From: Mathieu Desnoyers Date: Sat, 16 Aug 2008 07:39:26 +0000 (-0400) Subject: x86: correct register constraints for 64-bit atomic operations X-Git-Tag: v2.6.27-rc4~42^2~9 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3c3b5c3b0bf798316a410e27e3d7e6f015663602;p=pandora-kernel.git x86: correct register constraints for 64-bit atomic operations x86_64 add/sub atomic ops does not seems to accept integer values bigger than 32 bits as immediates. Intel's add/sub documentation specifies they have to be passed as registers. The only operations in the x86-64 architecture which accept arbitrary 64-bit immediates is "movq" to any register; similarly, the only operation which accept arbitrary 64-bit displacement is "movabs" to or from al/ax/eax/rax. http://gcc.gnu.org/onlinedocs/gcc-4.3.0/gcc/Machine-Constraints.html states : e 32-bit signed integer constant, or a symbolic reference known to fit that range (for immediate operands in sign-extending x86-64 instructions). Z 32-bit unsigned integer constant, or a symbolic reference known to fit that range (for immediate operands in zero-extending x86-64 instructions). Since add/sub does sign extension, using the "e" constraint seems appropriate. It applies to 2.6.27-rc, 2.6.26, 2.6.25... Signed-off-by: Mathieu Desnoyers Signed-off-by: H. Peter Anvin Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed