import-layers/yocto-poky/meta/classes/icecc.bbclass - openbmc/openbmc - Gitiles

 # IceCream distributed compiling support
 #
 # Stages directories with symlinks from gcc/g++ to icecc, for both
 # native and cross compilers. Depending on each configure or compile,
 # the directories are added at the head of the PATH list and ICECC_CXX
 # and ICEC_CC are set.
 #
 # For the cross compiler, creates a tar.gz of our toolchain and sets
 # ICECC_VERSION accordingly.
 #
 # The class now handles all 3 different compile 'stages' (i.e native ,cross-kernel and target) creating the
 # necessary environment tar.gz file to be used by the remote machines.
 # It also supports meta-toolchain generation
 #
 # If ICECC_PATH is not set in local.conf then the class will try to locate it using 'bb.utils.which'
 # but nothing is sure ;)
 #
 # If ICECC_ENV_EXEC is set in local.conf, then it should point to the icecc-create-env script provided by the user
 # or the default one provided by icecc-create-env.bb will be used
 # (NOTE that this is a modified version of the script need it and *not the one that comes with icecc*
 #
 # User can specify if specific packages or packages belonging to class should not use icecc to distribute
 # compile jobs to remote machines, but handled locally, by defining ICECC_USER_CLASS_BL and ICECC_USER_PACKAGE_BL
 # with the appropriate values in local.conf. In addition the user can force to enable icecc for packages
 # which set an empty PARALLEL_MAKE variable by defining ICECC_USER_PACKAGE_WL.
 #
 #########################################################################################
 #Error checking is kept to minimum so double check any parameters you pass to the class
 ###########################################################################################

 BB_HASHBASE_WHITELIST += "ICECC_PARALLEL_MAKE ICECC_DISABLED ICECC_USER_PACKAGE_BL ICECC_USER_CLASS_BL ICECC_USER_PACKAGE_WL ICECC_PATH ICECC_ENV_EXEC"

 ICECC_ENV_EXEC ?= "${STAGING_BINDIR_NATIVE}/icecc-create-env"

 def icecc_dep_prepend(d):
     # INHIBIT_DEFAULT_DEPS doesn't apply to the patch command.  Whether or  not
     # we need that built is the responsibility of the patch function / class, not
     # the application.
     if not d.getVar('INHIBIT_DEFAULT_DEPS', False):
         return "icecc-create-env-native"
     return ""

 DEPENDS_prepend += "${@icecc_dep_prepend(d)} "

 def get_cross_kernel_cc(bb,d):
     kernel_cc = d.getVar('KERNEL_CC', False)

     # evaluate the expression by the shell if necessary
     if '`' in kernel_cc or '$(' in kernel_cc:
         kernel_cc = os.popen("echo %s" % kernel_cc).read()[:-1]

     kernel_cc = d.expand(kernel_cc)
     kernel_cc = kernel_cc.replace('ccache', '').strip()
     kernel_cc = kernel_cc.split(' ')[0]
     kernel_cc = kernel_cc.strip()
     return kernel_cc

 def get_icecc(d):
     return d.getVar('ICECC_PATH', False) or bb.utils.which(os.getenv("PATH"), "icecc")

 def create_path(compilers, bb, d):
     """
     Create Symlinks for the icecc in the staging directory
     """
     staging = os.path.join(d.expand('${STAGING_BINDIR}'), "ice")
     if icecc_is_kernel(bb, d):
         staging += "-kernel"

     #check if the icecc path is set by the user
     icecc = get_icecc(d)

     # Create the dir if necessary
     try:
         os.stat(staging)
     except:
         try:
             os.makedirs(staging)
         except:
             pass

     for compiler in compilers:
         gcc_path = os.path.join(staging, compiler)
         try:
             os.stat(gcc_path)
         except:
             try:
                 os.symlink(icecc, gcc_path)
             except:
                 pass

     return staging

 def use_icecc(bb,d):
     if d.getVar('ICECC_DISABLED', False) == "1":
         # don't even try it, when explicitly disabled
         return "no"

