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| author | Michael S. Tsirkin <mst@redhat.com> | 2019-01-02 15:57:49 -0500 |
|---|---|---|
| committer | Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> | 2019-01-09 11:36:41 +0100 |
| commit | 3e2ffd655cc6a694608d997738989ff5572a8266 (patch) | |
| tree | 404f9e5008513f378ebfb74b94e8723ca63113b5 /include/linux/compiler.h | |
| parent | bfeffd155283772bbe78c6a05dec7c0128ee500c (diff) | |
| download | lwn-3e2ffd655cc6a694608d997738989ff5572a8266.tar.gz lwn-3e2ffd655cc6a694608d997738989ff5572a8266.zip | |
include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR
Since commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") clang no longer reuses the OPTIMIZER_HIDE_VAR macro
from compiler-gcc - instead it gets the version in
include/linux/compiler.h. Unfortunately that version doesn't actually
prevent compiler from optimizing out the variable.
Fix up by moving the macro out from compiler-gcc.h to compiler.h.
Compilers without incline asm support will keep working
since it's protected by an ifdef.
Also fix up comments to match reality since we are no longer overriding
any macros.
Build-tested with gcc and clang.
Fixes: 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Cc: Eli Friedman <efriedma@codeaurora.org>
Cc: Joe Perches <joe@perches.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Diffstat (limited to 'include/linux/compiler.h')
| -rw-r--r-- | include/linux/compiler.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index fc5004a4b07d..445348facea9 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -161,7 +161,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #endif #ifndef OPTIMIZER_HIDE_VAR -#define OPTIMIZER_HIDE_VAR(var) barrier() +/* Make the optimizer believe the variable can be manipulated arbitrarily. */ +#define OPTIMIZER_HIDE_VAR(var) \ + __asm__ ("" : "=r" (var) : "0" (var)) #endif /* Not-quite-unique ID. */ |