re PR rtl-optimization/85180 (Infinite loop in RTL DSE optimizer)

2018-04-06  Richard Biener  <rguenther@suse.de>

	PR middle-end/85180
	* alias.c (find_base_term): New wrapper around find_base_term
	unwinding CSELIB_VAL_PTR changes.
	(find_base_term): Do not restore CSELIB_VAL_PTR during the
	recursion.

	* gcc.dg/pr85180.c: New testcase.

From-SVN: r259166

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f96b375cc4240d03224b061775e0d38484962fc4..76771a28364dd7450fa70438fa07823b1b0fe9d6 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2018-04-06  Richard Biener  <rguenther@suse.de>
+
+       PR middle-end/85180
+       * alias.c (find_base_term): New wrapper around find_base_term
+       unwinding CSELIB_VAL_PTR changes.
+       (find_base_term): Do not restore CSELIB_VAL_PTR during the
+       recursion.
+
 2018-04-06  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>
 
        * config/s390/s390.c (s390_z10_optimize_cmp): Expand dedicated NOP

diff --git a/gcc/alias.c b/gcc/alias.c
index eac36a515191519001881db42f6649a2294548f1..74032f8503b75eaf4c9039d699764e5894f8cd74 100644 (file)
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -1876,7 +1876,8 @@ rtx_equal_for_memref_p (const_rtx x, const_rtx y)
 }
 
 static rtx
-find_base_term (rtx x)
+find_base_term (rtx x, vec<std::pair<cselib_val *,
+                                    struct elt_loc_list *> > &visited_vals)
 {
   cselib_val *val;
   struct elt_loc_list *l, *f;
@@ -1910,7 +1911,7 @@ find_base_term (rtx x)
     case POST_DEC:
     case PRE_MODIFY:
     case POST_MODIFY:
-      return find_base_term (XEXP (x, 0));
+      return find_base_term (XEXP (x, 0), visited_vals);
 
     case ZERO_EXTEND:
     case SIGN_EXTEND:  /* Used for Alpha/NT pointers */
@@ -1921,7 +1922,7 @@ find_base_term (rtx x)
        return 0;
 
       {
-       rtx temp = find_base_term (XEXP (x, 0));
+       rtx temp = find_base_term (XEXP (x, 0), visited_vals);
 
        if (temp != 0 && CONSTANT_P (temp))
          temp = convert_memory_address (Pmode, temp);
@@ -1940,7 +1941,9 @@ find_base_term (rtx x)
        return static_reg_base_value[STACK_POINTER_REGNUM];
 
       f = val->locs;
-      /* Temporarily reset val->locs to avoid infinite recursion.  */
+      /* Reset val->locs to avoid infinite recursion.  */
+      if (f)
+       visited_vals.safe_push (std::make_pair (val, f));
       val->locs = NULL;
 
       for (l = f; l; l = l->next)
@@ -1949,16 +1952,15 @@ find_base_term (rtx x)
            && !CSELIB_VAL_PTR (l->loc)->locs->next
            && CSELIB_VAL_PTR (l->loc)->locs->loc == x)
          continue;
-       else if ((ret = find_base_term (l->loc)) != 0)
+       else if ((ret = find_base_term (l->loc, visited_vals)) != 0)
          break;
 
-      val->locs = f;
       return ret;
 
     case LO_SUM:
       /* The standard form is (lo_sum reg sym) so look only at the
          second operand.  */
-      return find_base_term (XEXP (x, 1));
+      return find_base_term (XEXP (x, 1), visited_vals);
 
     case CONST:
       x = XEXP (x, 0);
@@ -1984,7 +1986,7 @@ find_base_term (rtx x)
           other operand is the base register.  */
 
        if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
-         return find_base_term (tmp2);
+         return find_base_term (tmp2, visited_vals);
 
        /* If either operand is known to be a pointer, then prefer it
           to determine the base term.  */
@@ -2001,12 +2003,12 @@ find_base_term (rtx x)
           term is from a pointer or is a named object or a special address
           (like an argument or stack reference), then use it for the
           base term.  */
-       rtx base = find_base_term (tmp1);
+       rtx base = find_base_term (tmp1, visited_vals);
        if (base != NULL_RTX
            && ((REG_P (tmp1) && REG_POINTER (tmp1))
                 || known_base_value_p (base)))
          return base;
-       base = find_base_term (tmp2);
+       base = find_base_term (tmp2, visited_vals);
        if (base != NULL_RTX
            && ((REG_P (tmp2) && REG_POINTER (tmp2))
                 || known_base_value_p (base)))
@@ -2020,7 +2022,7 @@ find_base_term (rtx x)
 
     case AND:
       if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0)
-       return find_base_term (XEXP (x, 0));
+       return find_base_term (XEXP (x, 0), visited_vals);
       return 0;
 
     case SYMBOL_REF:
@@ -2032,6 +2034,19 @@ find_base_term (rtx x)
     }
 }
 
+/* Wrapper around the worker above which removes locs from visited VALUEs
+   to avoid visiting them multiple times.  We unwind that changes here.  */
+
+static rtx
+find_base_term (rtx x)
+{
+  auto_vec<std::pair<cselib_val *, struct elt_loc_list *>, 32> visited_vals;
+  rtx res = find_base_term (x, visited_vals);
+  for (unsigned i = 0; i < visited_vals.length (); ++i)
+    visited_vals[i].first->locs = visited_vals[i].second;
+  return res;
+}
+
 /* Return true if accesses to address X may alias accesses based
    on the stack pointer.  */
 

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cafaae9940868d5ee58c73245f4976c6002f28ba..f63977ba8d4e88479c1619b73339371e1c5a38a2 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2018-04-06  Richard Biener  <rguenther@suse.de>
+
+       PR middle-end/85180
+       * gcc.dg/pr85180.c: New testcase.
+
 2018-04-06  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>
 
        * gcc.target/s390/vector/vcond-shift.c: Use the proper conditions

diff --git a/gcc/testsuite/gcc.dg/pr85180.c b/gcc/testsuite/gcc.dg/pr85180.c
new file mode 100644 (file)
index 0000000..07c77fb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr85180.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+char *bar (void);
+__INTPTR_TYPE__ baz (void);
+
+void
+foo (__INTPTR_TYPE__ *q)
+{
+  char *p = bar ();
+  __INTPTR_TYPE__ a = baz ();
+  __INTPTR_TYPE__ b = baz ();
+  int i = 0;
+#define X q[i++] = a; q[i++] = b; a = a + b; b = b + a;
+#define Y X X X X X X X X X X
+#define Z Y Y Y Y Y Y Y Y Y Y
+  Z Z Z Z Z Z Z Z Z Z
+      p[a] = 1;
+  p[b] = 2;
+}