     # allarch recipes don't use compiler
     if icecc_is_allarch(bb, d):
         return "no"

     pn = d.getVar('PN', True)

     system_class_blacklist = []
     user_class_blacklist = (d.getVar('ICECC_USER_CLASS_BL', False) or "none").split()
     package_class_blacklist = system_class_blacklist + user_class_blacklist

     for black in package_class_blacklist:
         if bb.data.inherits_class(black, d):
             bb.debug(1, "%s: class %s found in blacklist, disable icecc" % (pn, black))
             return "no"

     # "system" recipe blacklist contains a list of packages that can not distribute compile tasks
     # for one reason or the other
     # this is the old list (which doesn't seem to be valid anymore, because I was able to build
     # all these with icecc enabled)
     # system_package_blacklist = [ "uclibc", "glibc", "gcc", "bind", "u-boot", "dhcp-forwarder", "enchant", "connman", "orbit2" ]
     # when adding new entry, please document why (how it failed) so that we can re-evaluate it later
     # e.g. when there is new version
     # building libgcc-initial with icecc fails with CPP sanity check error if host sysroot contains cross gcc built for another target tune/variant
     system_package_blacklist = ["libgcc-initial"]
     user_package_blacklist = (d.getVar('ICECC_USER_PACKAGE_BL', False) or "").split()
     user_package_whitelist = (d.getVar('ICECC_USER_PACKAGE_WL', False) or "").split()
     package_blacklist = system_package_blacklist + user_package_blacklist

     if pn in package_blacklist:
         bb.debug(1, "%s: found in blacklist, disable icecc" % pn)
         return "no"

     if pn in user_package_whitelist:
         bb.debug(1, "%s: found in whitelist, enable icecc" % pn)
         return "yes"

     if d.getVar('PARALLEL_MAKE', False) == "":
         bb.debug(1, "%s: has empty PARALLEL_MAKE, disable icecc" % pn)
         return "no"

     return "yes"

 def icecc_is_allarch(bb, d):
     return d.getVar("PACKAGE_ARCH", True) == "all" or bb.data.inherits_class('allarch', d)

 def icecc_is_kernel(bb, d):
     return \
         bb.data.inherits_class("kernel", d);

 def icecc_is_native(bb, d):
     return \
         bb.data.inherits_class("cross", d) or \
         bb.data.inherits_class("native", d);

 # Don't pollute allarch signatures with TARGET_FPU
 icecc_version[vardepsexclude] += "TARGET_FPU"
 def icecc_version(bb, d):
     if use_icecc(bb, d) == "no":
         return ""

     parallel = d.getVar('ICECC_PARALLEL_MAKE', False) or ""
     if not d.getVar('PARALLEL_MAKE', False) == "" and parallel:
         d.setVar("PARALLEL_MAKE", parallel)

     if icecc_is_native(bb, d):
         archive_name = "local-host-env"
     elif d.expand('${HOST_PREFIX}') == "":
         bb.fatal(d.expand("${PN}"), " NULL prefix")
     else:
         prefix = d.expand('${HOST_PREFIX}' )
         distro = d.expand('${DISTRO}')
         target_sys = d.expand('${TARGET_SYS}')
         float = d.getVar('TARGET_FPU', False) or "hard"
         archive_name = prefix + distro + "-"        + target_sys + "-" + float
         if icecc_is_kernel(bb, d):
             archive_name += "-kernel"

     import socket
     ice_dir = d.expand('${STAGING_DIR_NATIVE}${prefix_native}')
     tar_file = os.path.join(ice_dir, 'ice', archive_name + "-@VERSION@-" + socket.gethostname() + '.tar.gz')

     return tar_file

 def icecc_path(bb,d):
     if use_icecc(bb, d) == "no":
         # don't create unnecessary directories when icecc is disabled
         return

     if icecc_is_kernel(bb, d):
         return create_path( [get_cross_kernel_cc(bb,d), ], bb, d)

     else:
         prefix = d.expand('${HOST_PREFIX}')
         return create_path( [prefix+"gcc", prefix+"g++"], bb, d)

 def icecc_get_external_tool(bb, d, tool):
     external_toolchain_bindir = d.expand('${EXTERNAL_TOOLCHAIN}${bindir_cross}')
     target_prefix = d.expand('${TARGET_PREFIX}')
     return os.path.join(external_toolchain_bindir, '%s%s' % (target_prefix, tool))

