tree-dfa.c (get_ref_base_and_extent): Use range-info to refine results when processing array refs with variable index.

2018-05-18  Richard Biener  <rguenther@suse.de>

	* tree-dfa.c (get_ref_base_and_extent): Use range-info to refine
	results when processing array refs with variable index.

	* gcc.dg/tree-ssa/ssa-dse-35.c: New testcase.
	* gcc.dg/graphite/scop-10.c: Adjust to avoid dead code.
	* gcc.dg/graphite/scop-6.c: Likewise.
	* gcc.dg/graphite/scop-7.c: Likewise.
	* gcc.dg/graphite/scop-8.c: Likewise.
	* gcc.dg/graphite/scop-9.c: Likewise.

From-SVN: r260354

9 files changed, 75 insertions, 5 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3026df4..8a1bc05 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2018-05-18  Richard Biener  <rguenther@suse.de>
+
+	* tree-dfa.c (get_ref_base_and_extent): Use range-info to refine
+	results when processing array refs with variable index.
+
 2018-05-18  Toon Moene  <toon@moene.org>
 
 	* doc/invoke.texi: Move -floop-unroll-and-jam documentation
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 840d9a0..7d53f32 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2018-05-18  Richard Biener  <rguenther@suse.de>
+
+	* gcc.dg/tree-ssa/ssa-dse-35.c: New testcase.
+	* gcc.dg/graphite/scop-10.c: Adjust to avoid dead code.
+	* gcc.dg/graphite/scop-6.c: Likewise.
+	* gcc.dg/graphite/scop-7.c: Likewise.
+	* gcc.dg/graphite/scop-8.c: Likewise.
+	* gcc.dg/graphite/scop-9.c: Likewise.
+
 2018-05-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* gcc.target/aarch64/vect-init-ld1.c: New test.
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-10.c b/gcc/testsuite/gcc.dg/graphite/scop-10.c
index 20d5351..d041830 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-10.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-10.c
@@ -22,7 +22,7 @@ int toto()
         b[i+k] = b[i+k-5] + 2;
     }
 
-  return a[3][5] + b[1];
+  return a[3][5] + b[2];
 }
 
 /* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-6.c b/gcc/testsuite/gcc.dg/graphite/scop-6.c
index 1da486a..9bc1d9f 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-6.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-6.c
@@ -23,7 +23,7 @@ int toto()
         b[i+k] = b[i+k-5] + 2;
     }
 
-  return a[3][5] + b[1];
+  return a[3][5] + b[2];
 }
 
 /* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-7.c b/gcc/testsuite/gcc.dg/graphite/scop-7.c
index 2f0a504..f4f3093f 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-7.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-7.c
@@ -23,7 +23,7 @@ int toto()
         b[i+k] = b[i+k-5] + 2;
     }
 
-  return a[3][5] + b[1];
+  return a[3][5] + b[2];
 }
 
 /* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-8.c b/gcc/testsuite/gcc.dg/graphite/scop-8.c
index 3ceb5d8..b062651 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-8.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-8.c
@@ -23,7 +23,7 @@ int toto()
         b[i+k] = b[i+k-5] + 2;
     }
 
-  return a[3][5] + b[1];
+  return a[3][5] + b[2];
 }
 
 /* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/graphite/scop-9.c b/gcc/testsuite/gcc.dg/graphite/scop-9.c
index 9388872..b19291b 100644
--- a/gcc/testsuite/gcc.dg/graphite/scop-9.c
+++ b/gcc/testsuite/gcc.dg/graphite/scop-9.c
@@ -18,7 +18,7 @@ int toto()
         b[i+k] = b[i+k-5] + 2;
     }
 
-  return a[3][5] + b[1];
+  return a[3][5] + b[2];
 }
 
 /* { dg-final { scan-tree-dump-times "number of SCoPs: 1" 1 "graphite"} } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c
new file mode 100644
index 0000000..1f21670
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-dse-35.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-dse1-details" } */
+
+int a[256];
+void foo (void)
+{
+  a[0] = 1;
+  for (int i = 5; i < 17; ++i)
+    a[i] = i;
+  a[0] = 2;
+}
+
+/* { dg-final { scan-tree-dump-times "Deleted dead store" 1 "dse1" } } */
diff --git a/gcc/tree-dfa.c b/gcc/tree-dfa.c
index a121b88..00aa75f 100644
--- a/gcc/tree-dfa.c
+++ b/gcc/tree-dfa.c
@@ -529,6 +529,49 @@ get_ref_base_and_extent (tree exp, poly_int64_pod *poffset,
 		/* Remember that we have seen an array ref with a variable
 		   index.  */
 		seen_variable_array_ref = true;
+
+		wide_int min, max;
+		if (TREE_CODE (index) == SSA_NAME
+		    && (low_bound = array_ref_low_bound (exp),
+			poly_int_tree_p (low_bound))
+		    && (unit_size = array_ref_element_size (exp),
+			TREE_CODE (unit_size) == INTEGER_CST)
+		    && get_range_info (index, &min, &max) == VR_RANGE)
+		  {
+		    poly_offset_int lbound = wi::to_poly_offset (low_bound);
+		    /* Try to constrain maxsize with range information.  */
+		    offset_int omax
+		      = offset_int::from (max, TYPE_SIGN (TREE_TYPE (index)));
+		    if (known_lt (lbound, omax))
+		      {
+			poly_offset_int rmaxsize;
+			rmaxsize = (omax - lbound + 1)
+			    * wi::to_offset (unit_size) << LOG2_BITS_PER_UNIT;
+			if (!known_size_p (maxsize)
+			    || known_lt (rmaxsize, maxsize))
+			  {
+			    /* If we know an upper bound below the declared
+			       one this is no longer variable.  */
+			    if (known_size_p (maxsize))
+			      seen_variable_array_ref = false;
+			    maxsize = rmaxsize;
+			  }
+		      }
+		    /* Try to adjust bit_offset with range information.  */
+		    offset_int omin
+		      = offset_int::from (min, TYPE_SIGN (TREE_TYPE (index)));
+		    if (known_le (lbound, omin))
+		      {
+			poly_offset_int woffset
+			  = wi::sext (omin - lbound,
+				      TYPE_PRECISION (TREE_TYPE (index)));
+			woffset *= wi::to_offset (unit_size);
+			woffset <<= LOG2_BITS_PER_UNIT;
+			bit_offset += woffset;
+			if (known_size_p (maxsize))
+			  maxsize -= woffset;
+		      }
+		  }
 	      }
 	  }
 	  break;