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QFontEngine: reduce unnecessary relocations

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Instead of static constexpr QL1SV objects (which force the compiler to
allocate storage for them and therefore cause relocations), use mere
automatic constexpr objects (which don't). There never was a need to
make these objects static, as constexpr is enough to force the
compiler to constant-fold them.

Difference:
  qfontengine.cpp.o:
- 0000000000000040 l     O .data.rel.ro.local     0000000000000010 QFontEngine::findGlyph(QLatin1String) const::gid
- 0000000000000000 l     O .data.rel.ro.local     0000000000000010 QFontEngine::findGlyph(QLatin1String) const::uni
  0000000000000000 l    d  .data.rel.ro.local     0000000000000000 .data.rel.ro.local

See
  https://stackoverflow.com/questions/19067010/finding-where-relocations-originate/19338343#19338343
for the script to generate this output.

See https://www.akkadia.org/drepper/dsohowto.pdf Section 1.6 for why
we care.

Amends 176816f21324bf736389037c62538a25f2522808.

Pick-to: 6.9
Task-number: QTBUG-100536
Change-Id: I3cdf42c9758ec32654b378a2b27b565a6c92c26b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Anton Kudryavtsev <antkudr@mail.ru>
This commit is contained in:
Marc Mutz 2025-03-06 12:04:39 +01:00 committed by Volker Hilsheimer
parent 1370ecf293
commit 511ee39570
1 changed files with 2 additions and 2 deletions
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4
src/gui/text/qfontengine.cpp
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@ -949,8 +949,8 @@ glyph_t QFontEngine::findGlyph(QLatin1StringView name) const
#endif
if (!result) {
static constexpr auto gid = "gid"_L1;
static constexpr auto uni = "uni"_L1;
constexpr auto gid = "gid"_L1;
constexpr auto uni = "uni"_L1;
if (name.startsWith(gid)) {
bool ok;
result = name.slice(gid.size()).toUInt(&ok);