When turning a jump to a return into a return, we need to clear EDGE_CROSSING of the fallthru edge to prevent a checking failure.

I considered not applying the transformation when the edge has EDGE_CROSSING set, but it still seems like we ought to eliminate the unnecessary jump in that case.


Bootstrapped and regression tested on x86_64.  Also did a profiled bootstrap and regression test on x86_64.


Installing on the trunk.


Jeff

commit db24bdc743cf23ea12d2dcf8254d86ab366bb46d
Author: Jeff Law <jeffreya...@gmail.com>
Date:   Tue Oct 11 00:44:26 2022 -0400

    [PR rtl-optimization/107182] Clear EDGE_CROSSING for jump->ret optimization
    
    When turning a jump to a return into a return, we need to clear 
EDGE_CROSSING
    of the fallthru edge to prevent a checking failure.
    
    I considered not applying the transformation when the edge has EDGE_CROSSING
    set, but it still seems like we ought to eliminate the unnecessary jump in
    that case.
    
    gcc/
            PR rtl-optimization/107182
            * cfgrtl.cc (fixup_reorder_chain): When optimizing a jump to a
            return, clear EDGE_CROSSING on the appropriate edge.

diff --git a/gcc/cfgrtl.cc b/gcc/cfgrtl.cc
index 281a432f6a6..f31941a61f9 100644
--- a/gcc/cfgrtl.cc
+++ b/gcc/cfgrtl.cc
@@ -4055,6 +4055,7 @@ fixup_reorder_chain (void)
          ret_label = PATTERN (ret);
          dest = EXIT_BLOCK_PTR_FOR_FN (cfun);
 
+         e_fall->flags &= ~EDGE_CROSSING;
          /* E_FALL->dest might become unreachable as a result of
             replacing the jump with a return.  So arrange to remove
             unreachable blocks.  */

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