[PATCH] Fix simplify-rtx endless recursion (PR debug/64511)

[Jakub Jelinek]

Hi!

This patch fixes endless recursion, when we have e.g.
(eq (and (mem (mem)) (const_int 0)) (const_int 0))
and one of the MEMs is volatile (side_effects_p is true for it).
Due to the side effects, (and ... (const_int 0)) is not folded into 0,
and these two hunks then attempt to "simplify" it as
(eq (and (not (mem (mem))) (const_int 0)) (const_int 0))
and recurse that way until running out of stack.
The patch disables it for const0_rtx, because in that case it is never
an optimization.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2015-01-21  Jakub Jelinek  <ja...@redhat.com>

        PR debug/64511
        * simplify-rtx.c (simplify_relational_operation_1): Don't try to
        optimize (eq/ne (and (side_effects) (const_int 0)) (const_int 0))
        into (eq/ne (and (not (side_effects)) (const_int 0)) (const_int 0)).

        * gcc.dg/pr64511.c: New test.

--- gcc/simplify-rtx.c.jj       2015-01-19 09:31:25.000000000 +0100
+++ gcc/simplify-rtx.c  2015-01-21 11:31:28.210575916 +0100
@@ -4589,7 +4589,8 @@ simplify_relational_operation_1 (enum rt
   if ((code == EQ || code == NE)
       && op0code == AND
       && rtx_equal_p (XEXP (op0, 0), op1)
-      && !side_effects_p (op1))
+      && !side_effects_p (op1)
+      && op1 != CONST0_RTX (cmp_mode))
     {
       rtx not_y = simplify_gen_unary (NOT, cmp_mode, XEXP (op0, 1), cmp_mode);
       rtx lhs = simplify_gen_binary (AND, cmp_mode, not_y, XEXP (op0, 0));
@@ -4602,7 +4603,8 @@ simplify_relational_operation_1 (enum rt
   if ((code == EQ || code == NE)
       && op0code == AND
       && rtx_equal_p (XEXP (op0, 1), op1)
-      && !side_effects_p (op1))
+      && !side_effects_p (op1)
+      && op1 != CONST0_RTX (cmp_mode))
     {
       rtx not_x = simplify_gen_unary (NOT, cmp_mode, XEXP (op0, 0), cmp_mode);
       rtx lhs = simplify_gen_binary (AND, cmp_mode, not_x, XEXP (op0, 1));
--- gcc/testsuite/gcc.dg/pr64511.c.jj   2015-01-21 11:36:54.527916771 +0100
+++ gcc/testsuite/gcc.dg/pr64511.c      2015-01-21 11:37:14.388572338 +0100
@@ -0,0 +1,23 @@
+/* PR debug/64511 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -g" } */
+
+int a, c;
+int *volatile b;
+
+void
+foo (int p)
+{
+  int d;
+  int *e = &a;
+  d = ((p == 0) & *e) != 0;
+  b = e;
+  for (; c;)
+    ;
+}
+
+void
+bar (void)
+{
+  foo (1);
+}

        Jakub