 # Don't pollute native signatures with target TUNE_PKGARCH through STAGING_BINDIR_TOOLCHAIN
 icecc_get_tool[vardepsexclude] += "STAGING_BINDIR_TOOLCHAIN"
 def icecc_get_tool(bb, d, tool):
     if icecc_is_native(bb, d):
         return bb.utils.which(os.getenv("PATH"), tool)
     elif icecc_is_kernel(bb, d):
         return bb.utils.which(os.getenv("PATH"), get_cross_kernel_cc(bb, d))
     else:
         ice_dir = d.expand('${STAGING_BINDIR_TOOLCHAIN}')
         target_sys = d.expand('${TARGET_SYS}')
         tool_bin = os.path.join(ice_dir, "%s-%s" % (target_sys, tool))
         if os.path.isfile(tool_bin):
             return tool_bin
         else:
             external_tool_bin = icecc_get_external_tool(bb, d, tool)
             if os.path.isfile(external_tool_bin):
                 return external_tool_bin
             else:
                 return ""

 def icecc_get_and_check_tool(bb, d, tool):
     # Check that g++ or gcc is not a symbolic link to icecc binary in
     # PATH or icecc-create-env script will silently create an invalid
     # compiler environment package.
     t = icecc_get_tool(bb, d, tool)
     if t and os.popen("readlink -f %s" % t).read()[:-1] == get_icecc(d):
         bb.error("%s is a symlink to %s in PATH and this prevents icecc from working" % (t, get_icecc(d)))
         return ""
     else:
         return t

 wait_for_file() {
     local TIME_ELAPSED=0
     local FILE_TO_TEST=$1
     local TIMEOUT=$2
     until [ -f "$FILE_TO_TEST" ]
     do
         TIME_ELAPSED=`expr $TIME_ELAPSED + 1`
         if [ $TIME_ELAPSED -gt $TIMEOUT ]
         then
             return 1
         fi
         sleep 1
     done
 }

 def set_icecc_env():
     # dummy python version of set_icecc_env
     return

 set_icecc_env() {
     if [ "${@use_icecc(bb, d)}" = "no" ]
     then
         return
     fi
     ICECC_VERSION="${@icecc_version(bb, d)}"
     if [ "x${ICECC_VERSION}" = "x" ]
     then
         bbwarn "Cannot use icecc: could not get ICECC_VERSION"
         return
     fi

     ICE_PATH="${@icecc_path(bb, d)}"
     if [ "x${ICE_PATH}" = "x" ]
     then
         bbwarn "Cannot use icecc: could not get ICE_PATH"
         return
     fi

     ICECC_CC="${@icecc_get_and_check_tool(bb, d, "gcc")}"
     ICECC_CXX="${@icecc_get_and_check_tool(bb, d, "g++")}"
     # cannot use icecc_get_and_check_tool here because it assumes as without target_sys prefix
     ICECC_WHICH_AS="${@bb.utils.which(os.getenv('PATH'), 'as')}"
     if [ ! -x "${ICECC_CC}" -o ! -x "${ICECC_CXX}" ]
     then
         bbwarn "Cannot use icecc: could not get ICECC_CC or ICECC_CXX"
         return
     fi

