On 10/3/24 12:38 PM, Jason Merrill wrote:
On 10/2/24 7:50 AM, Richard Biener wrote:
This reduces peak memory usage by 20% for a specific testcase.
Bootstrapped and tested on x86_64-unknown-linux-gnu.
It's very ugly so I'd appreciate suggestions on how to handle such
situations better?
I'm pushing this alternative patch, tested x86_64-pc-linux-gnu.
OK, apparently that was both too clever and not clever enough.
Replacing it with this one that's much closer to yours.
Jason
From d77f073ce66cedbcbb22357c49b9ef19e1b61a43 Mon Sep 17 00:00:00 2001
From: Jason Merrill <ja...@redhat.com>
Date: Thu, 3 Oct 2024 16:31:00 -0400
Subject: [PATCH] c++: free garbage vec in coerce_template_parms
To: gcc-patches@gcc.gnu.org
coerce_template_parms can create two different vecs for the inner template
arguments, new_inner_args and (potentially) the result of
expand_template_argument_pack. One or the other, or possibly both, end up
being garbage: in the typical case, the expanded vec is garbage because it's
only used as the source for convert_template_argument. In some dependent
cases, the new vec is garbage because we decide to return the original args
instead. In these cases, ggc_free the garbage vec to reduce the memory
overhead of overload resolution.
gcc/cp/ChangeLog:
* pt.cc (coerce_template_parms): Free garbage vecs.
Co-authored-by: Richard Biener <rguent...@suse.de>
---
gcc/cp/pt.cc | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 20affcd65a2..4ceae1d38de 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -9275,6 +9275,7 @@ coerce_template_parms (tree parms,
{
/* We don't know how many args we have yet, just use the
unconverted (and still packed) ones for now. */
+ ggc_free (new_inner_args);
new_inner_args = orig_inner_args;
arg_idx = nargs;
break;
@@ -9329,7 +9330,8 @@ coerce_template_parms (tree parms,
= make_pack_expansion (conv, complain);
/* We don't know how many args we have yet, just
- use the unconverted ones for now. */
+ use the unconverted (but unpacked) ones for now. */
+ ggc_free (new_inner_args);
new_inner_args = inner_args;
arg_idx = nargs;
break;
@@ -9442,6 +9444,12 @@ coerce_template_parms (tree parms,
SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (new_inner_args,
TREE_VEC_LENGTH (new_inner_args));
+ /* If we expanded packs in inner_args and aren't returning it now, the
+ expanded vec is garbage. */
+ if (inner_args != new_inner_args
+ && inner_args != orig_inner_args)
+ ggc_free (inner_args);
+
return return_full_args ? new_args : new_inner_args;
}
--
2.46.2
