Hi Everyone, I am new to GIMPLE, and have a question about GIMPLE_PHI node. If I add "-fdump-tree-ssa-raw" option, the output file contains every GIMPLE_PHI node. However, when I added a new pass before pass "pass_ipa_lto_gimple_out", and traversed each statement using the following piece of codes: FOR_EACH_BB (bb){ for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)){ stmt = gsi_stmt (gsi); .... No GIMPLE_PHI node is encountered, but the SSA_NAME defined in the missed GIMPLE_PHI node are still used in other statements. Take the following debugging info as an example. SSA_NAME 0x7ffff7fc1680 is used in stmt_cur, but "a_1 = PHI <a_5(3), a_7(4)>" is not encountered when traversing each gimple statement. (gdb) p debug_tree(gimple_assign_rh2(stmt_cur)) <ssa_name 0x7fff7c1680 (skipping some info) visited var <var_decl 0x7fff700a790 a>def_stmt a_1=PHI <a_5(3), a_7(4)> version 1> Did I do something wrong? Where are those GIMPLE_PHI nodes? Thanks a lot for your help! Beicy