re PR fortran/45159 (Unnecessary temporaries)

2010-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/45159
	* dependency.c (check_section_vs_section):  Pre-calculate
	the relationship between the strides and the relationship
	between the start values.  Use an integer constant one for
	that purpose.
	Forward dependencies for positive strides apply for where
	the lhs start <= rhs start and lhs stride <= rhs stride
	and vice versa for negative stride.  No need to compare
	end expressions in either case (assume no bounds violation).

2010-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/45159
	* gfortran.dg/dependency_38.f90:  New test.

From-SVN: r167413

4 files changed, 81 insertions, 47 deletions

diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index ae2f033..36b2ef2 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,5 +1,17 @@
 2010-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
+	PR fortran/45159
+	* dependency.c (check_section_vs_section):  Pre-calculate
+	the relationship between the strides and the relationship
+	between the start values.  Use an integer constant one for
+	that purpose.
+	Forward dependencies for positive strides apply for where
+	the lhs start <= rhs start and lhs stride <= rhs stride
+	and vice versa for negative stride.  No need to compare
+	end expressions in either case (assume no bounds violation).
+
+2010-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
 	* trans-array.c (gfc_could_be_alias):  Handle BT_CLASS
 	as well as BT_DERIVED.
 	(gfc_array_allocate):  Likewise.
diff --git a/gcc/fortran/dependency.c b/gcc/fortran/dependency.c
index 40969f6..77e8df7 100644
--- a/gcc/fortran/dependency.c
+++ b/gcc/fortran/dependency.c
@@ -1071,8 +1071,10 @@ check_section_vs_section (gfc_array_ref *l_ar, gfc_array_ref *r_ar, int n)
   gfc_expr *r_stride;
   gfc_expr *r_lower;
   gfc_expr *r_upper;
+  gfc_expr *one_expr;
   int r_dir;
-  bool identical_strides;
+  int stride_comparison;
+  int start_comparison;
 
   /* If they are the same range, return without more ado.  */
   if (gfc_is_same_range (l_ar, r_ar, n, 0))
@@ -1126,22 +1128,24 @@ check_section_vs_section (gfc_array_ref *l_ar, gfc_array_ref *r_ar, int n)
   if (l_dir == 0 || r_dir == 0)
     return GFC_DEP_OVERLAP;
 
-  /* Determine if the strides are equal.  */
+  /* Determine the relationship between the strides.  Set stride_comparison to
+     -2 if the dependency cannot be determined
+     -1 if l_stride < r_stride
+      0 if l_stride == r_stride
+      1 if l_stride > r_stride
+     as determined by gfc_dep_compare_expr.  */
 
-  if (l_stride)
-    {
-      if (r_stride)
-	identical_strides = gfc_dep_compare_expr (l_stride, r_stride) == 0;
-      else
-	identical_strides = gfc_expr_is_one (l_stride, 0) == 1;
-    }
+  one_expr = gfc_get_int_expr (gfc_index_integer_kind, NULL, 1);
+
+  stride_comparison = gfc_dep_compare_expr (l_stride ? l_stride : one_expr,
+					    r_stride ? r_stride : one_expr);
+
+  if (l_start && r_start)
+    start_comparison = gfc_dep_compare_expr (l_start, r_start);
   else
-    {
-      if (r_stride)
-	identical_strides = gfc_expr_is_one (r_stride, 0) == 1;
-      else
-	identical_strides = true;
-    }
+    start_comparison = -2;
+      
+  gfc_free (one_expr);
 
   /* Determine LHS upper and lower bounds.  */
   if (l_dir == 1)
@@ -1237,61 +1241,60 @@ check_section_vs_section (gfc_array_ref *l_ar, gfc_array_ref *r_ar, int n)
 
 #undef IS_CONSTANT_INTEGER
 
-  /* Check for forward dependencies x:y vs. x+1:z.  */
-  if (l_dir == 1 && r_dir == 1
-      && l_start && r_start && gfc_dep_compare_expr (l_start, r_start) == -1
-      && l_end && r_end && gfc_dep_compare_expr (l_end, r_end) == -1)
-    {
-      if (identical_strides)
-	return GFC_DEP_FORWARD;
-    }
+  /* Check for forward dependencies x:y vs. x+1:z and x:y:z vs. x:y:z+1. */
 
