[Bug tree-optimization/113134] gcc does not version loops with early break conditions that don't have side-effects

[juzhe.zhong at rivai dot ai via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113134

--- Comment #19 from JuzheZhong <juzhe.zhong at rivai dot ai> ---

The loop is:

bb 3 -> bb 4 -> bb 5
  |       |______⬆
  |______________⬆

The condition in bb 3 is if (i_21 == 1001).
The condition in bb 4 is if (N_13(D) > i_18).

Look into lsplit:
This loop doesn't satisfy the check of:
if (split_loop (loop) || split_loop_on_cond (loop))

In split_loop_on_cond, it's trying to split the loop that condition
is loop invariant.  However, no matter bb 3 or bb 4, their conditions
are not loop invariant.

I wonder whether we should add a new kind of loop splitter like:

diff --git a/gcc/tree-ssa-loop-split.cc b/gcc/tree-ssa-loop-split.cc
index 04215fe7937..a4081b9b6f5 100644
--- a/gcc/tree-ssa-loop-split.cc
+++ b/gcc/tree-ssa-loop-split.cc
@@ -1769,7 +1769,8 @@ tree_ssa_split_loops (void)
       if (optimize_loop_for_size_p (loop))
        continue;

-      if (split_loop (loop) || split_loop_on_cond (loop))
+      if (split_loop (loop) || split_loop_on_cond (loop)
+         || split_loop_for_early_break (loop))
        {
          /* Mark our containing loop as having had some split inner loops.  */
          loop_outer (loop)->aux = loop;