round-robin.sh: Add no_build_regression_p helper

... by moving code from tcwg_gnu-build.sh.  This helper will also
be used in upcoming improvements to tcwg_bmk-build.sh.

Change-Id: I298cefc6d65d13461e3de53ef542b4a804042fad

1 files changed, 29 insertions, 0 deletions

diff --git a/round-robin.sh b/round-robin.sh
index f886c73a..caf9c3e2 100644
--- a/round-robin.sh
+++ b/round-robin.sh
@@ -432,6 +432,35 @@ EOF
     )
 }
 
+# Exit with code 0 if no regression compared to base-artifacts/results.
+no_build_regression_p ()
+{
+    (
+    set -euf -o pipefail
+
+    local ref_artifacts=$1
+    local new_artifacts=$2
+
+    # The following check tests for an empty branch, and we return 0 if results
+    # are not present, since that's an inherently better state. If base-artifacts
+    # were not existing, then it would fail in reset_artifacts() stage.
+
+    if ! [ -f $ref_artifacts/results ]; then
+	return 0
+    fi
+
+    local build_result_ref build_result_new
+    build_result_ref=$(tail -n1 $ref_artifacts/results)
+    build_result_new=$(tail -n1 $new_artifacts/results)
+
+    if [ $build_result_new -lt $build_result_ref ]; then
+	return 1
+    elif [ $build_result_new -gt $build_result_ref ]; then
+	return 0
+    fi
+    )
+}
+
 # Check if current build regressed compared to the baseline
 # (unless ${rr[update_baseline]} is set to "reset").
 check_regression ()