Le 29/07/2019 à 22:32, Nathan Chancellor a écrit :
On Mon, Jul 29, 2019 at 01:25:41PM -0700, Nick Desaulniers wrote:Commit 6c5875843b87 ("powerpc: slightly improve cache helpers") exposed what looks like a codegen bug in Clang's handling of `%y` output template with `Z` constraint. This is resulting in panics during boot for 32b powerpc builds w/ Clang, as reported by our CI. Add back the original code that worked behind a preprocessor check for __clang__ until we can fix LLVM. Further, it seems that clang allnoconfig builds are unhappy with `Z`, as reported by 0day bot. This is likely because Clang warns about inline asm constraints when the constraint requires inlining to be semantically valid. Link: https://bugs.llvm.org/show_bug.cgi?id=42762 Link: https://github.com/ClangBuiltLinux/linux/issues/593 Link: https://lore.kernel.org/lkml/20190721075846.GA97701@archlinux-threadripper/ Debugged-by: Nathan Chancellor <[email protected]> Reported-by: Nathan Chancellor <[email protected]> Reported-by: kbuild test robot <[email protected]> Suggested-by: Nathan Chancellor <[email protected]> Signed-off-by: Nick Desaulniers <[email protected]> --- Alternatively, we could just revert 6c5875843b87. It seems that GCC generates the same code for these functions for out of line versions. But I'm not sure how the inlined code generated would be affected.For the record: https://godbolt.org/z/z57VU7 This seems consistent with what Michael found so I don't think a revert is entirely unreasonable.
Your example functions are too simple to show anything. The functions takes only one parameter so of course GCC won't use two registers allthough given the opportunity.
Christophe
Either way: Reviewed-by: Nathan Chancellor <[email protected]>
