'walk_stmt_load_store_addr_ops' for non-'gimple_assign_single_p (stmt)'

Richard Biener richard.guenther@gmail.com
Mon Mar 15 19:17:17 GMT 2021

On March 15, 2021 7:31:46 PM GMT+01:00, Thomas Schwinge <thomas@codesourcery.com> wrote:
>First time I'm using this API -- so the error certainly may be on my
>side.  ;-)
>What I'm doing, is a 'walk_gimple_seq', and in that one's
>'callback_stmt', call 'walk_stmt_load_store_addr_ops', to collect
>variable load/store/address-taken instances.  This did seem quite
>straight-forward, given the description; 'gcc/gimple-walk.c':
>/* For the statement STMT call the callbacks VISIT_LOAD, VISIT_STORE
>      VISIT_ADDR if non-NULL on loads, store and address-taken operands
>passing the STMT, the base of the operand, the operand itself
>  the base and DATA to it.  The base will be either a decl, an indirect
>     reference (including TARGET_MEM_REF) or the argument of an address
>       expression.
>       Returns the results of these callbacks or'ed.  */
>    bool
>    walk_stmt_load_store_addr_ops (gimple *stmt, void *data,
>                               walk_stmt_load_store_addr_fn visit_load,
>                              walk_stmt_load_store_addr_fn visit_store,
>                               walk_stmt_load_store_addr_fn visit_addr)
>    { [...] }
>Indeed, given (Fortran) 'zzz = 1', we produce GIMPLE:
>    gimple_assign <real_cst, zzz, 1.0e+0, NULL, NULL>
>..., and calling 'walk_stmt_load_store_addr_ops' on that, I see, as
>expected, the 'visit_store' callback invoked, with 'rhs' and 'arg':
>'<var_decl zzz>'.
>However, given (Fortran) 'zzz = r + r2', we produce GIMPLE:
>    gimple_assign <plus_expr, zzz, r, r2, NULL>
>..., and calling 'walk_stmt_load_store_addr_ops' on that, I see,
>unexpectedly, no callback at all invoked: neither 'visit_load', nor
>'visit_store' (nor 'visit_address', obviously).

The variables involved are registers. You only get called on memory operands. 

>From a quick look at 'gcc/gimple-walk.c:walk_stmt_load_store_addr_ops',
>this seems to intentionally be implemented in this way -- but I don't
>understand the rationale?
>Instead of 'walk_gimple_seq' -> 'callback_stmt' ->
>'walk_stmt_load_store_addr_ops', do I need to use 'walk_gimple_seq' ->
>'callback_op' -> "something"?

Yes, if you want to visit register sets and uses as a well. Note you'll also see constants that way. 


> Thomas
>Mentor Graphics (Deutschland) GmbH, Arnulfstrasse 201, 80634 München
>Registergericht München HRB 106955, Geschäftsführer: Thomas Heurung,
>Frank Thürauf

More information about the Gcc mailing list