On March 15, 2021 7:31:46 PM GMT+01:00, Thomas Schwinge
<tho...@codesourcery.com> wrote:
>Hi!
>
>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
>and
> VISIT_ADDR if non-NULL on loads, store and address-taken operands
>passing the STMT, the base of the operand, the operand itself
>containing
> 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.
Richard.
>
>Grüße
> Thomas
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