vcl/source/gdi/CommonSalLayout.cxx | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
New commits:
commit baf6c57496fe38c5ee4ab34829aaf4d4d6598d28
Author: Luboš Luňák <l.lu...@collabora.com>
AuthorDate: Tue Mar 15 08:45:59 2022 +0100
Commit: Luboš Luňák <l.lu...@collabora.com>
CommitDate: Tue Mar 15 14:39:03 2022 +0100
faster comparison of very long strings (tdf#147284)
Comparing long string backwards is inefficient because forward
compare has better memory prefetch. For the PDF export
of the document this drops the comparison cost to 1% from 6%.
Change-Id: Ide29608bf56915cc528e6ec8b98ccf8ebf4693a9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/131579
Reviewed-by: Luboš Luňák <l.lu...@collabora.com>
Tested-by: Luboš Luňák <l.lu...@collabora.com>
diff --git a/vcl/source/gdi/CommonSalLayout.cxx
b/vcl/source/gdi/CommonSalLayout.cxx
index e26dc68692bf..c4217e21a985 100644
--- a/vcl/source/gdi/CommonSalLayout.cxx
+++ b/vcl/source/gdi/CommonSalLayout.cxx
@@ -167,11 +167,27 @@ struct FirstCharsStringHash
}
};
+struct ForwardStringCompareEqual
+{
+ bool operator()( const OUString& str1, const OUString& str2 ) const
+ {
+ // Strings passed to GenericSalLayout::CreateTextLayoutCache() may be
very long,
+ // and OUString operator == compares backwards, which is inefficient
for very long
+ // strings (bad memory prefetch).
+ if( str1.getLength() != str2.getLength())
+ return false;
+ if( str1.getStr() == str2.getStr())
+ return true;
+ return memcmp( str1.getStr(), str2.getStr(), str1.getLength() *
sizeof( str1.getStr()[ 0 ] )) == 0;
+ }
+};
+
} // namespace
std::shared_ptr<const vcl::text::TextLayoutCache>
GenericSalLayout::CreateTextLayoutCache(OUString const& rString)
{
- typedef o3tl::lru_map<OUString, std::shared_ptr<const
vcl::text::TextLayoutCache>, FirstCharsStringHash> Cache;
+ typedef o3tl::lru_map<OUString, std::shared_ptr<const
vcl::text::TextLayoutCache>,
+ FirstCharsStringHash, ForwardStringCompareEqual> Cache;
static vcl::DeleteOnDeinit< Cache > cache( 1000 );
if( Cache* map = cache.get())
{
