More misc. rodinia opts

• Make GCM not spill ParallelReduce phis.
• Fix unification for inter-device communication.
• Make notion of parallel indices sets more flexible, and use in infer parallel reduce.
• Misc. schedule tweaks.

hercules_opt/src/gcm.rs

@@ -1302,9 +1302,7 @@ enum UTerm {
     Device(Device),
 }
 
-fn unify(
-    mut equations: VecDeque<(UTerm, UTerm)>,
-) -> Result<BTreeMap<NodeID, Device>, (NodeID, NodeID)> {
+fn unify(mut equations: VecDeque<(UTerm, UTerm)>) -> Result<BTreeMap<NodeID, Device>, NodeID> {
     let mut theta = BTreeMap::new();
 
     // First, assign devices to nodes when a rule directly says to.
@@ -1312,7 +1310,11 @@ fn unify(
         let (l, r) = equations.pop_front().unwrap();
         match (l, r) {
             (UTerm::Node(n), UTerm::Device(d)) | (UTerm::Device(d), UTerm::Node(n)) => {
-                theta.insert(n, d);
+                if let Some(old_d) = theta.insert(n, d)
+                    && old_d != d
+                {
+                    return Err(n);
+                }
             }
             _ => equations.push_back((l, r)),
         }
@@ -1333,7 +1335,7 @@ fn unify(
         match (theta.get(&l), theta.get(&r)) {
             (Some(ld), Some(rd)) => {
                 if ld != rd {
-                    return Err((l, r));
+                    return Err(l);
                 } else {
                     no_progress_iters = 0;
                 }
@@ -1545,12 +1547,11 @@ fn color_nodes(
             }
             Some(func_colors)
         }
-        Err(inconsistency) => {
+        Err(id) => {
             // If unification failed, then there's some node using a node in
-            // that's expecting a different type than what it got. Pick one and
-            // add potentially inter-device copies on each def-use edge. We'll
-            // clean these up later.
-            let id = inconsistency.0;
+            // that's expecting a different type than what it got. Add
+            // potentially inter-device copies on each def-use edge. We'll clean
+            // these up later.
             let users: Vec<_> = editor.get_users(id).collect();
             let success = editor.edit(|mut edit| {
                 let cons = edit.add_zero_constant(typing[id.idx()]);