Richard Biener <richard.guent...@gmail.com> writes:
> On Tue, Jul 25, 2017 at 7:45 PM, Marc Glisse <marc.gli...@inria.fr> wrote:
>> On Tue, 25 Jul 2017, Richard Biener wrote:
>>
>>>> I think we need Richard to say what the intent is for the valueization
>>>> function. It is used both to stop looking at defining stmt if the return
>>>> is
>>>> NULL, and to replace/optimize one SSA_NAME with another, but currently it
>>>> seems hard to prevent looking at the defining statement without
>>>> preventing
>>>> from looking at the SSA_NAME at all.
>>>
>>>
>>> Yeah, this semantic overloading is an issue. For gimple_build we have
>>> nothing
>>> to "valueize" but we only use it to tell genmatch that it may not look at
>>> the
>>> SSA_NAME_DEF_STMT.
>>>
>>>> I guess we'll need a fix in genmatch...
>>>
>>>
>>> I'll have a look tomorrow.
>>
>>
>> My impression yesterday was that we could replace the current do_valueize
>> wrapper by 2 wrappers (without touching the valueize callbacks):
>> - may_check_def_stmt, which returns a bool corresponding to the current
>> do_valueize != NULL_TREE
>> - maybe_valueize, which tries to valueize, but if it gets a NULL_TREE, it
>> returns its argument unchanged.
>>
>> Not very confident about it though.
>
> Note I've been there in the past (twice I think) but always ran into existing
> latent issues. So hopefully we've resolved those, I'm testing the following
> simplified variant of what I had back in time.
>
> It'll produce
>
> switch (TREE_CODE (op0))
> {
> case SSA_NAME:
> if (gimple *def_stmt = get_def (valueize, op0))
> {
> if (gassign *def = dyn_cast <gassign *> (def_stmt))
> switch (gimple_assign_rhs_code (def))
> {
> case MINUS_EXPR:
> {
> tree o20 = gimple_assign_rhs1 (def);
> o20 = do_valueize (valueize, o20);
> tree o21 = gimple_assign_rhs2 (def);
> o21 = do_valueize (valueize, o21);
> if (op1 == o21 || (operand_equal_p (op1, o21, 0) &&
> types_match (op1, o21)))
> {
>
> which also indents less which is nice.
>
> Bootstrap/regtest running on x86_64-unknown-linux-gnu.
>
> Richard.
>
> 2017-07-26 Richard Biener <rguent...@suse.de>
>
> * gimple-match-head.c (do_valueize): Return OP if valueize
> returns NULL_TREE.
> (get_def): New helper to get at the def stmt of a SSA name
> if valueize allows.
> * genmatch.c (dt_node::gen_kids_1): Use get_def instead of
> do_valueize to get at the def stmt.
> (dt_operand::gen_gimple_expr): Simplify do_valueize calls.
>
>
>> --
>> Marc Glisse
>
> 2017-07-26 Richard Biener <rguent...@suse.de>
>
> * gimple-match-head.c (do_valueize): Return OP if valueize
> returns NULL_TREE.
> (get_def): New helper to get at the def stmt of a SSA name
> if valueize allows.
> * genmatch.c (dt_node::gen_kids_1): Use get_def instead of
> do_valueize to get at the def stmt.
> (dt_operand::gen_gimple_expr): Simplify do_valueize calls.
>
> Index: gcc/gimple-match-head.c
> ===================================================================
> --- gcc/gimple-match-head.c (revision 250518)
> +++ gcc/gimple-match-head.c (working copy)
> @@ -779,10 +779,25 @@ inline tree
> do_valueize (tree (*valueize)(tree), tree op)
> {
> if (valueize && TREE_CODE (op) == SSA_NAME)
> - return valueize (op);
> + {
> + tree tem = valueize (op);
> + if (tem)
> + return tem;
> + }
> return op;
> }
>
> +/* Helper for the autogenerated code, get at the definition of NAME when
> + VALUEIZE allows that. */
> +
> +inline gimple *
> +get_def (tree (*valueize)(tree), tree name)
> +{
> + if (valueize && ! valueize (name))
> + return NULL;
> + return SSA_NAME_DEF_STMT (name);
> +}
I realise this is preexisting, but why do we ignore the value returned
by valueize, even if it's different from NAME? I struggled over that
with the old code when I hit the same problem with some SVE patches
(for which, thanks for the fix).
A comment might be good.
Thanks,
Richard
