From c4e50e500da7692aad53a4488aff32e056149b3c Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Wed, 9 Jun 2021 17:48:14 -0400
Subject: [PATCH] c++: speed up looking up the current class
While looking at template instantiation tracing, I noticed that we were
frequently looking up a particular class template instance while
instantiating it. This patch shortcuts that lookup, and speeds up compiling
stdc++.h with my (checking/unoptimized) compiler by about 3%.
gcc/cp/ChangeLog:
* pt.c (lookup_template_class_1): Shortcut current_class_type.
---
gcc/cp/pt.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 141388ad2e5a..d4bb5cc5eafc 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -9833,6 +9833,13 @@ lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
/* From here on, we're only interested in the most general
template. */
+ /* Shortcut looking up the current class scope again. */
+ if (current_class_type)
+ if (tree ti = CLASSTYPE_TEMPLATE_INFO (current_class_type))
+ if (gen_tmpl == most_general_template (TI_TEMPLATE (ti))
+ && comp_template_args (arglist, TI_ARGS (ti)))
+ return current_class_type;
+
/* Calculate the BOUND_ARGS. These will be the args that are
actually tsubst'd into the definition to create the
instantiation. */
--
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