ZEN: Restore CONFIG_OPTIMIZE_FOR_PERFORMANCE_O3

This reverts a6036a4 (kbuild: drop
support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3), removes the
dependency on CONFIG_ARC and adds RUSTFLAGS.

Signed-off-by: Simão Gomes Viana <[email protected]>

Author: heftig

Makefile

@@ -802,6 +802,9 @@ 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

@@ -1458,6 +1458,12 @@ 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)"
+	help
+	  Choosing this option will pass "-O3" to your compiler to optimize
+	  the kernel yet more for performance.
+
 config CC_OPTIMIZE_FOR_SIZE
 	bool "Optimize for size (-Os)"
 	help