Rewrite test_libs.sh

This rewritten version improves upon the previous one in the following
ways:

- Automatically determines whether to exclude AVX and SSE cases from
  what it builds and tests. It queries the host computer about the
  features it supports in order to make this determination.
- Doesn't uses a hardwired list of cases to build and test. Instead,
  it uses Bazel filters based on tags.
- Adds a `--help` option.

Author: mhucka

dev_tools/test_libs.sh

@@ -20,27 +20,64 @@ Run the programs in tests/, and on Linux, also build the programs in apps/.
 
 If the first option on the command line is -h, --help, or help, this help text
 will be printed and the program will exit. Any other options on the command
-line are passed directly to Bazel.
-
-Note: the MacOS VMs in GitHub runners may run on different-capability CPUS, so
-all AVX versions of programs in tests/ are automatically excluded."
+line are passed directly to Bazel."
 
 # Exit early if the user requested help.
 if [[ "$1" == "-h" || "$1" == "--help" || "$1" == "help" ]]; then
     echo "$usage"
     exit 0
 fi
 
-declare filter_avx=""
-if [[ "$OSTYPE" == "darwin"* ]]; then
-    filter_avx="--test_tag_filters=-avx"
+# Unless we can tell this system supports AVX, we skip those tests.
+declare avx=false
+declare sse=false
+shopt -s nocasematch
+# Note: can't use Bash's $OSTYPE here b/c the value is "linux-gnu" on Win 10.
+case "$(uname -s)" in
+    darwin*)
+        features=$(sysctl machdep.cpu.features)
+        [[ "$features" == *"avx2"* ]] && avx=true
+        [[ "$features" == *"sse"* ]] && sse=true
+        ;;
+
+    linux*)
+        flags=$(grep -qi flags /proc/cpuinfo)
+        [[ "$flags" == *"avx2"* ]] && avx=true
+        [[ "$flags" == *"sse"* ]] && sse=true
+        ;;
+
+    windows*|cygwin*|mingw32*|msys*|mingw*)
+        if wmic cpu get Caption /value | grep -qi "avx2"; then
+            avx=true
+        elif wmic cpu get InstructionSet /value | grep -qi "avx2"; then
+            avx=true
+        fi
+        if wmic cpu get Caption /value | grep -qi "sse"; then
+            sse=true
+        elif wmic cpu get InstructionSet /value | grep -qi "sse"; then
+            sse=true
+        fi
+        ;;
+esac
+
+declare build_filters=""
+declare test_filters=""
+if ! $avx; then
+    build_filters="--build_tag_filters=-avx"
+    test_filters="--test_tag_filters=-avx"
+fi
+if ! $sse; then
+    build_filters+=",-sse"
+    test_filters+=",-sse"
 fi
 
 # Apps are sample programs and are only meant to run on Linux.
+# shellcheck disable=SC2086
 if [[ "$OSTYPE" == "linux-gnu"* ]]; then
-    bazel build --config=sse $filter_avx "$@" apps:all
-    bazel build $filter_avx "$@" apps:all
+    bazel build $build_filters --config=sse "$@" apps:all
+    bazel build $build_filters "$@" apps:all
 fi
 
 # Run all basic tests. This should work on all platforms.
-bazel test $filter_avx "$@" tests:all
+# shellcheck disable=SC2086
+bazel test $build_filters $test_filters "$@" tests:all