* [PATCH] inliner: Don't emit copy stmts for empty type parameters [PR103989]
@ 2022-01-13 9:10 Jakub Jelinek
2022-01-13 9:54 ` Richard Biener
0 siblings, 1 reply; 3+ messages in thread
From: Jakub Jelinek @ 2022-01-13 9:10 UTC (permalink / raw)
To: Richard Biener, Jason Merrill; +Cc: gcc-patches
Hi!
The following patch avoids emitting a parameter copy statement when inlining
if the parameter has empty type. E.g. the gimplifier does something similar
(except that it needs to evaluate side-effects if any, which isn't the case
here):
/* For empty types only gimplify the left hand side and right hand
side as statements and throw away the assignment. Do this after
gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
types properly. */
if (is_empty_type (TREE_TYPE (*from_p))
&& !want_value
/* Don't do this for calls that return addressable types, expand_call
relies on those having a lhs. */
&& !(TREE_ADDRESSABLE (TREE_TYPE (*from_p))
&& TREE_CODE (*from_p) == CALL_EXPR))
{
gimplify_stmt (from_p, pre_p);
gimplify_stmt (to_p, pre_p);
*expr_p = NULL_TREE;
return GS_ALL_DONE;
}
Unfortunately, this patch doesn't cure the uninit warnings in that PR,
but I think is desirable anyway.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-01-13 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/103989
* tree-inline.c (setup_one_parameter): Don't copy parms with
empty type.
--- gcc/tree-inline.c.jj 2022-01-11 23:11:23.422275652 +0100
+++ gcc/tree-inline.c 2022-01-12 18:37:44.119950128 +0100
@@ -3608,7 +3608,7 @@ setup_one_parameter (copy_body_data *id,
init_stmt = gimple_build_assign (def, rhs);
}
}
- else
+ else if (!is_empty_type (TREE_TYPE (var)))
init_stmt = gimple_build_assign (var, rhs);
if (bb && init_stmt)
Jakub
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] inliner: Don't emit copy stmts for empty type parameters [PR103989]
2022-01-13 9:10 [PATCH] inliner: Don't emit copy stmts for empty type parameters [PR103989] Jakub Jelinek
@ 2022-01-13 9:54 ` Richard Biener
2022-01-13 10:08 ` Jakub Jelinek
0 siblings, 1 reply; 3+ messages in thread
From: Richard Biener @ 2022-01-13 9:54 UTC (permalink / raw)
To: Jakub Jelinek; +Cc: Jason Merrill, gcc-patches
On Thu, 13 Jan 2022, Jakub Jelinek wrote:
> Hi!
>
> The following patch avoids emitting a parameter copy statement when inlining
> if the parameter has empty type. E.g. the gimplifier does something similar
> (except that it needs to evaluate side-effects if any, which isn't the case
> here):
> /* For empty types only gimplify the left hand side and right hand
> side as statements and throw away the assignment. Do this after
> gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
> types properly. */
> if (is_empty_type (TREE_TYPE (*from_p))
> && !want_value
> /* Don't do this for calls that return addressable types, expand_call
> relies on those having a lhs. */
> && !(TREE_ADDRESSABLE (TREE_TYPE (*from_p))
> && TREE_CODE (*from_p) == CALL_EXPR))
> {
> gimplify_stmt (from_p, pre_p);
> gimplify_stmt (to_p, pre_p);
> *expr_p = NULL_TREE;
> return GS_ALL_DONE;
> }
> Unfortunately, this patch doesn't cure the uninit warnings in that PR,
> but I think is desirable anyway.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Hmm, but not emitting the initialization might cause even more such
warnings for the case where the passed in argument _is_ initialized
(or not visible as not, like when being a function parameter itself)?
Otherwise sure, it's the same what the gimplifier does.
I wonder if instead uninit warning should simply ignore uses of
"empty" typed variables?
OK.
Thanks,
Richard.
