Optimize ebuild.sh to cache preprocessing output.

Right now ebuild.sh runs preprocessing steps multiple times during the
same build. It processes the same environment and produces the same
output every time. This slows down the build unnecessarily.

This optimization cuts build time for 50 binary packages with 16 jobs
from 3m22 to 2m33 (33%).

Change-Id: I72ac84cce2eb60d17736cc5f5343d4a858ec86f4

Review URL: http://codereview.chromium.org/6733008

diff --git a/bin/ebuild.sh b/bin/ebuild.sh
index 59bf46e918ada69bc8ab72568eeb02b68b65a2c1..c79d4c3d03ded25b70496a2b26ed66f89161545a 100755 (executable)
--- a/bin/ebuild.sh
+++ b/bin/ebuild.sh
@@ -1826,14 +1826,14 @@ filter_readonly_variables() {
 # interfering with the current environment. This is useful when an existing
 # environment needs to be loaded from a binary or installed package.
 preprocess_ebuild_env() {
-       local _portage_filter_opts=""
-       if [ -f "${T}/environment.raw" ] ; then
-               # This is a signal from the python side, indicating that the
-               # environment may contain stale SANDBOX_{DENY,PREDICT,READ,WRITE}
-               # and FEATURES variables that should be filtered out. Between
-               # phases, these variables are normally preserved.
-               _portage_filter_opts+=" --filter-features --filter-locale --filter-path --filter-sandbox"
-       fi
+       local _portage_filter_opts="--filter-features --filter-locale --filter-path --filter-sandbox"
+
+       # If environment.raw is present, this is a signal from the python side,
+       # indicating that the environment may contain stale FEATURES and
+       # SANDBOX_{DENY,PREDICT,READ,WRITE} variables that should be filtered out.
+       # Otherwise, we don't need to filter the environment.
+       [ -f "${T}/environment.raw" ] || return 0
+
        filter_readonly_variables $_portage_filter_opts < "${T}"/environment \
                >> "$T/environment.filtered" || return $?
        unset _portage_filter_opts