-  /* Check for forward dependencies x:y:-1 vs. x-1:z:-1.  */
-  if (l_dir == -1 && r_dir == -1
-      && l_start && r_start && gfc_dep_compare_expr (l_start, r_start) == 1
-      && l_end && r_end && gfc_dep_compare_expr (l_end, r_end) == 1)
-    {
-      if (identical_strides)
-	return GFC_DEP_FORWARD;
-    }
+  if (l_dir == 1 && r_dir == 1 &&
+      (start_comparison == 0 || start_comparison == -1)
+      && (stride_comparison == 0 || stride_comparison == -1))
+	  return GFC_DEP_FORWARD;
 
+  /* Check for forward dependencies x:y:-1 vs. x-1:z:-1 and
+     x:y:-1 vs. x:y:-2.  */
+  if (l_dir == -1 && r_dir == -1 && 
+      (start_comparison == 0 || start_comparison == 1)
+      && (stride_comparison == 0 || stride_comparison == 1))
+    return GFC_DEP_FORWARD;
 
-  if (identical_strides)
+  if (stride_comparison == 0 || stride_comparison == -1)
     {
-
       if (l_start && IS_ARRAY_EXPLICIT (l_ar->as))
 	{
 
-	  /* Check for a(low:y:s) vs. a(z:a:s) where a has a lower bound
+	  /* Check for a(low:y:s) vs. a(z:x:s) or
+	     a(low:y:s) vs. a(z:x:s+1) where a has a lower bound
 	     of low, which is always at least a forward dependence.  */
 
 	  if (r_dir == 1
 	      && gfc_dep_compare_expr (l_start, l_ar->as->lower[n]) == 0)
 	    return GFC_DEP_FORWARD;
+	}
+    }
 
-	  /* Check for a(high:y:-s) vs. a(z:a:-s) where a has a higher bound
+  if (stride_comparison == 0 || stride_comparison == 1)
+    {
+      if (l_start && IS_ARRAY_EXPLICIT (l_ar->as))
+	{
+      
+	  /* Check for a(high:y:-s) vs. a(z:x:-s) or
+	     a(high:y:-s vs. a(z:x:-s-1) where a has a higher bound
 	     of high, which is always at least a forward dependence.  */
 
 	  if (r_dir == -1
 	      && gfc_dep_compare_expr (l_start, l_ar->as->upper[n]) == 0)
 	    return GFC_DEP_FORWARD;
 	}
+    }
 
+
+  if (stride_comparison == 0)
+    {
       /* From here, check for backwards dependencies.  */
-      /* x:y vs. x+1:z.  */
-      if (l_dir == 1 && r_dir == 1
-	    && l_start && r_start
-	    && gfc_dep_compare_expr (l_start, r_start) == 1
-	    && l_end && r_end
-	    && gfc_dep_compare_expr (l_end, r_end) == 1)
+      /* x+1:y vs. x:z.  */
+      if (l_dir == 1 && r_dir == 1  && start_comparison == 1)
 	return GFC_DEP_BACKWARD;
 
-      /* x:y:-1 vs. x-1:z:-1.  */
-      if (l_dir == -1 && r_dir == -1
-	    && l_start && r_start
-	    && gfc_dep_compare_expr (l_start, r_start) == -1
-	    && l_end && r_end
-	    && gfc_dep_compare_expr (l_end, r_end) == -1)
+      /* x-1:y:-1 vs. x:z:-1.  */
+      if (l_dir == -1 && r_dir == -1 && start_comparison == -1)
 	return GFC_DEP_BACKWARD;
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e0769f5..10295b2 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2010-12-02  Thomas Koenig  <tkoenig@gcc.gnu.org>
+
+	PR fortran/45159
+	* gfortran.dg/dependency_38.f90:  New test.
+
 2010-12-02  Ian Lance Taylor  <iant@google.com>
 
 	* lib/go.exp: New file.
diff --git a/gcc/testsuite/gfortran.dg/dependency_38.f90 b/gcc/testsuite/gfortran.dg/dependency_38.f90
new file mode 100644
index 0000000..60cb2ad
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/dependency_38.f90
@@ -0,0 +1,14 @@
+! { dg-do compile }
+! { dg-options "-Warray-temporaries" }
+! PR 45159 - No temporary should be created for this.
+program main
+  integer a(100)
+  a(10:16:2) = a(10:16:2)
+  a(10:16:2) = a(10:19:3)
+  a(10:18:2) = a(12:20:2)
+  a(1:10) = a(2:20:2)
+  a(16:10:-2) = a(16:10:-2)
+  a(19:10:-1) = a(19:1:-2)
+  a(19:10:-1) = a(18:9:-1)
+  a(19:11:-1) = a(18:2:-2)
+end program main