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From: Fangrui Song <maskray@sourceware.org> To: glibc-cvs@sourceware.org Subject: [glibc/maskray/clang] i386: Explain why __HAVE_64B_ATOMICS has to be 0 Date: Tue, 2 Nov 2021 20:00:23 +0000 (GMT) [thread overview] Message-ID: <20211102200023.2CF1C3858005@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=cca75bd8b53b82d80299b03b368355b158832c9a commit cca75bd8b53b82d80299b03b368355b158832c9a Author: Florian Weimer <fweimer@redhat.com> Date: Tue Nov 2 10:26:23 2021 +0100 i386: Explain why __HAVE_64B_ATOMICS has to be 0 Diff: --- sysdeps/x86/atomic-machine.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sysdeps/x86/atomic-machine.h b/sysdeps/x86/atomic-machine.h index 695222e4fa..2692d94a92 100644 --- a/sysdeps/x86/atomic-machine.h +++ b/sysdeps/x86/atomic-machine.h @@ -60,6 +60,10 @@ typedef uintmax_t uatomic_max_t; # define BR_CONSTRAINT "q" # define IBR_CONSTRAINT "iq" #else +/* Since the Pentium, i386 CPUs have supported 64-bit atomics, but the + i386 psABI supplement provides only 4-byte alignment for uint64_t + inside structs, so it is currently not possible to use 64-bit + atomics on this platform. */ # define __HAVE_64B_ATOMICS 0 # define SP_REG "esp" # define SEG_REG "gs"
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