Fix if-conversion pass for dead type-unsafe code

2014-08-08  Tom de Vries  <tom@codesourcery.com>

	PR rtl-optimization/62004
	PR rtl-optimization/62030
	* ifcvt.c (rtx_interchangeable_p): New function.
	(noce_try_move, noce_process_if_block): Use rtx_interchangeable_p.
	* emit-rtl.c (mem_attrs_eq_p): Remove static.
	* emit-rtl.h (mem_attrs_eq_p): Declare.

	* gcc.dg/pr62004.c: New test.
	* gcc.dg/pr62030.c: Same.
	* gcc.target/mips/pr62030-octeon.c: Same.

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index b5278bf..1cac518 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -263,7 +263,7 @@  mem_attrs_htab_hash (const void *x)
 
 /* Return true if the given memory attributes are equal.  */
 
-static bool
+bool
 mem_attrs_eq_p (const struct mem_attrs *p, const struct mem_attrs *q)
 {
   return (p->alias == q->alias
diff --git a/gcc/emit-rtl.h b/gcc/emit-rtl.h
index 7268090..9ccee07 100644
--- a/gcc/emit-rtl.h
+++ b/gcc/emit-rtl.h
@@ -69,6 +69,7 @@  extern void set_reg_attrs_for_parm (rtx, rtx);
 extern void set_reg_attrs_for_decl_rtl (tree t, rtx x);
 extern void adjust_reg_mode (rtx, enum machine_mode);
 extern int mem_expr_equal_p (const_tree, const_tree);
+extern bool mem_attrs_eq_p (const struct mem_attrs *, const struct mem_attrs *);
 
 extern bool need_atomic_barrier_p (enum memmodel, bool);
 
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index e3353a5..dd6df5b 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -294,6 +294,28 @@  block_fallthru (basic_block bb)
 
   return (e) ? e->dest : NULL_BLOCK;
 }
+
+/* Return true if RTXs A and B can be safely interchanged.  */
+
+static bool
+rtx_interchangeable_p (const_rtx a, const_rtx b)
+{
+  if (!rtx_equal_p (a, b))
+    return false;
+
+  if (GET_CODE (a) != MEM)
+    return true;
+
+  /* A dead type-unsafe memory reference is legal, but a live type-unsafe memory
+     reference is not.  Interchanging a dead type-unsafe memory reference with
+     a live type-safe one creates a live type-unsafe memory reference, in other
+     words, it makes the program illegal.
+     We check here conservatively whether the two memory references have equal
+     memory attributes.  */
+
+  return mem_attrs_eq_p (get_mem_attrs (a), get_mem_attrs (b));
+}
+
 
 /* Go through a bunch of insns, converting them to conditional
    execution format if possible.  Return TRUE if all of the non-note
@@ -1014,6 +1036,9 @@  noce_try_move (struct noce_if_info *if_info)
       || (rtx_equal_p (if_info->a, XEXP (cond, 1))
 	  && rtx_equal_p (if_info->b, XEXP (cond, 0))))
     {
+      if (!rtx_interchangeable_p (if_info->a, if_info->b))
+	return FALSE;
+
       y = (code == EQ) ? if_info->a : if_info->b;
 
       /* Avoid generating the move if the source is the destination.  */
@@ -2483,7 +2508,7 @@  noce_process_if_block (struct noce_if_info *if_info)
       if (! insn_b
 	  || insn_b != last_active_insn (else_bb, FALSE)
 	  || (set_b = single_set (insn_b)) == NULL_RTX
-	  || ! rtx_equal_p (x, SET_DEST (set_b)))
+	  || ! rtx_interchangeable_p (x, SET_DEST (set_b)))
 	return FALSE;
     }
   else
@@ -2496,7 +2521,7 @@  noce_process_if_block (struct noce_if_info *if_info)
 	  || BLOCK_FOR_INSN (insn_b) != BLOCK_FOR_INSN (if_info->cond_earliest)
 	  || !NONJUMP_INSN_P (insn_b)
 	  || (set_b = single_set (insn_b)) == NULL_RTX
-	  || ! rtx_equal_p (x, SET_DEST (set_b))
+	  || ! rtx_interchangeable_p (x, SET_DEST (set_b))
 	  || ! noce_operand_ok (SET_SRC (set_b))
 	  || reg_overlap_mentioned_p (x, SET_SRC (set_b))
 	  || modified_between_p (SET_SRC (set_b), insn_b, jump)
@@ -2562,7 +2587,7 @@  noce_process_if_block (struct noce_if_info *if_info)
 
   /* Look and see if A and B are really the same.  Avoid creating silly
      cmove constructs that no one will fix up later.  */
-  if (rtx_equal_p (a, b))
+  if (rtx_interchangeable_p (a, b))
     {
       /* If we have an INSN_B, we don't have to create any new rtl.  Just
 	 move the instruction that we already have.  If we don't have an
diff --git a/gcc/testsuite/gcc.dg/pr62004.c b/gcc/testsuite/gcc.dg/pr62004.c
new file mode 100644
index 0000000..c994a41
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr62004.c
@@ -0,0 +1,47 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2 -fno-tree-tail-merge" } */
+
+struct node
+{
+  struct node *next;
+  struct node *prev;
+};
+
+struct node node;
+
+struct head
+{
+  struct node *first;
+};
+
+struct head heads[5];
+
+int k = 2;
+
+struct head *head = &heads[2];
+
+int
+main ()
+{
+  struct node *p;
+
+  node.next = (void*)0;
+
+  node.prev = (void *)head;
+
+  head->first = &node;
+
+  struct node *n = head->first;
+
+  struct head *h = &heads[k];
+
+  heads[2].first = n->next;
+
+  if ((void*)n->prev == (void *)h)
+    p = h->first;
+  else
+    /* Dead tbaa-unsafe load from ((struct node *)&heads[2])->next.  */
+    p = n->prev->next;
+
+  return !(p == (void*)0);
+}
diff --git a/gcc/testsuite/gcc.dg/pr62030.c b/gcc/testsuite/gcc.dg/pr62030.c
new file mode 100644
index 0000000..b8baf93
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr62030.c
@@ -0,0 +1,50 @@ 
+/* { dg-do run } */
+/* { dg-options "-O2" } */
+
+extern void abort (void);
+
+struct node
+{
+  struct node *next;
+  struct node *prev;
+};
+
+struct node node;
+
+struct head
+{
+  struct node *first;
+};
+
+struct head heads[5];
+
+int k = 2;
+
+struct head *head = &heads[2];
+
+static int __attribute__((noinline))
+foo (void)
+{
+  node.prev = (void *)head;
+  head->first = &node;
+
+  struct node *n = head->first;
+  struct head *h = &heads[k];
+  struct node *next = n->next;
+
+  if (n->prev == (void *)h)
+    h->first = next;
+  else
+    n->prev->next = next;
+
+  n->next = h->first;
+  return n->next == &node;
+}
+
+int
+main (void)
+{
+  if (foo ())
+    abort ();
+  return 0;
+}
diff --git a/gcc/testsuite/gcc.target/mips/pr62030-octeon.c b/gcc/testsuite/gcc.target/mips/pr62030-octeon.c
new file mode 100644
index 0000000..5e3d3b3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/pr62030-octeon.c
@@ -0,0 +1,50 @@ 
+/* { dg-do run } */
+/* { dg-options "-march=octeon" } */
+
+extern void abort (void);
+
+struct node
+{
+  struct node *next;
+  struct node *prev;
+};
+
+struct node node;
+
+struct head
+{
+  struct node *first;
+};
+
+struct head heads[5];
+
+int k = 2;
+
+struct head *head = &heads[2];
+
+static int __attribute__((noinline))
+foo (void)
+{
+  node.prev = (void *)head;
+  head->first = &node;
+
+  struct node *n = head->first;
+  struct head *h = &heads[k];
+  struct node *next = n->next;
+
+  if (n->prev == (void *)h)
+    h->first = next;
+  else
+    n->prev->next = next;
+
+  n->next = h->first;
+  return n->next == &node;
+}
+
+int
+main (void)
+{
+  if (foo ())
+    abort ();
+  return 0;
+}
-- 
1.9.1