> 2022-01-13 Jakub Jelinek <jakub@redhat.com>
>
> PR tree-optimization/103989
> * tree-inline.c (setup_one_parameter): Don't copy parms with
> empty type.
>
> --- gcc/tree-inline.c.jj 2022-01-11 23:11:23.422275652 +0100
> +++ gcc/tree-inline.c 2022-01-12 18:37:44.119950128 +0100
> @@ -3608,7 +3608,7 @@ setup_one_parameter (copy_body_data *id,
> init_stmt = gimple_build_assign (def, rhs);
> }
> }
> - else
> + else if (!is_empty_type (TREE_TYPE (var)))
> init_stmt = gimple_build_assign (var, rhs);
>
> if (bb && init_stmt)
>
> Jakub
>
>
--
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] inliner: Don't emit copy stmts for empty type parameters [PR103989]
2022-01-13 9:54 ` Richard Biener
@ 2022-01-13 10:08 ` Jakub Jelinek
0 siblings, 0 replies; 3+ messages in thread
From: Jakub Jelinek @ 2022-01-13 10:08 UTC (permalink / raw)
To: Richard Biener; +Cc: Jason Merrill, gcc-patches
On Thu, Jan 13, 2022 at 10:54:15AM +0100, Richard Biener wrote:
> > The following patch avoids emitting a parameter copy statement when inlining
> > if the parameter has empty type. E.g. the gimplifier does something similar
> > (except that it needs to evaluate side-effects if any, which isn't the case
> > here):
> > /* For empty types only gimplify the left hand side and right hand
> > side as statements and throw away the assignment. Do this after
> > gimplify_modify_expr_rhs so we handle TARGET_EXPRs of addressable
> > types properly. */
> > if (is_empty_type (TREE_TYPE (*from_p))
> > && !want_value
> > /* Don't do this for calls that return addressable types, expand_call
> > relies on those having a lhs. */
> > && !(TREE_ADDRESSABLE (TREE_TYPE (*from_p))
> > && TREE_CODE (*from_p) == CALL_EXPR))
> > {
> > gimplify_stmt (from_p, pre_p);
> > gimplify_stmt (to_p, pre_p);
> > *expr_p = NULL_TREE;
> > return GS_ALL_DONE;
> > }
> > Unfortunately, this patch doesn't cure the uninit warnings in that PR,
> > but I think is desirable anyway.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> Hmm, but not emitting the initialization might cause even more such
> warnings for the case where the passed in argument _is_ initialized
> (or not visible as not, like when being a function parameter itself)?
Most of the time it won't be initialized either, but sure, there
can be some cases like when a larger struct is initialized with memset
and then we pass a field from that as an argument.
> Otherwise sure, it's the same what the gimplifier does.
>
> I wonder if instead uninit warning should simply ignore uses of
> "empty" typed variables?
Apparently it does already:
/* Avoid warning about empty types such as structs with no members.
The first_field() test is important for C++ where the predicate
alone isn't always sufficient. */
tree rhstype = TREE_TYPE (rhs);
if (POINTER_TYPE_P (rhstype))
rhstype = TREE_TYPE (rhstype);
if (is_empty_type (rhstype))
return NULL_TREE;
Though, the above
if (POINTER_TYPE_P (rhstype))
rhstype = TREE_TYPE (rhstype);
is just extremely suspicious, either we care about what type rhs has,
or it is dereferenced and it must be a pointer type and we care about
what it points to, but the simple fact whether rhs has a pointer type
or some other type shouldn't change what we test is_empty_type on.
When I was briefly looking at the assignment on which it actually warned,
it actually looked not empty type related.
Jakub
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-01-13 9:10 [PATCH] inliner: Don't emit copy stmts for empty type parameters [PR103989] Jakub Jelinek
2022-01-13 9:54 ` Richard Biener
2022-01-13 10:08 ` Jakub Jelinek
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