testsuite: Add predicate for CPU feature availabilitywip/testsuite-cpu-features

Previously testing code-generation for ISA extensions was nearly impossible
since we had no ability to determine whether the host supports the needed
extension. Here we fix this by introducing a simple /proc/cpuinfo-based
testsuite predicate. We really ought to

2 files changed, 72 insertions, 0 deletions

diff --git a/testsuite/driver/cpu_features.py b/testsuite/driver/cpu_features.py
new file mode 100644
index 0000000000..b9e43470da
--- /dev/null
+++ b/testsuite/driver/cpu_features.py
@@ -0,0 +1,71 @@
+import os
+from testglobals import config
+
+# Feature names generally follow the naming used by Linux's /proc/cpuinfo.
+SUPPORTED_CPU_FEATURES = {
+    # These aren't comprehensive; they are only CPU features that we care about
+
+    # x86:
+    'sse', 'sse2', 'sse3', 'ssse3', 'sse4_1', 'sse4_2',
+    'avx1', 'avx2',
+    'popcnt', 'bmi1', 'bmi2'
+}
+
+cpu_feature_cache = None
+
+def get_cpu_features():
+    if config.os == 'Linux' and os.path.exists('/proc/cpuinfo'):
+        import re
+        f = open('/proc/cpuinfo').read()
+        flags = re.search(r'flags\s*:\s*.*$', f, re.M)
+        if flags is None:
+            print('get_cpu_features: failed to find cpu features')
+            return {}
+        flags = set(flags[0].split())
+        if 'pni' in flags:
+            flags.add('sse3')
+            flags.remove('pni')
+        return flags
+
+    elif config.os == 'Darwin':
+        import subprocess
+        out, err = subprocess.check_output(['sysctl', 'hw'])
+        features = {}
+        def check_feature(darwin_name, our_name=None):
+            if re.find(r'hw\.optional.%s:\s*1' % darwin_name, out):
+                features.add(darwin_name if our_name is None else our_name)
+
+        for feature in SUPPORTED_CPU_FEATURES:
+            check_feature(feature)
+
+        # A few annoying cases
+        check_feature('avx1_0', 'avx1')
+        check_feature('avx2_0', 'avx2')
+        return features
+
+    else:
+        # TODO: Add Windows support
+        print('get_cpu_features: Lacking support for your platform')
+
+    return {}
+
+def have_cpu_feature(feature):
+    """
+    A testsuite predicate for testing the availability of CPU features.
+    """
+    assert feature in SUPPORTED_CPU_FEATURES
+    if cpu_feature_cache is None:
+        cpu_feature_cache = get_cpu_features()
+        print('Found CPU features:', ' '.join(cpu_feature_cache))
+        # Sanity checking
+        assert all(feat in SUPPORTED_CPU_FEATURES
+                   for feat in cpu_feature_cache)
+
+    return feature in cpu_feature_cache
+
+
+if __name__ == '__main__':
+    import sys
+    config.os = sys.argv[1]
+    print(get_cpu_features())
+
diff --git a/testsuite/driver/testlib.py b/testsuite/driver/testlib.py
index 5f84863070..df56d1d685 100644
--- a/testsuite/driver/testlib.py
+++ b/testsuite/driver/testlib.py
@@ -20,6 +20,7 @@ import subprocess
 
 from testglobals import config, ghc_env, default_testopts, brokens, t
 from testutil import strip_quotes, lndir, link_or_copy_file, passed, failBecause, str_fail, str_pass
+from cpu_features import have_cpu_feature
 import perf_notes as Perf
 from perf_notes import MetricChange
 extra_src_files = {'T4198': ['exitminus1.c']} # TODO: See #12223