Building with Clang errors after commit 6baaeadae9 ("MIPS: Provide
unroll() macro, use it for cache ops") since the GCC_VERSION macro
is defined in include/linux/compiler-gcc.h, which is only included
in compiler.h when using GCC:
In file included from arch/mips/kernel/mips-mt.c:20:
./arch/mips/include/asm/r4kcache.h:254:1: error: use of undeclared
identifier 'GCC_VERSION'; did you mean 'S_VERSION'?
__BUILD_BLAST_CACHE(i, icache, Index_Invalidate_I, Hit_Invalidate_I, 32,
)
^
./arch/mips/include/asm/r4kcache.h:219:4: note: expanded from macro
'__BUILD_BLAST_CACHE'
cache_unroll(32, kernel_cache, indexop,
^
./arch/mips/include/asm/r4kcache.h:203:2: note: expanded from macro
'cache_unroll'
unroll(times, _cache_op, insn, op, (addr) + (i++ * (lsize)));
^
./arch/mips/include/asm/unroll.h:28:15: note: expanded from macro
'unroll'
BUILD_BUG_ON(GCC_VERSION >= 40700 && \
^
Use CONFIG_GCC_VERSION, which will always be set by Kconfig.
Additionally, Clang 8 had improvements around __builtin_constant_p so
use that as a lower limit for this check with Clang (although MIPS
wasn't buildable until Clang 9); building a kernel with Clang 9.0.0
has no issues after this change.
Fixes: 6baaeadae9 ("MIPS: Provide unroll() macro, use it for cache ops")
Link: https://github.com/ClangBuiltLinux/linux/issues/736
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: linux-mips@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: clang-built-linux@googlegroups.com
Cc: Nick Desaulniers <ndesaulniers@google.com>
Currently we have a lot of duplication in asm/r4kcache.h to handle
manually unrolling loops of cache ops for various line sizes, and we
have to explicitly handle the difference in cache op immediate width
between MIPSr6 & earlier ISA revisions with further duplication.
Introduce an unroll() macro in asm/unroll.h which expands to a switch
statement which is used to call a function or expand a preprocessor
macro a compile-time constant number of times in a row - effectively
explicitly unrolling a loop. We make use of this here to remove the
cache op duplication & will use it further in later patches.
A nice side effect of this is that calculating the cache op offset
immediate is now the compiler's responsibility, so we're no longer
sensitive to the width change of that immediate in MIPSr6 & will be
similarly agnostic to immediate width in any future supported ISA.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Nathan Chancellor