     ICE_VERSION=`$ICECC_CC -dumpversion`
     ICECC_VERSION=`echo ${ICECC_VERSION} | sed -e "s/@VERSION@/$ICE_VERSION/g"`
     if [ ! -x "${ICECC_ENV_EXEC}" ]
     then
         bbwarn "Cannot use icecc: invalid ICECC_ENV_EXEC"
         return
     fi

     ICECC_AS="`${ICECC_CC} -print-prog-name=as`"
     # for target recipes should return something like:
     # /OE/tmp-eglibc/sysroots/x86_64-linux/usr/libexec/arm920tt-oe-linux-gnueabi/gcc/arm-oe-linux-gnueabi/4.8.2/as
     # and just "as" for native, if it returns "as" in current directory (for whatever reason) use "as" from PATH
     if [ "`dirname "${ICECC_AS}"`" = "." ]
     then
         ICECC_AS="${ICECC_WHICH_AS}"
     fi

     if [ ! -f "${ICECC_VERSION}.done" ]
     then
         mkdir -p "`dirname "${ICECC_VERSION}"`"

         # the ICECC_VERSION generation step must be locked by a mutex
         # in order to prevent race conditions
         if flock -n "${ICECC_VERSION}.lock" \
             ${ICECC_ENV_EXEC} "${ICECC_CC}" "${ICECC_CXX}" "${ICECC_AS}" "${ICECC_VERSION}"
         then
             touch "${ICECC_VERSION}.done"
         elif [ ! wait_for_file "${ICECC_VERSION}.done" 30 ]
         then
             # locking failed so wait for ${ICECC_VERSION}.done to appear
             bbwarn "Timeout waiting for ${ICECC_VERSION}.done"
             return
         fi
     fi

     export ICECC_VERSION ICECC_CC ICECC_CXX
     export PATH="$ICE_PATH:$PATH"
     export CCACHE_PATH="$PATH"

     bbnote "Using icecc"
 }

 do_configure_prepend() {
     set_icecc_env
 }

 do_compile_prepend() {
     set_icecc_env
 }

 do_compile_kernelmodules_prepend() {
     set_icecc_env
 }

 do_install_prepend() {
     set_icecc_env
 }
	# IceCream distributed compiling support
	#
	# Stages directories with symlinks from gcc/g++ to icecc, for both
	# native and cross compilers. Depending on each configure or compile,
	# the directories are added at the head of the PATH list and ICECC_CXX
	# and ICEC_CC are set.
	#
	# For the cross compiler, creates a tar.gz of our toolchain and sets
	# ICECC_VERSION accordingly.
	#
	# The class now handles all 3 different compile 'stages' (i.e native ,cross-kernel and target) creating the
	# necessary environment tar.gz file to be used by the remote machines.
	# It also supports meta-toolchain generation
	#
	# If ICECC_PATH is not set in local.conf then the class will try to locate it using 'bb.utils.which'
	# but nothing is sure ;)
	#
	# If ICECC_ENV_EXEC is set in local.conf, then it should point to the icecc-create-env script provided by the user
	# or the default one provided by icecc-create-env.bb will be used
	# (NOTE that this is a modified version of the script need it and not the one that comes with icecc
	#
	# User can specify if specific packages or packages belonging to class should not use icecc to distribute
	# compile jobs to remote machines, but handled locally, by defining ICECC_USER_CLASS_BL and ICECC_USER_PACKAGE_BL
	# with the appropriate values in local.conf. In addition the user can force to enable icecc for packages
	# which set an empty PARALLEL_MAKE variable by defining ICECC_USER_PACKAGE_WL.
	#
	#########################################################################################
	#Error checking is kept to minimum so double check any parameters you pass to the class
	###########################################################################################

	BB_HASHBASE_WHITELIST += "ICECC_PARALLEL_MAKE ICECC_DISABLED ICECC_USER_PACKAGE_BL ICECC_USER_CLASS_BL ICECC_USER_PACKAGE_WL ICECC_PATH ICECC_ENV_EXEC"

