Data-parallel multi-core RT codegen

• Use prettyplease to auto-format generated RT Rust code.
• Refactor RT backend to allow for nested async closure environments.
• Lower fork, join, thread ID, and reduce nodes in RT backend (only ParallelFork and ParallelReduce nodes though!).
• QOL make sure there's an entry for start node in fork join nests.
• Add __RawPtrSendSync to hercules_rt and in generated RT code to move pointers across async boundaries.
• Re-schedule test6 in fork_join_tests to generate a tiled fork-join, half in RT code and half in CPU code to test multicore.

hercules_cg/src/fork_tree.rs

@@ -3,11 +3,14 @@ use std::collections::{HashMap, HashSet};
 use crate::*;
 
 /*
- * Construct a map from fork node to all control nodes (including itself) satisfying:
- * a) domination by F
- * b) no domination by F's join
- * c) no domination by any other fork that's also dominated by F, where we do count self-domination
- * Here too we include the non-fork start node, as key for all controls outside any fork.
+ * Construct a map from fork node to all control nodes (including itself)
+ * satisfying:
+ * 1. Dominated by the fork.
+ * 2. Not dominated by the fork's join.
+ * 3. Not dominated by any other fork that's also dominated by the fork, where
+ *    we do count self-domination.
+ * We include the non-fork start node as the key for all control nodes outside
+ * any fork.
  */
 pub fn fork_control_map(
     fork_join_nesting: &HashMap<NodeID, Vec<NodeID>>,
@@ -23,11 +26,14 @@ pub fn fork_control_map(
     fork_control_map
 }
 
-/* Construct a map from each fork node F to all forks satisfying:
- * a) domination by F
- * b) no domination by F's join
- * c) no domination by any other fork that's also dominated by F, where we don't count self-domination
- * Note that the fork_tree also includes the non-fork start node, as unique root node.
+/*
+ * Construct a map from fork node to all fork nodes (including itself)
+ * satisfying:
+ * 1. Dominated by the fork.
+ * 2. Not dominated by the fork's join.
+ * 3. Not dominated by any other fork that's also dominated by the fork, where
+ *    we do count self-domination.
+ * Note that the fork tree also includes the start node as the unique root node.
  */
 pub fn fork_tree(
     function: &Function,
@@ -44,5 +50,6 @@ pub fn fork_tree(
                 .insert(*control);
         }
     }
+    fork_tree.entry(NodeID::new(0)).or_default();
     fork_tree
 }