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>

4 files changed, 136 insertions, 102 deletions

diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt
index 443230b43e09..99d51a5bb0d9 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