kbuild: make cc-version available in kbuild files

Move $(CC) support functions to Kbuild.include so they are available
in the kbuild files.
In addition the following was done:
	o as-option documented in Documentation/kbuild/makefiles.txt
	o Moved documentation to new section to match
	  new scope of functions
	o added cc-ifversion used to conditionally select a text string
	  dependent on actual $(CC) version
	o documented cc-ifversion
	o change so Kbuild.include is read before the kbuild file

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 97 insertions, 69 deletions

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 443230b43e0..99d51a5bb0d 100644
--- a/Documentation/kbuild/makefiles.txt
+++ b/Documentation/kbuild/makefiles.txt
@@ -17,6 +17,7 @@ This document describes the Linux kernel Makefiles.
 	   --- 3.8 Command line dependency
 	   --- 3.9 Dependency tracking
 	   --- 3.10 Special Rules
+	   --- 3.11 $(CC) support functions
 
 	=== 4 Host Program support
 	   --- 4.1 Simple Host Program
@@ -38,7 +39,6 @@ This document describes the Linux kernel Makefiles.
 	   --- 6.6 Commands useful for building a boot image
 	   --- 6.7 Custom kbuild commands
 	   --- 6.8 Preprocessing linker scripts
-	   --- 6.9 $(CC) support functions
 
 	=== 7 Kbuild Variables
 	=== 8 Makefile language
@@ -385,6 +385,102 @@ more details, with real examples.
 	to prerequisites are referenced with $(src) (because they are not
 	generated files).
 
+--- 3.11 $(CC) support functions
+
+	The kernel may be build with several different versions of
+	$(CC), each supporting a unique set of features and options.
+	kbuild provide basic support to check for valid options for $(CC).
+	$(CC) is useally the gcc compiler, but other alternatives are
+	available.
+
+    as-option
+    	as-option is used to check if $(CC) when used to compile
+	assembler (*.S) files supports the given option. An optional
+	second option may be specified if first option are not supported.
+
+	Example:
+		#arch/sh/Makefile
+		cflags-y += $(call as-option,-Wa$(comma)-isa=$(isa-y),)
+
+	In the above example cflags-y will be assinged the the option
+	-Wa$(comma)-isa=$(isa-y) if it is supported by $(CC).
+	The second argument is optional, and if supplied will be used
+	if first argument is not supported.
+
+    cc-option
+	cc-option is used to check if $(CC) support a given option, and not
+	supported to use an optional second option.
+
+	Example:
+		#arch/i386/Makefile
+		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
+
+	In the above example cflags-y will be assigned the option
+	-march=pentium-mmx if supported by $(CC), otherwise -march-i586.
+	The second argument to cc-option is optional, and if omitted
+	cflags-y will be assigned no value if first option is not supported.
+
+   cc-option-yn
+   	cc-option-yn is used to check if gcc supports a given option
+	and return 'y' if supported, otherwise 'n'.
+
+	Example:
+		#arch/ppc/Makefile
+		biarch := $(call cc-option-yn, -m32)
+		aflags-$(biarch) += -a32
+		cflags-$(biarch) += -m32
+	
+	In the above example $(biarch) is set to y if $(CC) supports the -m32
+	option. When $(biarch) equals to y the expanded variables $(aflags-y)
+	and $(cflags-y) will be assigned the values -a32 and -m32.
+
+    cc-option-align
+	gcc version >= 3.0 shifted type of options used to speify
+	alignment of functions, loops etc. $(cc-option-align) whrn used
+	as prefix to the align options will select the right prefix:
+	gcc < 3.00
+		cc-option-align = -malign
+	gcc >= 3.00
+		cc-option-align = -falign
+	
+	Example:
+		CFLAGS += $(cc-option-align)-functions=4
+
+	In the above example the option -falign-functions=4 is used for
+	gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
+	
+    cc-version
+	cc-version return a numerical version of the $(CC) compiler version.
+	The format is <major><minor> where both are two digits. So for example
+	gcc 3.41 would return 0341.
+	cc-version is useful when a specific $(CC) version is faulty in one
+	area, for example the -mregparm=3 were broken in some gcc version
+	even though the option was accepted by gcc.
+
+	Example:
+		#arch/i386/Makefile
+		cflags-y += $(shell \
+		if [ $(call cc-version) -ge 0300 ] ; then \
+			echo "-mregparm=3"; fi ;)
+
+	In the above example -mregparm=3 is only used for gcc version greater
+	than or equal to gcc 3.0.
+
+    cc-ifversion
+	cc-ifversion test the version of $(CC) and equals last argument if
+	version expression is true.
+
+	Example:
+		#fs/reiserfs/Makefile
+		EXTRA_CFLAGS := $(call cc-ifversion, -lt, 0402, -O1)
+
+	In this example EXTRA_CFLAGS will be assigned the value -O1 if the
+	$(CC) version is less than 4.2.
+	cc-ifversion takes all the shell operators: 
+	-eq, -ne, -lt, -le, -gt, and -ge
+	The third parameter may be a text as in this example, but it may also
+	be an expanded variable or a macro.
+
 
