A latent bug - use of BRANCH_EDGE on trees.

[Zdenek Dvorak]

Hello,

> I think I found a latent bug.
> 
> loopify in cfgloopmanip.c is called from tree_ssa_loop_version and
> unswitch_loop.  Of those, tree_ssa_loop_version obviously deals with
> trees in SSA form.
> 
> Now, the problem is that loopify uses BRANCH_EDGE.  While we are in
> trees, EDGE_FALLTHRU does not make sense for basic blocks ending with
> COND_EXPR.  Here is the definition of BRANCH_EDGE.
> 
> #define BRANCH_EDGE(bb)			(EDGE_SUCC ((bb), 0)->flags & EDGE_FALLTHRU \
> 					 ? EDGE_SUCC ((bb), 1) : EDGE_SUCC ((bb), 0))
> 
> Any ideas?

yes, this indeed is a problem.  There are several solutions:

1) Let the caller pass the edge corresponding to the current
   BRANCH_EDGE (switch_bb) to loopify
2) Let BRANCH_EDGE check ir_type and use EDGE_{TRUE,FALSE}_FLAG for
   trees.
3) Let EDGE_FALSE_FLAG == EDGE_FALLTHRU

I do not have any special preference here.

Zdenek