deepin: kbuild: Reapply support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANC…

…E_O3

1. Revert (a6036a4
   "kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3")
2. Mark -O3 as experimental, as it might cause unwanted regressions for
   users.
3. Allow all architectures to use the experimental -O3 optimization
   option. Previously, only ARC was allowed to use this option.

Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Oleksandr Natalenko <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Miko Larsson <[email protected]>
Signed-off-by: WangYuli <[email protected]>

Makefile

@@ -819,6 +819,9 @@ KBUILD_CFLAGS	+= -fno-delete-null-pointer-checks
 ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
 KBUILD_CFLAGS += -O2
 KBUILD_RUSTFLAGS += -Copt-level=2
+else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
+KBUILD_CFLAGS += -O3
+KBUILD_RUSTFLAGS += -Copt-level=3
 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
 KBUILD_CFLAGS += -Os
 KBUILD_RUSTFLAGS += -Copt-level=s

init/Kconfig

@@ -1377,6 +1377,15 @@ config CC_OPTIMIZE_FOR_PERFORMANCE
 	  with the "-O2" compiler flag for best performance and most
 	  helpful compile-time warnings.
 
+config CC_OPTIMIZE_FOR_PERFORMANCE_O3
+       bool "Optimize more for performance (-O3) (EXPERIMENTAL)"
+       help
+         Choosing this option will pass "-O3" to your compiler to optimize
+         the kernel yet more for performance.
+
+	  This option is EXPERIMENTAL; you may encounter compiler bugs and/or
+	  kernel bugs with this option enabled.
+
 config CC_OPTIMIZE_FOR_SIZE
 	bool "Optimize for size (-Os)"
 	help