hdl._ir: chain Fragment.origins with preexisting [0.5 backport]

By chaining, `Fragment.origins` gets tracked through `FragmentTransformer`s

Author: rroohhh

amaranth/hdl/_ir.py

@@ -54,7 +54,7 @@ def get(obj, platform):
         while True:
             if isinstance(obj, Fragment):
                 if hasattr(obj, "origins"):
-                    obj.origins = tuple(origins)
+                    obj.origins = tuple(origins) + (obj.origins or ())
                 return obj
             elif isinstance(obj, Elaboratable):
                 code = obj.elaborate.__code__

tests/test_hdl_ir.py

@@ -1079,12 +1079,31 @@ def test_origins(self):
         self.assertIs(frag.origins[1], elab2)
         self.assertIs(frag.origins[2], m)
 
+    def test_origins_transformed_elaboratable(self):
+        renamed = DomainRenamer("sync")(elab1 := ElaboratesTo(elab2 := ElaboratesTo(m := Module())))
+        frag = Fragment.get(renamed, platform=None)
+        self.assertEqual(len(frag.origins), 4)
+        self.assertIsInstance(frag.origins, tuple)
+        self.assertIs(frag.origins[0], renamed)
+        self.assertIs(frag.origins[1], elab1)
+        self.assertIs(frag.origins[2], elab2)
+        self.assertIs(frag.origins[3], m)
+
+        renamed_nested = ElaboratesTo(elab2 := ElaboratesTo(renamed := DomainRenamer("sync")(m := Module())))
+        frag = Fragment.get(renamed_nested, platform=None)
+        self.assertEqual(len(frag.origins), 4)
+        self.assertIsInstance(frag.origins, tuple)
+        self.assertIs(frag.origins[0], renamed_nested)
+        self.assertIs(frag.origins[1], elab2)
+        self.assertIs(frag.origins[2], renamed)
+        self.assertIs(frag.origins[3], m)
+
     def test_origins_disable(self):
         inst = Instance("test")
         del inst.origins
         elab = ElaboratesTo(inst)
         frag = Fragment.get(elab, platform=None)
-        self.assertFalse(hasattr(frag, "_origins"))
+        self.assertFalse(hasattr(frag, "origins"))
 
 
 class IOBufferTestCase(FHDLTestCase):