[gcc r12-5843] bpf: avoid potential NULL pointer dereference

[David Faust]

https://gcc.gnu.org/g:e4c2b55b4cefc574a4c2b0b06928220edb9b3f2c

commit r12-5843-ge4c2b55b4cefc574a4c2b0b06928220edb9b3f2c
Author: David Faust <david.faust@oracle.com>
Date:   Tue Dec 7 11:45:48 2021 -0800

    bpf: avoid potential NULL pointer dereference
    
    If the result from SSA_NAME_DEF_STMT is NULL, we could try to
    dereference it anyway and ICE. Avoid this.
    
    gcc/ChangeLog:
    
            * config/bpf/bpf.c (handle_attr_preserve): Avoid calling
            is_gimple_assign with a NULL pointer.

Diff:
---
 gcc/config/bpf/bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/config/bpf/bpf.c b/gcc/config/bpf/bpf.c
index 9d2c0bb6818..c054c1ead6b 100644
--- a/gcc/config/bpf/bpf.c
+++ b/gcc/config/bpf/bpf.c
@@ -1482,7 +1482,7 @@ handle_attr_preserve (function *fn)
 		      && TREE_CODE (TREE_OPERAND (expr, 0)) == SSA_NAME)
 		    {
 		      gimple *def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (expr, 0));
-		      if (is_gimple_assign (def_stmt))
+		      if (def_stmt && is_gimple_assign (def_stmt))
 			expr = gimple_assign_rhs1 (def_stmt);
 		    }