Another CCP bugfix

Fixes analysis of read nodes in CCP; we were previously ignoring the indices but we need to account for their reachability to ensure we properly mark read nodes as unreachable if any of their position arguments are unreachable.

hercules_opt/src/ccp.rs

@@ -845,11 +845,24 @@ fn ccp_flow_function(
         }
         Node::Read {
             collect,
-            indices: _,
-        } => CCPLattice {
-            reachability: inputs[collect.idx()].reachability.clone(),
-            constant: ConstantLattice::bottom(),
-        },
+            indices,
+        } => {
+            let mut reachability = inputs[collect.idx()].reachability.clone();
+            for index in indices.iter() {
+                if let Index::Position(positions) = index {
+                    for position in positions.iter() {
+                        reachability = ReachabilityLattice::join(
+                            &reachability,
+                            &inputs[position.idx()].reachability,
+                        );
+                    }
+                }
+            }
+            CCPLattice {
+                reachability,
+                constant: ConstantLattice::bottom(),
+            }
+        }
         // Projection handles reachability when following an if or match.
         Node::Projection { control, selection } => match &editor.func().nodes[control.idx()] {
             Node::If { control: _, cond } => {