utils.py: add parallel make helpers

The code to extract the integer number of parallel build threads and
construct a new argument from them has started to be copied in multiple
locations, so create two new helper utilities to aid recipes.

The first helper (parallel_make()) extracts the integer number of
parallel build threads from PARALLEL_MAKE. The second
(parallel_make_argument()) does the same and then puts the result back
into a format string, optionally clamping it to some maximum value.

Additionally, rework the oe-core recipes that were manually doing this
to use the new helper utilities.

(From OE-Core rev: ccd1142d22b31ed85d8823b1bc9e11ccfd72b61f)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/go.bbclass

@@ -1,23 +1,6 @@
 inherit goarch ptest
 
-def get_go_parallel_make(d):
+GO_PARALLEL_BUILD ?= "${@oe.utils.parallel_make_argument(d, '-p %d')}"
-    pm = (d.getVar('PARALLEL_MAKE') or '').split()
-    # look for '-j' and throw other options (e.g. '-l') away
-    # because they might have a different meaning in golang
-    while pm:
-        opt = pm.pop(0)
-        if opt == '-j':
-            v = pm.pop(0)
-        elif opt.startswith('-j'):
-            v = opt[2:].strip()
-        else:
-            continue
-
-        return '-p %d' % int(v)
-
-    return ""
-
-GO_PARALLEL_BUILD ?= "${@get_go_parallel_make(d)}"
 
 GOROOT_class-native = "${STAGING_LIBDIR_NATIVE}/go"
 GOROOT_class-nativesdk = "${STAGING_DIR_TARGET}${libdir}/go"

meta/classes/waf.bbclass

@@ -3,28 +3,6 @@ DISABLE_STATIC = ""
 
 EXTRA_OECONF_append = " ${PACKAGECONFIG_CONFARGS}"
 
-def get_waf_parallel_make(d):
-    pm = d.getVar('PARALLEL_MAKE')
-    if pm:
-        # look for '-j' and throw other options (e.g. '-l') away
-        # because they might have different meaning in bjam
-        pm = pm.split()
-        while pm:
-            v = None
-            opt = pm.pop(0)
-            if opt == '-j':
-                v = pm.pop(0)
-            elif opt.startswith('-j'):
-                v = opt[2:].strip()
-            else:
-                v = None
-
-            if v:
-                v = min(64, int(v))
-                return '-j' + str(v)
-
-    return ""
-
 python waf_preconfigure() {
     import subprocess
     from distutils.version import StrictVersion
@@ -47,7 +25,7 @@ waf_do_configure() {
 
 do_compile[progress] = "outof:^\[\s*(\d+)/\s*(\d+)\]\s+"
 waf_do_compile()  {
-	${S}/waf build ${@get_waf_parallel_make(d)}
+	${S}/waf build ${@oe.utils.parallel_make_argument(d, '-j%d', limit=64)}
 }
 
 waf_do_install() {

meta/lib/oe/utils.py

@@ -156,6 +156,49 @@ def any_distro_features(d, features, truevalue="1", falsevalue=""):
     """
     return bb.utils.contains_any("DISTRO_FEATURES", features, truevalue, falsevalue, d)
 
+def parallel_make(d):
+    """
+    Return the integer value for the number of parallel threads to use when
+    building, scraped out of PARALLEL_MAKE. If no parallelization option is
+    found, returns None
+
+    e.g. if PARALLEL_MAKE = "-j 10", this will return 10 as an integer.
+    """
+    pm = (d.getVar('PARALLEL_MAKE') or '').split()
+    # look for '-j' and throw other options (e.g. '-l') away
+    while pm:
+        opt = pm.pop(0)
+        if opt == '-j':
+            v = pm.pop(0)
+        elif opt.startswith('-j'):
+            v = opt[2:].strip()
+        else:
+            continue
+
+        return int(v)
+
+    return None
+
+def parallel_make_argument(d, fmt, limit=None):
+    """
+    Helper utility to construct a parallel make argument from the number of
+    parallel threads specified in PARALLEL_MAKE.
+
+    Returns the input format string `fmt` where a single '%d' will be expanded
+    with the number of parallel threads to use. If `limit` is specified, the
+    number of parallel threads will be no larger than it. If no parallelization
+    option is found in PARALLEL_MAKE, returns an empty string
+
+    e.g. if PARALLEL_MAKE = "-j 10", parallel_make_argument(d, "-n %d") will return
+    "-n 10"
+    """
+    v = parallel_make(d)
+    if v:
+        if limit:
+            v = max(limit, v)
+        return fmt % v
+    return ''
+
 def packages_filter_out_system(d):
     """
     Return a list of packages from PACKAGES with the "system" packages such as

meta/recipes-core/ovmf/ovmf_git.bb

@@ -151,7 +151,7 @@ do_compile_class-native() {
 
 do_compile_class-target() {
     export LFLAGS="${LDFLAGS}"
-    PARALLEL_JOBS="${@ '${PARALLEL_MAKE}'.replace('-j', '-n ')}"
+    PARALLEL_JOBS="${@oe.utils.parallel_make_argument(d, '-n %d')}"
     OVMF_ARCH="X64"
     if [ "${TARGET_ARCH}" != "x86_64" ] ; then
         OVMF_ARCH="IA32"

meta/recipes-support/boost/boost.inc

@@ -135,29 +135,7 @@ BJAM_TOOLS   = "--ignore-site-config \
 
 # use PARALLEL_MAKE to speed up the build, but limit it by -j 64, greater parallelism causes bjam to segfault or to ignore -j
 # https://svn.boost.org/trac/boost/ticket/7634
-def get_boost_parallel_make(d):
+BOOST_PARALLEL_MAKE = "${@oe.utils.parallel_make_argument(d, '-j%d', limit=64)}"
-    pm = d.getVar('PARALLEL_MAKE')
-    if pm:
-        # look for '-j' and throw other options (e.g. '-l') away
-        # because they might have different meaning in bjam
-        pm = pm.split()
-        while pm:
-            v = None
-            opt = pm.pop(0)
-            if opt == '-j':
-                v = pm.pop(0)
-            elif opt.startswith('-j'):
-                v = opt[2:].strip()
-            else:
-                v = None
-
-            if v:
-                v = min(64, int(v))
-                return '-j' + str(v)
-
-    return ""
-
-BOOST_PARALLEL_MAKE = "${@get_boost_parallel_make(d)}"
 BJAM_OPTS    = '${BOOST_PARALLEL_MAKE} -d+2 -q \
 		${BJAM_TOOLS} \
 		-sBOOST_BUILD_USER_CONFIG=${WORKDIR}/user-config.jam \