On Fri, Feb 12, 2021 at 7:27 AM Peter Zijlstra <[email protected]> wrote: > > On Fri, Feb 12, 2021 at 09:40:59AM -0500, Steven Rostedt wrote: > > On Thu, 11 Feb 2021 13:48:48 -0800 > > Jason Gerecke <[email protected]> wrote: > > > > > When compiling an external kernel module with `-O0` or `-O1`, the > > > following > > > compile error may be reported: > > > > > > ./arch/x86/include/asm/jump_label.h:25:2: error: impossible > > > constraint in ‘asm’ > > > 25 | asm_volatile_goto("1:" > > > | ^~~~~~~~~~~~~~~~~ > > > > > > It appears that these lower optimization levels prevent GCC from detecting > > > that the key/branch arguments can be treated as constants and used as > > > immediate operands. To work around this, explicitly add the `const` label. > > > > Yes this makes sense. The "i" constraint needs to be a constant. > > Right, using -O[01] seems a little daft though. But yeah, that patch is > correct and won't cause harm. > > I've queued it for after the next merge window.
Thanks. Only reason I even tried compiling at those levels was to play around with GCC's new static analyzer options. They seem to be ineffective at more normal optimization levels.
