[Bug optimization/11373] [tree-ssa] asm generated lhs expressions are discarded

["dnovillo at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11373



------- Additional Comments From dnovillo at redhat dot com  2003-07-25 23:51 -------
Subject: Re:  [tree-ssa] asm generated lhs
	expressions are discarded


This patch should fix the problem.  I will commit it in my next round of
patches.


Diego.

	PR optimization/11373
	* tree-ssa-dce.c (stmt_useful_p): Scan operands before checking
	for volatile operands.
	* tree-dfa.c (get_expr_operands): If a nonzero constant is used in
	an INDIRECT_REF expression, mark the statement as having volatile
	operands.
	(may_access_global_mem_p): Return true if the pointer is a nonzero
	constant.

Index: tree-ssa-dce.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-ssa-dce.c,v
retrieving revision 1.1.2.47
diff -d -u -p -r1.1.2.47 tree-ssa-dce.c
--- tree-ssa-dce.c	22 Jul 2003 02:50:15 -0000	1.1.2.47
+++ tree-ssa-dce.c	25 Jul 2003 23:48:44 -0000
@@ -283,12 +283,12 @@ stmt_useful_p (tree stmt)
 	    return true;
     }
 
+  /* Examine all the stores in this statement.  */
+  get_stmt_operands (stmt);
+
   /* If the statement has volatile operands, it needs to be preserved.  */
   if (stmt_ann (stmt)->has_volatile_ops)
     return true;
-
-  /* Examine all the stores in this statement.  */
-  get_stmt_operands (stmt);
 
   ops = def_ops (stmt);
   for (i = 0; ops && i < VARRAY_ACTIVE_SIZE (ops); i++)
Index: tree-dfa.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-dfa.c,v
retrieving revision 1.1.4.135
diff -d -u -p -r1.1.4.135 tree-dfa.c
--- tree-dfa.c	25 Jul 2003 03:13:07 -0000	1.1.4.135
+++ tree-dfa.c	25 Jul 2003 23:48:44 -0000
@@ -377,6 +377,15 @@ get_expr_operands (tree stmt, tree *expr
 	  add_stmt_operand (&TREE_OPERAND (ptr, 0), stmt, flags, prev_vops);
 	  return;
 	}
+      else if (TREE_CONSTANT (ptr) && !integer_zerop (ptr))
+	{
+	  /* If a constant is used as a pointer, we can't generate a real
+	     operand for it but we mark the statement volatile to prevent
+	     optimizations from messing things up.  */
+	  stmt_ann (stmt)->has_volatile_ops = true;
+	  return;
+	}
+
 
       /* Add a USE operand for the base pointer.  */
       get_expr_operands (stmt, &TREE_OPERAND (expr, 0), opf_none, prev_vops);
@@ -2103,6 +2112,10 @@ may_access_global_mem_p (tree expr)
 
   /* Call expressions that return pointers may point to global memory.  */
   if (TREE_CODE (expr) == CALL_EXPR)
+    return true;
+
+  /* A non-NULL constant used as a pointer points to global memory.  */
+  if (TREE_CONSTANT (expr) && !integer_zerop (expr))
     return true;
 
   /* Recursively check the expression's operands.  */