From ce487aab46e72641b4fcc3b77c07c7a54c833368 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Mon, 29 Oct 2018 16:09:57 +0100 Subject: [PATCH] BUG/MEDIUM: tools: fix direction of my_ffsl() Commit 27346b01a ("OPTIM: tools: optimize my_ffsl() for x86_64") optimized my_ffsl() for intensive use cases in the scheduler, but as half of the times I got it wrong so it counted bits the reverse way. It doesn't matter for the scheduler nor fd cache but it broke cpu-map with threads which heavily relies on proper ordering. We should probably consider dropping support for gcc < 3.4 and switching to builtins for these ones, though often they are as ambiguous. No backport is needed. --- include/common/standard.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/common/standard.h b/include/common/standard.h index 3f8d2d0729..53d7f9f3b3 100644 --- a/include/common/standard.h +++ b/include/common/standard.h @@ -815,7 +815,7 @@ static inline unsigned int my_ffsl(unsigned long a) unsigned long cnt; #if defined(__x86_64__) - __asm__("bsr %1,%0\n" : "=r" (cnt) : "rm" (a)); + __asm__("bsf %1,%0\n" : "=r" (cnt) : "rm" (a)); cnt++; #else -- 2.39.5