	ICECC_ENV_EXEC ?= "${STAGING_BINDIR_NATIVE}/icecc-create-env"

	def icecc_dep_prepend(d):
	# INHIBIT_DEFAULT_DEPS doesn't apply to the patch command. Whether or not
	# we need that built is the responsibility of the patch function / class, not
	# the application.
	if not d.getVar('INHIBIT_DEFAULT_DEPS', False):
	return "icecc-create-env-native"
	return ""

	DEPENDS_prepend += "${@icecc_dep_prepend(d)} "

	def get_cross_kernel_cc(bb,d):
	kernel_cc = d.getVar('KERNEL_CC', False)

	# evaluate the expression by the shell if necessary
	if '`' in kernel_cc or '$(' in kernel_cc:
	kernel_cc = os.popen("echo %s" % kernel_cc).read()[:-1]

	kernel_cc = d.expand(kernel_cc)
	kernel_cc = kernel_cc.replace('ccache', '').strip()
	kernel_cc = kernel_cc.split(' ')[0]
	kernel_cc = kernel_cc.strip()
	return kernel_cc

	def get_icecc(d):
	return d.getVar('ICECC_PATH', False) or bb.utils.which(os.getenv("PATH"), "icecc")

	def create_path(compilers, bb, d):
	"""
	Create Symlinks for the icecc in the staging directory
	"""
	staging = os.path.join(d.expand('${STAGING_BINDIR}'), "ice")
	if icecc_is_kernel(bb, d):
	staging += "-kernel"

	#check if the icecc path is set by the user
	icecc = get_icecc(d)

	# Create the dir if necessary
	try:
	os.stat(staging)
	except:
	try:
	os.makedirs(staging)
	except:
	pass

	for compiler in compilers:
	gcc_path = os.path.join(staging, compiler)
	try:
	os.stat(gcc_path)
	except:
	try:
	os.symlink(icecc, gcc_path)
	except:
	pass

	return staging

	def use_icecc(bb,d):
	if d.getVar('ICECC_DISABLED', False) == "1":
	# don't even try it, when explicitly disabled
	return "no"

	# allarch recipes don't use compiler
	if icecc_is_allarch(bb, d):
	return "no"

	pn = d.getVar('PN', True)

	system_class_blacklist = []
	user_class_blacklist = (d.getVar('ICECC_USER_CLASS_BL', False) or "none").split()
	package_class_blacklist = system_class_blacklist + user_class_blacklist

	for black in package_class_blacklist:
	if bb.data.inherits_class(black, d):
	bb.debug(1, "%s: class %s found in blacklist, disable icecc" % (pn, black))
	return "no"

	# "system" recipe blacklist contains a list of packages that can not distribute compile tasks
	# for one reason or the other
	# this is the old list (which doesn't seem to be valid anymore, because I was able to build
	# all these with icecc enabled)
	# system_package_blacklist = [ "uclibc", "glibc", "gcc", "bind", "u-boot", "dhcp-forwarder", "enchant", "connman", "orbit2" ]
	# when adding new entry, please document why (how it failed) so that we can re-evaluate it later
	# e.g. when there is new version
	# building libgcc-initial with icecc fails with CPP sanity check error if host sysroot contains cross gcc built for another target tune/variant
	system_package_blacklist = ["libgcc-initial"]
	user_package_blacklist = (d.getVar('ICECC_USER_PACKAGE_BL', False) or "").split()
	user_package_whitelist = (d.getVar('ICECC_USER_PACKAGE_WL', False) or "").split()
	package_blacklist = system_package_blacklist + user_package_blacklist

	if pn in package_blacklist:
	bb.debug(1, "%s: found in blacklist, disable icecc" % pn)
	return "no"

	if pn in user_package_whitelist:
	bb.debug(1, "%s: found in whitelist, enable icecc" % pn)
	return "yes"

	if d.getVar('PARALLEL_MAKE', False) == "":
	bb.debug(1, "%s: has empty PARALLEL_MAKE, disable icecc" % pn)
	return "no"

	return "yes"

	def icecc_is_allarch(bb, d):
	return d.getVar("PACKAGE_ARCH", True) == "all" or bb.data.inherits_class('allarch', d)

	def icecc_is_kernel(bb, d):
	return \
	bb.data.inherits_class("kernel", d);

	def icecc_is_native(bb, d):
	return \
	bb.data.inherits_class("cross", d) or \
	bb.data.inherits_class("native", d);

