-warning "must be integer|executed zero times" }
+end do
+
+do r = 1, -1, 1 ! { dg-warning "must be integer|executed zero times" }
+end do
+
+do r = 1, 2, -1 ! { dg-warning "must be integer|executed zero times" }
+end do
+
+do r = 1, 2, 0 ! { dg-error "must be integer|cannot be zero" }
+end do
+end