re PR c++/25979 (incorrect codegen for conditional [SVO issue])

PR c++/25979
        * gimplify.c (gimplify_modify_expr_rhs): Disable *& optimization for now.

        PR middle-end/25977
        * gimplify.c (gimplify_modify_expr_rhs): It's not always safe to do RVO
        on the return slot if it's an NRV.

From-SVN: r110565

gcc/ChangeLog

@@ -1,3 +1,12 @@
+2006-02-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/25979
+	* gimplify.c (gimplify_modify_expr_rhs): Disable *& optimization for now.
+
+	PR middle-end/25977
+	* gimplify.c (gimplify_modify_expr_rhs): It's not always safe to do RVO
+	on the return slot if it's an NRV.
+
 2006-02-03  Zdenek Dvorak <dvorakz@suse.cz>
 
 	* tree-ssa-loop-ivopts.c (enum use_type): Remove USE_OUTER.

gcc/gimplify.c

@@ -3190,6 +3190,7 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
   while (ret != GS_UNHANDLED)
     switch (TREE_CODE (*from_p))
       {
+#if 0
       case INDIRECT_REF:
 	{
 	  /* If we have code like 
@@ -3211,6 +3212,7 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
 	    ret = GS_UNHANDLED;
 	  break;
 	}
+#endif
 
       case TARGET_EXPR:
 	{
@@ -3272,8 +3274,9 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
 	    bool use_target;
 
 	    if (TREE_CODE (*to_p) == RESULT_DECL
+		&& DECL_NAME (*to_p) == NULL_TREE
 		&& needs_to_live_in_memory (*to_p))
-	      /* It's always OK to use the return slot directly.  */
+	      /* It's OK to use the return slot directly unless it's an NRV. */
 	      use_target = true;
 	    else if (!is_gimple_non_addressable (*to_p))
 	      /* Don't use the original target if it's already addressable;

gcc/testsuite/g++.dg/opt/nrv10.C

@@ -0,0 +1,48 @@
+// PR c++/25979
+// Bug: we were eliding too many temporaries, so that a1 was used
+// as both 'a' and 'x' in the second operator+.
+// { dg-do run }
+
+struct A
+{
+    A() : data1_(0), data2_(0) {}
+    A(int i, int j) : data1_(i), data2_(j) {}
+    A operator+(int);
+    friend A operator+(int, const A&);
+    ~A() {}
+//private:
+    int data1_;
+    int data2_;
+};
+
+extern bool x;
+
+extern "C" void abort ();
+
+int main()
+{
+    A a1(1,2);
+    a1 = (x ? a1 + 3 : 3 + a1);
+    if (a1.data1_ != 3 || a1.data2_ != 2)
+      abort ();
+}
+
+bool x = false;
+
+A
+A::operator+(int i)
+{
+    A a;
+    a = *this;
+    a.data2_ = i;
+    return a;
+}
+
+A
+operator+(int i, const A& x)
+{
+    A a;
+    a = x;
+    a.data1_ = i;
+    return a;
+}

gcc/testsuite/g++.dg/opt/nrv11.C

@@ -0,0 +1,58 @@
+// PR middle-end/25977
+// Bug: We were assuming that the return slot of the current function is
+// always safe to use as the return slot for another call, because its
+// address cannot escape.  But its address can escape if we perform the
+// named return value optimization.
+
+// { dg-do run }
+
+struct A
+{
+    A( int left, int top, int width, int height )
+      : x1(left), y1(top), x2(left+width-1), y2(top+height-1) {}
+
+    //A(const A& o) : x1(o.x1), y1(o.y1), x2(o.x2), y2(o.y2) {}
+    //A& operator=(const A& o ) { x1=o.x1; y1=o.y1; x2=o.x2; y2=o.y2; return *this; }
+
+    A  operator&(const A &r) const
+    {
+	A tmp(0, 0, -1, -1);
+	tmp.x1 = ((r.x1) < (x1) ? (x1) : (r.x1));
+	tmp.x2 = ((x2) < (r.x2) ? (x2) : (r.x2));
+	tmp.y1 = ((r.y1) < (y1) ? (y1) : (r.y1));
+	tmp.y2 = ((y2) < (r.y2) ? (y2) : (r.y2));
+	return tmp;
+    }
+
+    int x1;
+    int y1;
+    int x2;
+    int y2;
+};
+
+bool operator==( const A &r1, const A &r2 )
+{
+    return r1.x1==r2.x1 && r1.x2==r2.x2 && r1.y1==r2.y1 && r1.y2==r2.y2;
+}
+
+static A test()
+{
+    A all = A( 0, 0, 1024, 768);
+    A a = all;
+    A r = all;
+    a = a & r;
+    return a;
+}
+
+extern "C" void abort(void);
+
+int main( int argc, char ** argv )
+{
+    A all = A( 0, 0, 1024, 768);
+    A a = test();
+
+    if ( ! ( a == all))
+      abort();
+
+    return 0;
+}

gcc/testsuite/g++.dg/opt/temp1.C

@@ -1,6 +1,6 @@
 // PR c++/16405
 // { dg-options "-O2" } 
-// { dg-do run }
+// { dg-do run { xfail *-*-* } }
 
 // There should be exactly one temporary generated for the code in "f"
 // below when optimizing -- for the result of "b + c".  We have no