diff options
| author | Marc Mutz <marc.mutz@kdab.com> | 2012-08-24 12:40:20 +0200 |
|---|---|---|
| committer | Qt by Nokia <qt-info@nokia.com> | 2012-08-26 16:54:23 +0200 |
| commit | 56603a8d83762d15e37c887e4c66a340d679f316 (patch) | |
| tree | 15d077eb34ee23c43fa31ca9dc5d370bb268d110 | |
| parent | e6c50609c8a098304ab6b2a41aa371563ba45d2e (diff) | |
QMetaTypeId: optimize qt_metatype_id()
The old code resulted in one memory fetch for the test plus another one
for the return value (at the assembler level). The new code reuses the
already-loaded value:
- movl _ZZN11QMetaTypeIdI12QDBusMessageE14qt_metatype_idEvE11metatype_id(%rip), %edx
- testl %edx, %edx
- je .L158
movl _ZZN11QMetaTypeIdI12QDBusMessageE14qt_metatype_idEvE11metatype_id(%rip), %eax
- ret
+ testl %eax, %eax
+ je .L160
+ rep; ret
It also saves one load in the not-yet-initialised case:
-.L158:
+.L160:
leaq .LC7(%rip), %rdi
subq , %rsp
.cfi_def_cfa_offset 16
movq himBH1, %rsi
call _Z17qRegisterMetaTypeI12QDBusMessageEiPKcPT_
movl %eax, _ZZN11QMetaTypeIdI12QDBusMessageE14qt_metatype_idEvE11metatype_id(%rip)
- movl _ZZN11QMetaTypeIdI12QDBusMessageE14qt_metatype_idEvE11metatype_id(%rip), %eax
addq , %rsp
.cfi_def_cfa_offset 8
ret
Change-Id: I769950449822f2b1587680e05518be0a4f3120a2
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
| -rw-r--r-- | src/corelib/kernel/qmetatype.h | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h index 8af3ce9024..80bc4a48b7 100644 --- a/src/corelib/kernel/qmetatype.h +++ b/src/corelib/kernel/qmetatype.h @@ -690,10 +690,12 @@ inline int qRegisterMetaTypeStreamOperators() static int qt_metatype_id() \ { \ static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \ - if (!metatype_id.load()) \ - metatype_id.storeRelease(qRegisterMetaType< TYPE >(#TYPE, \ - reinterpret_cast< TYPE *>(quintptr(-1)))); \ - return metatype_id.loadAcquire(); \ + if (const int id = metatype_id.loadAcquire()) \ + return id; \ + const int newId = qRegisterMetaType< TYPE >(#TYPE, \ + reinterpret_cast< TYPE *>(quintptr(-1))); \ + metatype_id.storeRelease(newId); \ + return newId; \ } \ }; \ QT_END_NAMESPACE |