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clang doesn't like s390 specific inline assembler constraints. These are present in our arch specific uapi/asm/swab.h which again is required by some ebpf test cases. For current compiler versions the generic swab.h already makes use of gcc's builtin functions. Therefore we can simply remove our own header file and use the generic one. This will generate worse code if used with compilers before gcc 4.8, which has no __builtin_bswap16(); or before gcc v4.4, which has no __builtin_bswap[32|64](). For these cases a C implementation fallback would be used which generates more code, but is still correct (170KB extra code for gcc 4.3 with performance_defconfig). However given that we need (and want) to get rid of the inline assemblies anyway in order to be able to use clang, the above is just a minor drawback if old gcc compilers are used. With current compilers there is close to zero difference, except for three btrfs bit functions which generate more out-of-line code. The generated code looks still correct and also uses the s390 specific byteswap instructions. Reported-and-tested-by: Thomas Richter <tmricht@linux.vnet.ibm.com> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.