[committed] [PR rtl-optimization/107182] Clear EDGE_CROSSING for jump->ret optimization

[Jeff Law <jeffreyalaw@gmail.com>]

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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


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commit db24bdc743cf23ea12d2dcf8254d86ab366bb46d
Author: Jeff Law <jeffreyalaw@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.  */