 === 4 Host Program support
 
@@ -973,74 +1069,6 @@ When kbuild executes the following steps are followed (roughly):
 	architecture specific files.
 
 
---- 6.9 $(CC) support functions
-
-	The kernel may be build with several different versions of
-	$(CC), each supporting a unique set of features and options.
-	kbuild provide basic support to check for valid options for $(CC).
-	$(CC) is useally the gcc compiler, but other alternatives are
-	available.
-
-    cc-option
-	cc-option is used to check if $(CC) support a given option, and not
-	supported to use an optional second option.
-
-	Example:
-		#arch/i386/Makefile
-		cflags-y += $(call cc-option,-march=pentium-mmx,-march=i586)
-
-	In the above example cflags-y will be assigned the option
-	-march=pentium-mmx if supported by $(CC), otherwise -march-i586.
-	The second argument to cc-option is optional, and if omitted
-	cflags-y will be assigned no value if first option is not supported.
-
-   cc-option-yn
-   	cc-option-yn is used to check if gcc supports a given option
-	and return 'y' if supported, otherwise 'n'.
-
-	Example:
-		#arch/ppc/Makefile
-		biarch := $(call cc-option-yn, -m32)
-		aflags-$(biarch) += -a32
-		cflags-$(biarch) += -m32
-	
-	In the above example $(biarch) is set to y if $(CC) supports the -m32
-	option. When $(biarch) equals to y the expanded variables $(aflags-y)
-	and $(cflags-y) will be assigned the values -a32 and -m32.
-
-    cc-option-align
-	gcc version >= 3.0 shifted type of options used to speify
-	alignment of functions, loops etc. $(cc-option-align) whrn used
-	as prefix to the align options will select the right prefix:
-	gcc < 3.00
-		cc-option-align = -malign
-	gcc >= 3.00
-		cc-option-align = -falign
-	
-	Example:
-		CFLAGS += $(cc-option-align)-functions=4
-
-	In the above example the option -falign-functions=4 is used for
-	gcc >= 3.00. For gcc < 3.00 -malign-functions=4 is used.
-	
-    cc-version
-	cc-version return a numerical version of the $(CC) compiler version.
-	The format is <major><minor> where both are two digits. So for example
-	gcc 3.41 would return 0341.
-	cc-version is useful when a specific $(CC) version is faulty in one
-	area, for example the -mregparm=3 were broken in some gcc version
-	even though the option was accepted by gcc.
-
-	Example:
-		#arch/i386/Makefile
-		cflags-y += $(shell \
-		if [ $(call cc-version) -ge 0300 ] ; then \
-			echo "-mregparm=3"; fi ;)
-
-	In the above example -mregparm=3 is only used for gcc version greater
-	than or equal to gcc 3.0.
-	
-
 === 7 Kbuild Variables
 
 The top Makefile exports the following variables: