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[Tcl-bugs] [ tcl-Bugs-3064962 ] Suboptimal linkage of stubbed functions
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From: SourceForge.net <no...@so...> - 2010-09-13 08:17:48
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Bugs item #3064962, was opened at 2010-09-13 01:06 Message generated for change (Comment added) made by ferrieux You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=110894&aid=3064962&group_id=10894 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: 53. Configuration and Build Tools Group: None Status: Open Resolution: None Priority: 9 Private: No Submitted By: Alexandre Ferrieux (ferrieux) Assigned to: Don Porter (dgp) Summary: Suboptimal linkage of stubbed functions Initial Comment: When looking in detail at the native code generated by gcc on x86, one sees that stubbed functions, that get the EXTERN class (extern + attribute(visibility=default)), are _always_ called through the PLT (program linkage table), doing an unwanted indirection with possible strong cache misses. I don't know why it is so, because the build system uses -fvisibility=hidden, so that all those symbols should stay hidden and avoid the PLT. But the net result is a very measurable performance hit, as illustrated by in the tclcore discussion http://code.activestate.com/lists/tcl-core/9531/ ---------------------------------------------------------------------- >Comment By: Alexandre Ferrieux (ferrieux) Date: 2010-09-13 10:17 Message: Update: it's no longer mysterious, "visibility=default" meaning "not hidden". But the issue remains, and as kbk suggests the fix could very well be the -Bdynamic linker option. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=110894&aid=3064962&group_id=10894 |