include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR (3e2ffd65) · Commits · 戴 / test

Since commit ("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: ("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>

include/linux/compiler-clang.h

+2 −3

Original line number	Diff line number	Diff line
		@@ -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

include/linux/compiler-gcc.h

+0 −4

Original line number	Diff line number	Diff line
		@@ -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

include/linux/compiler-intel.h

+1 −3

Original line number	Diff line number	Diff line
		@@ -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>

include/linux/compiler.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -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. */

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