	# Don't pollute allarch signatures with TARGET_FPU
	icecc_version[vardepsexclude] += "TARGET_FPU"
	def icecc_version(bb, d):
	if use_icecc(bb, d) == "no":
	return ""

	parallel = d.getVar('ICECC_PARALLEL_MAKE', False) or ""
	if not d.getVar('PARALLEL_MAKE', False) == "" and parallel:
	d.setVar("PARALLEL_MAKE", parallel)

	if icecc_is_native(bb, d):
	archive_name = "local-host-env"
	elif d.expand('${HOST_PREFIX}') == "":
	bb.fatal(d.expand("${PN}"), " NULL prefix")
	else:
	prefix = d.expand('${HOST_PREFIX}' )
	distro = d.expand('${DISTRO}')
	target_sys = d.expand('${TARGET_SYS}')
	float = d.getVar('TARGET_FPU', False) or "hard"
	archive_name = prefix + distro + "-" + target_sys + "-" + float
	if icecc_is_kernel(bb, d):
	archive_name += "-kernel"

	import socket
	ice_dir = d.expand('${STAGING_DIR_NATIVE}${prefix_native}')
	tar_file = os.path.join(ice_dir, 'ice', archive_name + "-@VERSION@-" + socket.gethostname() + '.tar.gz')

	return tar_file

	def icecc_path(bb,d):
	if use_icecc(bb, d) == "no":
	# don't create unnecessary directories when icecc is disabled
	return

	if icecc_is_kernel(bb, d):
	return create_path( [get_cross_kernel_cc(bb,d), ], bb, d)

	else:
	prefix = d.expand('${HOST_PREFIX}')
	return create_path( [prefix+"gcc", prefix+"g++"], bb, d)

	def icecc_get_external_tool(bb, d, tool):
	external_toolchain_bindir = d.expand('${EXTERNAL_TOOLCHAIN}${bindir_cross}')
	target_prefix = d.expand('${TARGET_PREFIX}')
	return os.path.join(external_toolchain_bindir, '%s%s' % (target_prefix, tool))

	# Don't pollute native signatures with target TUNE_PKGARCH through STAGING_BINDIR_TOOLCHAIN
	icecc_get_tool[vardepsexclude] += "STAGING_BINDIR_TOOLCHAIN"
	def icecc_get_tool(bb, d, tool):
	if icecc_is_native(bb, d):
	return bb.utils.which(os.getenv("PATH"), tool)
	elif icecc_is_kernel(bb, d):
	return bb.utils.which(os.getenv("PATH"), get_cross_kernel_cc(bb, d))
	else:
	ice_dir = d.expand('${STAGING_BINDIR_TOOLCHAIN}')
	target_sys = d.expand('${TARGET_SYS}')
	tool_bin = os.path.join(ice_dir, "%s-%s" % (target_sys, tool))
	if os.path.isfile(tool_bin):
	return tool_bin
	else:
	external_tool_bin = icecc_get_external_tool(bb, d, tool)
	if os.path.isfile(external_tool_bin):
	return external_tool_bin
	else:
	return ""

	def icecc_get_and_check_tool(bb, d, tool):
	# Check that g++ or gcc is not a symbolic link to icecc binary in
	# PATH or icecc-create-env script will silently create an invalid
	# compiler environment package.
	t = icecc_get_tool(bb, d, tool)
	if t and os.popen("readlink -f %s" % t).read()[:-1] == get_icecc(d):
	bb.error("%s is a symlink to %s in PATH and this prevents icecc from working" % (t, get_icecc(d)))
	return ""
	else:
	return t

