Re: [2.6 patch] add a config option for -Os compilation

[Adrian Bunk]

On Sun, Sep 14, 2003 at 01:33:49PM +0100, Russell King wrote:
> On Sun, Sep 14, 2003 at 02:16:56PM +0200, Adrian Bunk wrote:
> > The patch below adds a config option OPTIMIZE_FOR_SIZE for telling gcc 
> > to use -Os instead of -O2. Besides this, it removes constructs on 
> > architectures that had a -Os hardcoded in their Makefiles.
> 
> I'd rather retain the -Os default for ARM please.  (The init/Kconfig
> defaults it to 'n' for everything.)

Below is the patch with the ARM part omitted.

cu
Adrian

--- linux-2.6.0-test5-Os/init/Kconfig.old	2003-09-13 17:30:50.000000000 +0200
+++ linux-2.6.0-test5-Os/init/Kconfig	2003-09-13 17:30:59.000000000 +0200
@@ -65,6 +65,15 @@
 
 menu "General setup"
 
+config OPTIMIZE_FOR_SIZE
+	bool "Optimize for size" if EXPERIMENTAL
+	default n
+	help
+	  Enabling this option will pass "-Os" instead of "-O2" to gcc
+	  resulting in a smaller kernel.
+
+	  If unsure, say N.
+
 config SWAP
 	bool "Support for paging of anonymous memory"
 	depends on MMU
--- linux-2.6.0-test5-Os/Makefile.old	2003-09-13 17:30:50.000000000 +0200
+++ linux-2.6.0-test5-Os/Makefile	2003-09-13 17:30:59.000000000 +0200
@@ -223,7 +223,7 @@
 NOSTDINC_FLAGS  = -nostdinc -iwithprefix include
 
 CPPFLAGS	:= -D__KERNEL__ -Iinclude
-CFLAGS 		:= -Wall -Wstrict-prototypes -Wno-trigraphs -O2 \
+CFLAGS 		:= -Wall -Wstrict-prototypes -Wno-trigraphs \
 	  	   -fno-strict-aliasing -fno-common
 AFLAGS		:= -D__ASSEMBLY__
 
@@ -370,6 +370,12 @@
 # ---------------------------------------------------------------------------
 
 
+ifdef CONFIG_OPTIMIZE_FOR_SIZE
+CFLAGS		+= -Os
+else
+CFLAGS		+= -O2
+endif
+
 ifndef CONFIG_FRAME_POINTER
 CFLAGS		+= -fomit-frame-pointer
 endif
--- linux-2.6.0-test5-Os/arch/h8300/Makefile.old	2003-09-13 17:30:50.000000000 +0200
+++ linux-2.6.0-test5-Os/arch/h8300/Makefile	2003-09-13 17:30:59.000000000 +0200
@@ -34,7 +34,7 @@
 ldflags-$(CONFIG_CPU_H8S)	:= -mh8300self
 
 CFLAGS += $(cflags-y)
-CFLAGS += -mint32 -fno-builtin -Os
+CFLAGS += -mint32 -fno-builtin
 CFLAGS += -g
 CFLAGS += -D__linux__
 CFLAGS += -DUTS_SYSNAME=\"uClinux\"
-
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