I have been fighting with a simple problem for the past few nights. In my GIMPLE pass I create a variable, an ssa name for that variable, and then assign it to the LHS of a call I build:
call = gimple_build_call(fndecl, 0); decl = create_tmp_var(TREE_TYPE(TREE_TYPE(test_decode_fndecl)), "FOO"); ssa = make_ssa_name(decl, call); gimple_set_lhs(call, ssa); gsi_insert_before(&gsi, call, GSI_SAME_STMT); I verify the GIMPLE and it looks proper: char * FOO.2; /* some gimple code */ FOO.2_8 = fn(); strcat(&mylocal, FOO.2_8); However, when I build with -Os the GIMPLE looks like: char * FOO.2; /* some gimple code */ fn(); strcat(&mylocal, FOO.2_8); And the compiler segfaults in "ptr_deref_may_alias_decl_p" for 'ptr' FOO.2_8 and 'decl' mylocal arguments. The segfault occurs because TREE_TYPE(ptr) is NULL and calling POINTER_TYPE_P(TREE_TYPE(ptr)) dereferences a NULL. After more debugging, it is eliminate_unnecessary_stmts() which tries to remove the 'FOO.2_8 = fn();' statement. In that routine, the LHS is considered "dead" and because of that the routine sets the LHS to NULL. So, I guess my question is, how can I force this stmt to hang around? I looked at eliminate_unnecessary_stmts, and do not see any specific flags I can set to the stmt to make 'em hang around, and I do not know what to do to make LHS appear not "dead." Even if I set 'ssa' TREE_USED and 'decl' as DECL_PRESERVE_P. Thanks for any information! -Matt
