C++ PATCH to while/loop conditions

[Jason Merrill <jason at redhat dot com>]

This patch completes moving SCOPE_STMTs out of conditions in C++ statements
by moving evaluation of complex loop conditions into the loop body.  This
is basically the same transformation as is done by maybe_fixup_loop_cond in
the tree-ssa branch, but done at build time instead.

I believe this does away with the only reason for C/C++ scopes to be
represented by begin/end pairs rather than containers, though I haven't
actually checked yet.

Tested i686-pc-linux-gnu, applied to trunk.

2002-08-15  Jason Merrill  <jason@redhat.com>

	* semantics.c (finish_then_clause): Remove redundant assignment.
	(finish_if_stmt, begin_switch_stmt, finish_switch_stmt): Move the
	extra binding level outside the if/switch statement.
	(finish_while_cond, finish_for_cond): Rewrite complex condition
	into the loop body.

*** semantics.c.~1~	Mon Aug 12 19:48:30 2002
--- semantics.c	Fri Aug 16 10:40:09 2002
*************** finish_then_clause (if_stmt)
*** 266,272 ****
       tree if_stmt;
  {
    RECHAIN_STMTS (if_stmt, THEN_CLAUSE (if_stmt));
-   last_tree = if_stmt;
    return if_stmt;
  }
  
--- 266,271 ----
*************** finish_else_clause (if_stmt)
*** 292,312 ****
  void 
  finish_if_stmt ()
  {
-   do_poplevel ();
    finish_stmt ();
! }
! 
! void
! clear_out_block ()
! {
!   /* If COND wasn't a declaration, clear out the
!      block we made for it and start a new one here so the
!      optimization in expand_end_loop will work.  */
!   if (getdecls () == NULL_TREE)
!     {
!       do_poplevel ();
!       do_pushlevel ();
!     }
  }
  
  /* Begin a while-statement.  Returns a newly created WHILE_STMT if
--- 291,298 ----
  void 
  finish_if_stmt ()
  {
    finish_stmt ();
!   do_poplevel ();
  }
  
  /* Begin a while-statement.  Returns a newly created WHILE_STMT if
*************** finish_while_stmt_cond (cond, while_stmt
*** 331,338 ****
       tree while_stmt;
  {
    cond = maybe_convert_cond (cond);
!   FINISH_COND (cond, while_stmt, WHILE_COND (while_stmt));
!   clear_out_block ();
  }
  
  /* Finish a while-statement, which may be given by WHILE_STMT.  */
--- 317,342 ----
       tree while_stmt;
  {
    cond = maybe_convert_cond (cond);
!   if (getdecls () == NULL_TREE)
!     /* It was a simple condition; install it.  */
!     WHILE_COND (while_stmt) = cond;
!   else
!     {
!       /* If there was a declaration in the condition, we can't leave it
! 	 there; transform
! 	    while (A x = 42) { }
! 	 to
! 	    while (true) { A x = 42; if (!x) break; }  */
!       tree if_stmt;
!       WHILE_COND (while_stmt) = boolean_true_node;
! 
!       if_stmt = begin_if_stmt ();
!       cond = build_unary_op (TRUTH_NOT_EXPR, cond, 0);
!       finish_if_stmt_cond (cond, if_stmt);
!       finish_break_stmt ();
!       finish_then_clause (if_stmt);
!       finish_if_stmt ();
!     }
  }
  
  /* Finish a while-statement, which may be given by WHILE_STMT.  */
*************** finish_for_cond (cond, for_stmt)
*** 448,455 ****
       tree for_stmt;
  {
    cond = maybe_convert_cond (cond);
!   FINISH_COND (cond, for_stmt, FOR_COND (for_stmt));
!   clear_out_block ();
  }
  
  /* Finish the increment-EXPRESSION in a for-statement, which may be
--- 452,477 ----
       tree for_stmt;
  {
    cond = maybe_convert_cond (cond);
!   if (getdecls () == NULL_TREE)
!     /* It was a simple condition; install it.  */
!     FOR_COND (for_stmt) = cond;
!   else
!     {
!       /* If there was a declaration in the condition, we can't leave it
! 	 there; transform
! 	    for (; A x = 42;) { }
! 	 to
! 	    for (;;) { A x = 42; if (!x) break; }  */
!       tree if_stmt;
!       FOR_COND (for_stmt) = NULL_TREE;
! 
!       if_stmt = begin_if_stmt ();
!       cond = build_unary_op (TRUTH_NOT_EXPR, cond, 0);
!       finish_if_stmt_cond (cond, if_stmt);
!       finish_break_stmt ();
!       finish_then_clause (if_stmt);
!       finish_if_stmt ();
!     }
  }
  
  /* Finish the increment-EXPRESSION in a for-statement, which may be
*************** tree
*** 502,510 ****
  begin_switch_stmt ()
  {
    tree r;
    r = build_stmt (SWITCH_STMT, NULL_TREE, NULL_TREE, NULL_TREE);
    add_stmt (r);
-   do_pushlevel ();
    return r;
  }
  
--- 524,532 ----
  begin_switch_stmt ()
  {
    tree r;
+   do_pushlevel ();
    r = build_stmt (SWITCH_STMT, NULL_TREE, NULL_TREE, NULL_TREE);
    add_stmt (r);
    return r;
  }
  
*************** finish_switch_stmt (switch_stmt)
*** 560,567 ****
  {
    RECHAIN_STMTS (switch_stmt, SWITCH_BODY (switch_stmt));
    pop_switch (); 
-   do_poplevel ();
    finish_stmt ();
  }
  
  /* Generate the RTL for T, which is a TRY_BLOCK. */
--- 582,589 ----
  {
    RECHAIN_STMTS (switch_stmt, SWITCH_BODY (switch_stmt));
    pop_switch (); 
    finish_stmt ();
+   do_poplevel ();
  }
  
  /* Generate the RTL for T, which is a TRY_BLOCK. */