Deduplicate specs in SideMetadataSanity::get_all_specs (#1342)

For 32 bits chunked side metadata, we check the total size of side
metadata per chunk to make sure it won't get too large.

https://github.com/mmtk/mmtk-core/blob/1dc681561097688ac37382b1e23e56f2d160b7c7/src/util/metadata/side_metadata/sanity.rs#L112

However, the function `get_all_specs` collects all the side metadata
specs from all the policies, and different policies may use the same
local side metadata. This results in duplicate entries in the vec, and
results in incorrect total size calculated based on the vec. This PR
fixes this.

Author: qinsoon

src/util/metadata/side_metadata/sanity.rs

@@ -232,8 +232,10 @@ impl SideMetadataSanity {
                 specs.append(&mut (*v).clone());
             }
         }
-
-        specs
+        // Deduplicate the specs using a hashset
+        std::collections::HashSet::<SideMetadataSpec>::from_iter(specs)
+            .into_iter()
+            .collect()
     }
 
     /// Verifies that all local side metadata specs:
@@ -852,4 +854,34 @@ mod tests {
         assert!(verify_local_specs_size(&[spec_1, spec_1]).is_err());
         assert!(verify_local_specs_size(&[spec_1, spec_1, spec_1, spec_1, spec_1]).is_err());
     }
+
+    #[test]
+    fn test_side_metadata_sanity_get_all_local_specs() {
+        let spec_1 = SideMetadataSpec {
+            name: "spec_1",
+            is_global: false,
+            offset: SideMetadataOffset::rel(0),
+            log_num_of_bits: 0,
+            log_bytes_in_region: 0,
+        };
+
+        let mut sanity = SideMetadataSanity::new();
+        sanity.verify_metadata_context(
+            "policy1",
+            &SideMetadataContext {
+                global: vec![],
+                local: vec![spec_1],
+            },
+        );
+        sanity.verify_metadata_context(
+            "policy2",
+            &SideMetadataContext {
+                global: vec![],
+                local: vec![spec_1],
+            },
+        );
+
+        let local_specs = sanity.get_all_specs(false);
+        assert_eq!(local_specs.len(), 1);
+    }
 }