	wait_for_file() {
	local TIME_ELAPSED=0
	local FILE_TO_TEST=$1
	local TIMEOUT=$2
	until [ -f "$FILE_TO_TEST" ]
	do
	TIME_ELAPSED=`expr $TIME_ELAPSED + 1`
	if [ $TIME_ELAPSED -gt $TIMEOUT ]
	then
	return 1
	fi
	sleep 1
	done
	}

	def set_icecc_env():
	# dummy python version of set_icecc_env
	return

	set_icecc_env() {
	if [ "${@use_icecc(bb, d)}" = "no" ]
	then
	return
	fi
	ICECC_VERSION="${@icecc_version(bb, d)}"
	if [ "x${ICECC_VERSION}" = "x" ]
	then
	bbwarn "Cannot use icecc: could not get ICECC_VERSION"
	return
	fi

	ICE_PATH="${@icecc_path(bb, d)}"
	if [ "x${ICE_PATH}" = "x" ]
	then
	bbwarn "Cannot use icecc: could not get ICE_PATH"
	return
	fi

	ICECC_CC="${@icecc_get_and_check_tool(bb, d, "gcc")}"
	ICECC_CXX="${@icecc_get_and_check_tool(bb, d, "g++")}"
	# cannot use icecc_get_and_check_tool here because it assumes as without target_sys prefix
	ICECC_WHICH_AS="${@bb.utils.which(os.getenv('PATH'), 'as')}"
	if [ ! -x "${ICECC_CC}" -o ! -x "${ICECC_CXX}" ]
	then
	bbwarn "Cannot use icecc: could not get ICECC_CC or ICECC_CXX"
	return
	fi

	ICE_VERSION=`$ICECC_CC -dumpversion`
	ICECC_VERSION=`echo ${ICECC_VERSION} \| sed -e "s/@VERSION@/$ICE_VERSION/g"`
	if [ ! -x "${ICECC_ENV_EXEC}" ]
	then
	bbwarn "Cannot use icecc: invalid ICECC_ENV_EXEC"
	return
	fi

	ICECC_AS="`${ICECC_CC} -print-prog-name=as`"
	# for target recipes should return something like:
	# /OE/tmp-eglibc/sysroots/x86_64-linux/usr/libexec/arm920tt-oe-linux-gnueabi/gcc/arm-oe-linux-gnueabi/4.8.2/as
	# and just "as" for native, if it returns "as" in current directory (for whatever reason) use "as" from PATH
	if [ "`dirname "${ICECC_AS}"`" = "." ]
	then
	ICECC_AS="${ICECC_WHICH_AS}"
	fi

	if [ ! -f "${ICECC_VERSION}.done" ]
	then
	mkdir -p "`dirname "${ICECC_VERSION}"`"

	# the ICECC_VERSION generation step must be locked by a mutex
	# in order to prevent race conditions
	if flock -n "${ICECC_VERSION}.lock" \
	${ICECC_ENV_EXEC} "${ICECC_CC}" "${ICECC_CXX}" "${ICECC_AS}" "${ICECC_VERSION}"
	then
	touch "${ICECC_VERSION}.done"
	elif [ ! wait_for_file "${ICECC_VERSION}.done" 30 ]
	then
	# locking failed so wait for ${ICECC_VERSION}.done to appear
	bbwarn "Timeout waiting for ${ICECC_VERSION}.done"
	return
	fi
	fi

	export ICECC_VERSION ICECC_CC ICECC_CXX
	export PATH="$ICE_PATH:$PATH"
	export CCACHE_PATH="$PATH"

	bbnote "Using icecc"
	}

	do_configure_prepend() {
	set_icecc_env
	}

	do_compile_prepend() {
	set_icecc_env
	}

	do_compile_kernelmodules_prepend() {
	set_icecc_env
	}

	do_install_prepend() {
	set_icecc_env
	}