On Thu, Mar 22, 2018 at 4:58 PM Matthias Kaehlcke <[email protected]> wrote:
> El Thu, Mar 22, 2018 at 04:19:42PM -0700 Greg Hackmann ha dit: > > NAK. There's a reason I didn't send my change upstream. > > > > As Marc pointed out (https://lkml.org/lkml/2018/3/16/987), the "r" > > prefix tells gcc to pick the appropriate register width. "x" makes it > > unconditionally use the entire 64-bit register width. Just swapping out > > one for the other changes the macro's semantics. > > > > Unfortunately since this was breaking builds in android-4.14 and we > > didn't have an immediate-term fix, I bit the bullet and added the above > > commit -- but *only* as a short-term workaround. For the one caller we > > currently have in 4.14.y, gcc was using the entire 64-bit width for all > > its inputs anyway, so "r" vs. "x" didn't make a difference. But that > > might not be true if/when someone introduces other SMCCC 1.1 callers. > > > > Unfortunately I don't see a better way to deal with this than waiting > > for clang to support "r"-style constraints on ARM64. > Thanks for the clarification! From the other thread > (https://lkml.org/lkml/2018/3/1/268) I had the impression that ARM > folks saw the option of a mergeable fix. > Given the fact that clang support for kernel builds is still > recent/WIP I guess it's not the end of the world if we have to raise > the minimum clang version to 7.x for newer kernels. Manoj fixed this in: https://reviews.llvm.org/rL328829 https://bugs.llvm.org/show_bug.cgi?id=36862 Looks set to ride the Clang 6.0 train. mka@ if you're planning another state of the union email, it would be good to note the clang 6.0 requirement for arm64. Is there anything left to do here? -- Thanks, ~Nick Desaulniers
