[PATCH] Do not mark address-taking stmts of volatile objects as volatile

[Richard Guenther]

During an IRC discussion I noticed that we mark p = &a[i] as volatile

  p_2 ={v} &a[i_1(D)];

in the operand scanner even though that is not necessary.  The following
patch properly guards setting the volatile flag on that we are not
processing the operands of an ADDR_EXPR currently.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2011-12-08  Richard Guenther  <rguent...@suse.de>

        * tree-ssa-operands.c (add_stmt_operand): Do not mark stmts
        volatile when processing operands of an ADDR_EXPR.
        (get_indirect_ref_operands): Likewise.
        (get_tmr_operands): Likewise.
        (get_expr_operands): Likewise.

        * gcc.dg/volatile3.c: New testcase.

Index: gcc/tree-ssa-operands.c
===================================================================
--- gcc/tree-ssa-operands.c     (revision 182107)
+++ gcc/tree-ssa-operands.c     (working copy)
@@ -668,7 +668,8 @@ add_stmt_operand (tree *var_p, gimple st
   sym = (TREE_CODE (var) == SSA_NAME ? SSA_NAME_VAR (var) : var);
 
   /* Mark statements with volatile operands.  */
-  if (TREE_THIS_VOLATILE (sym))
+  if (!(flags & opf_no_vops)
+      && TREE_THIS_VOLATILE (sym))
     gimple_set_has_volatile_ops (stmt, true);
 
   if (is_gimple_reg (sym))
@@ -728,7 +729,8 @@ get_indirect_ref_operands (gimple stmt,
 {
   tree *pptr = &TREE_OPERAND (expr, 0);
 
-  if (TREE_THIS_VOLATILE (expr))
+  if (!(flags & opf_no_vops)
+      && TREE_THIS_VOLATILE (expr))
     gimple_set_has_volatile_ops (stmt, true);
 
   /* Add the VOP.  */
@@ -747,7 +749,8 @@ get_indirect_ref_operands (gimple stmt,
 static void
 get_tmr_operands (gimple stmt, tree expr, int flags)
 {
-  if (TREE_THIS_VOLATILE (expr))
+  if (!(flags & opf_no_vops)
+      && TREE_THIS_VOLATILE (expr))
     gimple_set_has_volatile_ops (stmt, true);
 
   /* First record the real operands.  */
@@ -914,14 +917,16 @@ get_expr_operands (gimple stmt, tree *ex
     case REALPART_EXPR:
     case IMAGPART_EXPR:
       {
-       if (TREE_THIS_VOLATILE (expr))
+       if (!(flags & opf_no_vops)
+           && TREE_THIS_VOLATILE (expr))
          gimple_set_has_volatile_ops (stmt, true);
 
        get_expr_operands (stmt, &TREE_OPERAND (expr, 0), flags);
 
        if (code == COMPONENT_REF)
          {
-           if (TREE_THIS_VOLATILE (TREE_OPERAND (expr, 1)))
+           if (!(flags & opf_no_vops)
+               && TREE_THIS_VOLATILE (TREE_OPERAND (expr, 1)))
              gimple_set_has_volatile_ops (stmt, true);
            get_expr_operands (stmt, &TREE_OPERAND (expr, 2), uflags);
          }
@@ -960,7 +965,8 @@ get_expr_operands (gimple stmt, tree *ex
        /* A volatile constructor is actually TREE_CLOBBER_P, transfer
           the volatility to the statement, don't use TREE_CLOBBER_P for
           mirroring the other uses of THIS_VOLATILE in this file.  */
-       if (TREE_THIS_VOLATILE (expr))
+       if (!(flags & opf_no_vops)
+           && TREE_THIS_VOLATILE (expr))
          gimple_set_has_volatile_ops (stmt, true);
 
        for (idx = 0;
@@ -972,7 +978,8 @@ get_expr_operands (gimple stmt, tree *ex
       }
 
     case BIT_FIELD_REF:
-      if (TREE_THIS_VOLATILE (expr))
+      if (!(flags & opf_no_vops)
+         && TREE_THIS_VOLATILE (expr))
        gimple_set_has_volatile_ops (stmt, true);
       /* FALLTHRU */
 
Index: gcc/testsuite/gcc.dg/volatile3.c
===================================================================
--- gcc/testsuite/gcc.dg/volatile3.c    (revision 0)
+++ gcc/testsuite/gcc.dg/volatile3.c    (revision 0)
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-ssa" } */
+
+volatile int *q;
+void foo(int i)
+{
+  volatile int a[2];
+  volatile int *p = &a[i];
+  q = p;
+}
+
+/* { dg-final { scan-tree-dump-not "{v}" "ssa" } } */
+/* { dg-final { cleanup-tree-dump "ssa" } } */