Hi!
As discussed in the
https://gcc.gnu.org/pipermail/gcc-patches/2025-January/674492.html
thread, the following patch attempts to improve build_vec_init generated
code. E.g. on g++.dg/eh/aggregate1.C test the patch has differences like:
D.2988 = &D.2950->e1;
D.2989 = D.2988;
D.2990 = 1;
try
{
goto <D.2996>;
<D.2997>:
A::A (D.2989);
D.2990 = D.2990 + -1;
D.2989 = D.2989 + 1;
<D.2996>:
if (D.2990 >= 0) goto <D.2997>; else goto <D.2995>;
<D.2995>:
retval.4 = D.2988;
_13 = &D.2950->e2;
A::A (_13);
- D.2990 = 1;
+ D.2988 = 0B;
D.2951 = D.2951 + -1;
}
catch
{
{
struct A * D.2991;
if (D.2988 != 0B) goto <D.3028>; else goto
<D.3029>;
<D.3028>:
_11 = 1 - D.2990;
_12 = (sizetype) _11;
D.2991 = D.2988 + _12;
<D.3030>:
if (D.2991 == D.2988) goto <D.3031>; else goto
<D.3032>;
<D.3032>:
D.2991 = D.2991 + 18446744073709551615;
A::~A (D.2991);
goto <D.3030>;
<D.3031>:
goto <D.3033>;
<D.3029>:
<D.3033>:
}
}
in 3 spots. As you can see, both setting D.2990 (i.e. iterator) to
maxindex and setting D.2988 (i.e. rval) to nullptr have the same effect of
not actually destructing anything anymore in the cleanup, the
advantage of clearing rval is that setting something to zero is often less
expensive than potentially huge maxindex and that the cleanup tests that
value first.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2025-04-30 Jakub Jelinek <ja...@redhat.com>
PR c++/117827
* init.cc (build_vec_init): Push to *cleanup_flags clearing of rval
instead of setting of iterator to maxindex.
--- gcc/cp/init.cc.jj 2025-01-24 19:26:31.980193087 +0100
+++ gcc/cp/init.cc 2025-01-24 19:45:03.324702001 +0100
@@ -4749,7 +4749,8 @@ build_vec_init (tree base, tree maxindex
itself. But that breaks when gimplify_target_expr adds a clobber
cleanup that runs before the build_vec_init cleanup. */
if (cleanup_flags)
- vec_safe_push (*cleanup_flags, build_tree_list (iterator, maxindex));
+ vec_safe_push (*cleanup_flags,
+ build_tree_list (rval, build_zero_cst (ptype)));
}
/* Should we try to create a constant initializer? */
Jakub
