[gcc r16-5453] ipa: Add early return when the hashed edge is a callback-carrying edge.

[Josef Melcr]

https://gcc.gnu.org/g:5527996c4431821c10be39e89b8b2caaa93e5efe

commit r16-5453-g5527996c4431821c10be39e89b8b2caaa93e5efe
Author: Josef Melcr <josef.melcr@suse.com>
Date:   Thu Nov 20 13:32:45 2025 +0100

    ipa: Add early return when the hashed edge is a callback-carrying edge.
    
    The inclusion of this early return statement has been discussed before,
    it was ultimately left out of the original patch, but it turns out to be
    necessary.
    
    When a callback edge is being created, it is first created by
    symbol_table::create_edge, which is where it is added to the call site
    hash.  However, its callback flag is not set at that point, so the early
    return for callback edges doesn't affect it.  This causes the wrong edge
    to be hashed, ultimately leading to segfaults and ICEs. This happens
    many times in the testsuite, the one I noticed first was
    libgomp.fortran/simd7.f90.
    
    gcc/ChangeLog:
    
            PR ipa/122358
            * cgraph.cc (cgraph_add_edge_to_call_site_hash): Add an early
            return when the hashed edge is a callback-carrying edge.
    
    Signed-off-by: Josef Melcr <josef.melcr@suse.com>

Diff:
---
 gcc/cgraph.cc | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/gcc/cgraph.cc b/gcc/cgraph.cc
index ab09376a1a0d..3c21e1749430 100644
--- a/gcc/cgraph.cc
+++ b/gcc/cgraph.cc
@@ -885,9 +885,10 @@ cgraph_add_edge_to_call_site_hash (cgraph_edge *e)
       gcc_assert (edge->speculative || edge->has_callback);
       if (edge->has_callback)
 	/* If the slot is already occupied, then the hashed edge is the
-	   callback-carrying edge, which is desired behavior, so we can safely
-	   return.  */
-	gcc_checking_assert (edge == e);
+	   callback-carrying edge, which is desired behavior.  In some cases,
+	   the callback flag of E is not set yet and so the early exit above is
+	   not taken.  */
+	return;
       if (e->callee && (!e->prev_callee
 			|| !e->prev_callee->speculative
 			|| e->prev_callee->call_stmt != e->call_stmt))