[PATCH] fix SPEC ICE - if-conversion

[Devang Patel <dpatel at apple dot com>]

Recent (in last 3-4 weeks) changes in mainline exposed one bug in  
tree if-conversion.
It causes ICE in 4 SPEC benchmarks, gcc, perlbmk, crafty and bzip2.  
While replacing
phi node with cond expr, for example

Input:
    P1 = PHI < A(3), B(4) >

Output:
    P1 = C1 ? A : B
or
    P1 = C2 ? B : A

one of the predecessor's condition is selected and it determines  
order of operands.
[ This conditions are propagated during each basic block's if- 
conversion. When one
block is if-converted, its condition is propagated into destination  
block (stored
in aux field.) ]

Now, if one of the predecessor is loop header then corresponding  
condition is
defined in latch node. This results in verify_ssa() failure, because  
definition
follows use when all loop blocks are merged into one big block. This  
patch fixes this
by adding one additional loop header check during condition selection.

2005-03-31  Devang Patel  <dpatel@apple.com>

        * tree-if-conv.c (find_phi_replacement_condition): New  
parameter, loop.
        Avoid condition from loop header.

Bootstrapped and tested on powerpc-darwin, tested on SPEC (with auto  
vectorizer ON).

OK for mainline?
Thanks,
-
Devang


Index: gcc/tree-if-conv.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/tree-if-conv.c,v
retrieving revision 2.34
diff -Idpatel.pbxuser -c -3 -p -r2.34 tree-if-conv.c
*** gcc/tree-if-conv.c  12 Mar 2005 18:35:48 -0000      2.34
--- gcc/tree-if-conv.c  31 Mar 2005 23:00:52 -0000
*************** static void add_to_predicate_list (basic
*** 117,123 ****
  static tree add_to_dst_predicate_list (struct loop * loop,  
basic_block, tree, tree,
                                       block_stmt_iterator *);
  static void clean_predicate_lists (struct loop *loop);
! static basic_block find_phi_replacement_condition (basic_block,  
tree *,
                                                    
block_stmt_iterator *);
  static void replace_phi_with_cond_modify_expr (tree, tree,  
basic_block,
                                                 block_stmt_iterator  
*);
--- 117,123 ----
  static tree add_to_dst_predicate_list (struct loop * loop,  
basic_block, tree, tree,
                                       block_stmt_iterator *);
  static void clean_predicate_lists (struct loop *loop);
! static basic_block find_phi_replacement_condition (struct loop*,  
basic_block, tree *,
                                                    
block_stmt_iterator *);
  static void replace_phi_with_cond_modify_expr (tree, tree,  
basic_block,
                                                 block_stmt_iterator  
*);
*************** clean_predicate_lists (struct loop *loop
*** 683,689 ****
     whose phi arguments are selected when cond is true.  */

  static basic_block
! find_phi_replacement_condition (basic_block bb, tree *cond,
                                  block_stmt_iterator *bsi)
  {
    edge e;
--- 683,689 ----
     whose phi arguments are selected when cond is true.  */

  static basic_block
! find_phi_replacement_condition (struct loop *loop, basic_block bb,  
tree *cond,
                                  block_stmt_iterator *bsi)
  {
    edge e;
*************** find_phi_replacement_condition (basic_bl
*** 704,721 ****
        }
      }

!   /* Use condition that is not TRUTH_NOT_EXPR in conditional modify  
expr.  */
    tmp_cond = p1->aux;
!   if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
!     {
!       *cond  = p2->aux;
!       true_bb = p2;
!     }
!   else
      {
!       *cond  = p1->aux;
!       true_bb = p1;
!     }

    /* Create temp. for the condition. Vectorizer prefers to have  
gimple
       value as condition. Various targets use different means to  
communicate
--- 704,725 ----
        }
      }

!   /* Use condition that is not TRUTH_NOT_EXPR in conditional modify  
expr.
!      However, do not use condition from loop header.  */
    tmp_cond = p1->aux;
!   if (loop->header != p1 && loop->header != p2)
      {
!       if (TREE_CODE (tmp_cond) == TRUTH_NOT_EXPR)
!       true_bb = p2;
!       else
!       true_bb = p1;
!     }
!   else if (loop->header == p1)
!     true_bb = p2;
!   else
!     true_bb = p1;
!
!   *cond = true_bb->aux;

    /* Create temp. for the condition. Vectorizer prefers to have  
gimple
       value as condition. Various targets use different means to  
communicate
*************** process_phi_nodes (struct loop *loop)
*** 834,840 ****
        /* BB has two predecessors. Using predecessor's aux field, set
         appropriate condition for the PHI node replacement.  */
        if (phi)
!       true_bb = find_phi_replacement_condition (bb, &cond, &bsi);

        while (phi)
        {
--- 838,844 ----
        /* BB has two predecessors. Using predecessor's aux field, set
         appropriate condition for the PHI node replacement.  */
        if (phi)
!       true_bb = find_phi_replacement_condition (loop, bb, &cond,  
&bsi);

        while (phi)
        {