Workaround and cover issues with -msse4/-mno-sse4

resolve_march_native/engine.py

@@ -3,6 +3,7 @@
 
 import subprocess
 import sys
+from contextlib import suppress
 
 from .parser import extract_flags
 from .runner import run
@@ -127,6 +128,11 @@ def _resolve(self, march_native_flag_set, march_explicit_flag_set, arch, options
         self._process_flags_explicit_has_more(native_unrolled_flag_set,
                                               march_native_flag_set, march_explicit_flag_set)
 
+        # Workaround issues with tribool for machines with e.g. SSE4.1 but not SSE4.2
+        for flag_prefix in ('-m', '-mno-'):
+            with suppress(KeyError):
+                native_unrolled_flag_set.remove(f"{flag_prefix}sse4")
+
         return native_unrolled_flag_set
 
     def run(self, options):

resolve_march_native/test/test_engine.py

@@ -424,3 +424,22 @@ def test_pentium(self):
             'pentium-m--target-help--native.txt',
             'pentium-m--target-help--explicit.txt',
         )
+
+    def test_sse4_weirdness_issue_177(self):
+        expected_flag_set = {
+            # No "-msse4" here!
+            '-msse4.1',
+            '-mxsave',
+            '--param=l1-cache-size=32',
+            '--param=l1-cache-line-size=64',
+            '--param=l2-cache-size=6144',
+            '-march=core2',
+        }
+
+        self._test_engine(
+            expected_flag_set,
+            'harpertown-core2--assembly--native.txt',
+            'harpertown-core2--assembly--explicit.txt',
+            'harpertown-core2--target-help--native.txt',
+            'harpertown-core2--target-help--explicit.txt',
+        )