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Message-ID: <50EA1C9B.8040304@opensuse.org> Date: Sun, 06 Jan 2013 21:53:47 -0300 From: Cristian Rodríguez <crrodriguez@...nsuse.org> To: Theodore Ts'o <tytso@....edu> CC: linux-ext4@...r.kernel.org Subject: Re: [PATCH] lib/ext2fs: Use __builtin_popcount when available Signed-off-by: Cristian Rodríguez <crrodriguez@...nsuse.org> El dom 06 ene 2013 19:20:20 CLST, Theodore Ts'o escribió: > I could imagine a patch which explicitly checks the CPU type using the > x86 cpuinfo instructure, and only optionally uses the popcount > instruction if it exists, and uses the optimized code if it doesn't, > but then again, it's not clear how much it's worth it. The first incarnation of this patch did exactly that, too ugly didnt not send it. ;) > Better yet would be if gcc was taught how to recognize the C > statements in popcount32(), since that's one of the standard, > intelligent ways of implementing popcount32 (as opposed to the stupid > way which is apparently used by gcc's runtime library, sigh), and > inserted code which automatically did the cpuinfo check and fallback > to popcount if the CPU supports it. This would be even better since > then gcc could do a single cpuinfo check, and then automatically use > the faster SSE[234] instructions as necessary, without having to ask > application programmers to put in gcc-specific __builtin_* functions Yeah, I asked GCC developers exactly this, was told to fill a enhancement request. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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