From: "Michael S. Tsirkin" mst@redhat.com
[ Upstream commit 3e2ffd655cc6a694608d997738989ff5572a8266 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/compiler-clang.h | 5 ++--- include/linux/compiler-gcc.h | 4 ---- include/linux/compiler-intel.h | 4 +--- include/linux/compiler.h | 4 +++- 4 files changed, 6 insertions(+), 11 deletions(-)
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h index 3e7dafb3ea80..7ddaeb5182e3 100644 --- a/include/linux/compiler-clang.h +++ b/include/linux/compiler-clang.h @@ -3,9 +3,8 @@ #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead." #endif
-/* Some compiler specific definitions are overwritten here - * for Clang compiler - */ +/* Compiler specific definitions for Clang compiler */ + #define uninitialized_var(x) x = *(&(x))
/* same as gcc, this was present in clang-2.6 so we can assume it works diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index 977ddf2774f9..c61c4bb2bd15 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -58,10 +58,6 @@ (typeof(ptr)) (__ptr + (off)); \ })
-/* Make the optimizer believe the variable can be manipulated arbitrarily. */ -#define OPTIMIZER_HIDE_VAR(var) \ - __asm__ ("" : "=r" (var) : "0" (var)) - /* * A trick to suppress uninitialized variable warning without generating any * code diff --git a/include/linux/compiler-intel.h b/include/linux/compiler-intel.h index 517bd14e1222..b17f3cd18334 100644 --- a/include/linux/compiler-intel.h +++ b/include/linux/compiler-intel.h @@ -5,9 +5,7 @@
#ifdef __ECC
-/* Some compiler specific definitions are overwritten here - * for Intel ECC compiler - */ +/* Compiler specific definitions for Intel ECC compiler */
#include <asm/intrinsics.h>
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. */