Equate MEM_REFs and ARRAY_REFs in tree-ssa-scopedtables.c

PR target/63679

gcc/:

	* tree-ssa-scopedtables.c (avail_expr_hash): Hash MEM_REF and ARRAY_REF
	using get_ref_base_and_extent.
	(equal_mem_array_ref_p): New.
	(hashable_expr_equal_p): Add call to previous.

gcc/testsuite/:

        * gcc.dg/tree-ssa/ssa-dom-cse-5.c: New.
        * gcc.dg/tree-ssa/ssa-dom-cse-6.c: New.
        * gcc.dg/tree-ssa/ssa-dom-cse-7.c: New.

From-SVN: r232508

gcc/ChangeLog

@@ -1,3 +1,11 @@
+2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
+
+	PR target/63679
+	* tree-ssa-scopedtables.c (avail_expr_hash): Hash MEM_REF and ARRAY_REF
+	using get_ref_base_and_extent.
+	(equal_mem_array_ref_p): New.
+	(hashable_expr_equal_p): Add call to previous.
+
 2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
 
 	PR target/63679

gcc/testsuite/ChangeLog

@@ -1,3 +1,10 @@
+2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
+
+	PR target/63679
+	* gcc.dg/tree-ssa/ssa-dom-cse-5.c: New.
+	* gcc.dg/tree-ssa/ssa-dom-cse-6.c: New.
+	* gcc.dg/tree-ssa/ssa-dom-cse-7.c: New.
+
 2016-01-18  Alan Lawrence  <alan.lawrence@arm.com>
 
 	PR target/63679

gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-cse-5.c

@@ -0,0 +1,18 @@
+/* Test normalization of ARRAY_REF expressions to MEM_REFs in dom.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-fre -fdump-tree-dom2" } */
+
+#define N 8
+
+int
+main (int argc, char **argv)
+{
+  int a[N];
+  for (int i = 0; i < N; i++)
+    a[i] = 2*i + 1;
+  int *p = &a[0];
+  __builtin_printf ("%d\n", a[argc]);
+  return *(++p);
+}
+
+/* { dg-final { scan-tree-dump-times "return 3;" 1 "dom2"} } */

gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-cse-6.c

@@ -0,0 +1,20 @@
+/* Test normalization of ARRAY_REF expressions to MEM_REFs in dom.  */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-fre -fdump-tree-dom2" } */
+
+int
+main (int argc, char **argv)
+{
+  union {
+    int a[4];
+    int b[2];
+  } u;
+  u.a[0] = 1;
+  u.a[1] = 42;
+  u.a[2] = 3;
+  u.a[3] = 4;
+  __builtin_printf ("%d\n", u.a[argc]);
+  return u.b[1];
+}
+
+/* { dg-final { scan-tree-dump-times "return 42;" 1 "dom2" } } */

gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-cse-7.c

@@ -0,0 +1,21 @@
+/* Test normalization of MEM_REF expressions in dom.  */
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-tree-fre -fno-tree-pre -fdump-tree-optimized" } */
+
+typedef struct {
+  int a[8];
+} foo;
+
+foo f;
+
+int
+test ()
+{
+  foo g;
+  g.a[0] = 1; g.a[1] = 2; g.a[2] = 3; g.a[3] = 4;
+  g.a[4] = 5; g.a[5] = 6; g.a[6] = 7; g.a[7] = 8;
+  f=g;
+  return f.a[2];
+}
+
+/* { dg-final { scan-tree-dump-times "return 3;" 1 "optimized" } } */

gcc/tree-ssa-scopedtables.c

@@ -32,6 +32,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "fold-const.h"
 #include "tree-eh.h"
 #include "internal-fn.h"
+#include "tree-dfa.h"
 
 static bool hashable_expr_equal_p (const struct hashable_expr *,
 				   const struct hashable_expr *);
@@ -209,11 +210,70 @@ avail_expr_hash (class expr_hash_elt *p)
   const struct hashable_expr *expr = p->expr ();
   inchash::hash hstate;
 
+  if (expr->kind == EXPR_SINGLE)
+    {
+      /* T could potentially be a switch index or a goto dest.  */
+      tree t = expr->ops.single.rhs;
+      if (TREE_CODE (t) == MEM_REF || TREE_CODE (t) == ARRAY_REF)
+	{
+	  /* Make equivalent statements of both these kinds hash together.
+	     Dealing with both MEM_REF and ARRAY_REF allows us not to care
+	     about equivalence with other statements not considered here.  */
+	  bool reverse;
+	  HOST_WIDE_INT offset, size, max_size;
+	  tree base = get_ref_base_and_extent (t, &offset, &size, &max_size,
+					       &reverse);
+	  /* Strictly, we could try to normalize variable-sized accesses too,
+	    but here we just deal with the common case.  */
+	  if (size == max_size)
+	    {
+	      enum tree_code code = MEM_REF;
+	      hstate.add_object (code);
+	      inchash::add_expr (base, hstate);
+	      hstate.add_object (offset);
+	      hstate.add_object (size);
+	      return hstate.end ();
+	    }
+	}
+    }
+
   inchash::add_hashable_expr (expr, hstate);
 
   return hstate.end ();
 }
 
+/* Compares trees T0 and T1 to see if they are MEM_REF or ARRAY_REFs equivalent
+   to each other.  (That is, they return the value of the same bit of memory.)
+
+   Return TRUE if the two are so equivalent; FALSE if not (which could still
+   mean the two are equivalent by other means).  */
+
+static bool
+equal_mem_array_ref_p (tree t0, tree t1)
+{
+  if (TREE_CODE (t0) != MEM_REF && TREE_CODE (t0) != ARRAY_REF)
+    return false;
+  if (TREE_CODE (t1) != MEM_REF && TREE_CODE (t1) != ARRAY_REF)
+    return false;
+
+  if (!types_compatible_p (TREE_TYPE (t0), TREE_TYPE (t1)))
+    return false;
+  bool rev0;
+  HOST_WIDE_INT off0, sz0, max0;
+  tree base0 = get_ref_base_and_extent (t0, &off0, &sz0, &max0, &rev0);
+
+  bool rev1;
+  HOST_WIDE_INT off1, sz1, max1;
+  tree base1 = get_ref_base_and_extent (t1, &off1, &sz1, &max1, &rev1);
+
+  /* Types were compatible, so these are sanity checks.  */
+  gcc_assert (sz0 == sz1);
+  gcc_assert (max0 == max1);
+  gcc_assert (rev0 == rev1);
+
+  return (off0 == off1) && operand_equal_p (base0, base1, 0);
+}
+
 /* Compare two hashable_expr structures for equivalence.  They are
    considered equivalent when the expressions they denote must
    necessarily be equal.  The logic is intended to follow that of
@@ -246,9 +306,10 @@ hashable_expr_equal_p (const struct hashable_expr *expr0,
   switch (expr0->kind)
     {
     case EXPR_SINGLE:
-      return operand_equal_p (expr0->ops.single.rhs,
-                              expr1->ops.single.rhs, 0);
-
+      return equal_mem_array_ref_p (expr0->ops.single.rhs,
+				    expr1->ops.single.rhs)
+	     || operand_equal_p (expr0->ops.single.rhs,
+				 expr1->ops.single.rhs, 0);
     case EXPR_UNARY:
       if (expr0->ops.unary.op != expr1->ops.unary.op)
         return false;