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Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.
[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
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CONFIG_CC_IS_GCC is undefined when Clang is used, which breaks the build
(see our Travis link below).
Clang 8 was chosen as a minimum version for this check because there
were some improvements around __builtin_constant_p in that release. In
reality, MIPS was not even buildable until clang 9 so that check was not
technically necessary. Just remove all compiler checks and just assume
that we have a working compiler.
Fixes: d4e60453266b ("Restore gcc check in mips asm/unroll.h")
Link: https://travis-ci.com/github/ClangBuiltLinux/continuous-integration/jobs/359642821
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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While raising the gcc version requirement to 4.9, the compile-time check
in the unroll macro was accidentally changed from being used on gcc and
clang to being used on clang only.
Restore the gcc check, changing it from "gcc >= 4.7" to "all gcc".
[ We should probably remove this all entirely: if we remove the check
for CLANG, then the check for GCC can go away. Older versions of clang
are not really appropriate or supported for kernel builds - Linus ]
Fixes: 6ec4476ac825 ("Raise gcc version requirement to 4.9")
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.eti.br>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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I realize that we fairly recently raised it to 4.8, but the fact is, 4.9
is a much better minimum version to target.
We have a number of workarounds for actual bugs in pre-4.9 gcc versions
(including things like internal compiler errors on ARM), but we also
have some syntactic workarounds for lacking features.
In particular, raising the minimum to 4.9 means that we can now just
assume _Generic() exists, which is likely the much better replacement
for a lot of very convoluted built-time magic with conditionals on
sizeof and/or __builtin_choose_expr() with same_type() etc.
Using _Generic also means that you will need to have a very recent
version of 'sparse', but thats easy to build yourself, and much less of
a hassle than some old gcc version can be.
The latest (in a long string) of reasons for minimum compiler version
upgrades was commit 5435f73d5c4a ("efi/x86: Fix build with gcc 4").
Ard points out that RHEL 7 uses gcc-4.8, but the people who stay back on
old RHEL versions persumably also don't build their own kernels anyway.
And maybe they should cross-built or just have a little side affair with
a newer compiler?
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Building with Clang errors after commit 6baaeadae911 ("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: 6baaeadae911 ("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>
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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
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Gustavo A. R. Silva
Nathan Chancellor
Cesar Eduardo Barros
Linus Torvalds
Paul Burton