On 6/9/22 15:37, Patrick Palka wrote:
On Thu, 9 Jun 2022, Jason Merrill wrote:
On 6/9/22 09:00, Patrick Palka wrote:
This performs one of the optimizations added by the previous
patch to lookup_template_class, to instantiate_template as well.
(For the libstdc++ ranges tests this optimization appears to be
effective around 30% of the time, i.e. 30% of the time context of 'tmpl'
is non-dependent while the context of 'gen_tmpl' is dependent.)
If this is a significant optimization, how about doing it in tsubst_aggr_type
rather than its callers?
I'm not sure how we'd do this optimization in tsubst_aggr_type?
Oops, I was overlooking the gen_tmpl vs. tmpl difference.
I haven't observed any significant time/memory improvements based on my
limited benchmarking, but I can imagine for deeply nested templates it
could be significant. And avoiding redundant work should hopefully help
streamline debugging I suppose.
OK.
gcc/cp/ChangeLog:
* pt.cc (instantiate_template): Don't substitute the context
of the most general template if that of the partially
instantiated template is non-dependent.
---
gcc/cp/pt.cc | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index e021c254872..208daad298a 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -21661,8 +21661,14 @@ instantiate_template (tree tmpl, tree orig_args,
tsubst_flags_t complain)
++processing_template_decl;
if (DECL_CLASS_SCOPE_P (gen_tmpl))
{
- tree ctx = tsubst_aggr_type (DECL_CONTEXT (gen_tmpl), targ_ptr,
- complain, gen_tmpl, true);
+ tree ctx;
+ if (!uses_template_parms (DECL_CONTEXT (tmpl)))
+ /* If the context of the partially instantiated template is already
+ non-dependent, then we might as well use it. */
+ ctx = DECL_CONTEXT (tmpl);
+ else
+ ctx = tsubst_aggr_type (DECL_CONTEXT (gen_tmpl), targ_ptr,
+ complain, gen_tmpl, true);
push_nested_class (ctx);
}
