compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING

Commit 60a3cdd06394 ("x86: add optimized inlining") introduced
CONFIG_OPTIMIZE_INLINING, but it has been available only for x86.

The idea is obviously arch-agnostic.  This commit moves the config entry
from arch/x86/Kconfig.debug to lib/Kconfig.debug so that all
architectures can benefit from it.

This can make a huge difference in kernel image size especially when
CONFIG_OPTIMIZE_FOR_SIZE is enabled.

For example, I got 3.5% smaller arm64 kernel for v5.1-rc1.

  dec       file
  18983424  arch/arm64/boot/Image.before
  18321920  arch/arm64/boot/Image.after

This also slightly improves the "Kernel hacking" Kconfig menu as
e61aca5158a8 ("Merge branch 'kconfig-diet' from Dave Hansen') suggested;
this config option would be a good fit in the "compiler option" menu.

Link: http://lkml.kernel.org/r/20190423034959.13525-12-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Borislav Petkov <bp@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 15 insertions, 19 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 818b361094ed..326b2d5bab9d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -305,9 +305,6 @@ config ZONE_DMA32
 config AUDIT_ARCH
         def_bool y if X86_64
 
-config ARCH_SUPPORTS_OPTIMIZED_INLINING
-        def_bool y
-
 config ARCH_SUPPORTS_DEBUG_PAGEALLOC
         def_bool y
 
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 15d0fbe27872..f730680dc818 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -266,20 +266,6 @@ config CPA_DEBUG
         ---help---
           Do change_page_attr() self-tests every 30 seconds.
 
-config OPTIMIZE_INLINING
-        bool "Allow gcc to uninline functions marked 'inline'"
-        ---help---
-          This option determines if the kernel forces gcc to inline the functions
-          developers have marked 'inline'. Doing so takes away freedom from gcc to
-          do what it thinks is best, which is desirable for the gcc 3.x series of
-          compilers. The gcc 4.x series have a rewritten inlining algorithm and
-          enabling this option will generate a smaller kernel there. Hopefully
-          this algorithm is so good that allowing gcc 4.x and above to make the
-          decision will become the default in the future. Until then this option
-          is there to test gcc for this.
-
-          If unsure, say N.
-
 config DEBUG_ENTRY
         bool "Debug low-level entry code"
         depends on DEBUG_KERNEL
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index ba814f18cb4c..19e58b9138a0 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -140,8 +140,7 @@ struct ftrace_likely_data {
  * Do not use __always_inline here, since currently it expands to inline again
  * (which would break users of __always_inline).
  */
-#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
-        !defined(CONFIG_OPTIMIZE_INLINING)
+#if !defined(CONFIG_OPTIMIZE_INLINING)
 #define inline inline __attribute__((__always_inline__)) __gnu_inline \
         __maybe_unused notrace
 #else
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d695ec1477f3..d5411a7484f6 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -318,6 +318,20 @@ config HEADERS_CHECK
           exported to $(INSTALL_HDR_PATH) (usually 'usr/include' in
           your build tree), to make sure they're suitable.
 
+config OPTIMIZE_INLINING
+        bool "Allow compiler to uninline functions marked 'inline'"
+        help
+          This option determines if the kernel forces gcc to inline the functions
+          developers have marked 'inline'. Doing so takes away freedom from gcc to
+          do what it thinks is best, which is desirable for the gcc 3.x series of
+          compilers. The gcc 4.x series have a rewritten inlining algorithm and
+          enabling this option will generate a smaller kernel there. Hopefully
+          this algorithm is so good that allowing gcc 4.x and above to make the
+          decision will become the default in the future. Until then this option
+          is there to test gcc for this.
+
+          If unsure, say N.
+
 config DEBUG_SECTION_MISMATCH
         bool "Enable full Section mismatch analysis"
         help