On Tue, 20 Jun 2017, Mark Rutland wrote:
> As with my reply to David, my preference would be that we:
>
> 1) Align compiler-clang.h with the compiler-gcc.h inlining behaviour, so
> that things work by default.
>
> 2) Fix up the arm64 core code (and drivers for architected / common
> peripherals) to use __always_inline where we always require inlining.
>
> 3) Have arm64 select CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING, and have
> people test-build configurations with CONFIG_OPTIMIZE_INLINING, with
> both GCC and clang.
>
> 4) Fix up drivers, etc, as appropriate.
>
> 5) Once that's largely stable, and if there's a benefit, have arm64
> select CONFIG_OPTIMIZE_INLINING by default.
>
> That should avoid undue breakage, while enabling this ASAP.
>
Sounds good, but I think we should simply deal with the
__attribute__((unused)) needed for clang as part of compiler-gcc.h by
simply adding it to the inline override there to avoid duplicated code.
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -15,11 +15,3 @@
* with any version that can compile the kernel
*/
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
-
-/*
- * GCC does not warn about unused static inline functions for
- * -Wunused-function. This turns out to avoid the need for complex #ifdef
- * directives. Suppress the warning in clang as well.
- */
-#undef inline
-#define inline inline __attribute__((unused)) notrace
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 0efef9cf014f..71fe0994cf1a 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -66,18 +66,22 @@
/*
* Force always-inline if the user requests it so via the .config,
- * or if gcc is too old:
+ * or if gcc is too old.
+ * GCC does not warn about unused static inline functions for
+ * -Wunused-function. This turns out to avoid the need for complex #ifdef
+ * directives. Suppress the warning in clang as well by using "unused"
+ * function attribute, which is redundant but not harmful for gcc.
*/
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
!defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
-#define inline inline __attribute__((always_inline)) notrace
-#define __inline__ __inline__ __attribute__((always_inline)) notrace
-#define __inline __inline __attribute__((always_inline)) notrace
+#define inline inline __attribute__((always_inline,unused)) notrace
+#define __inline__ __inline__ __attribute__((always_inline,unused)) notrace
+#define __inline __inline __attribute__((always_inline,unused)) notrace
#else
/* A lot of inline functions can cause havoc with function tracing */
-#define inline inline notrace
-#define __inline__ __inline__ notrace
-#define __inline __inline notrace
+#define inline inline __attribute__((unused)) notrace
+#define __inline__ __inline__ __attribute__((unused)) notrace
+#define __inline __inline __attribute__((unused)) notrace
#endif
#define __always_inline inline __attribute__((always_inline))
