1 files changed, 77 insertions, 22 deletions

diff --git a/Notes/MIR-Optimisations.md b/Notes/MIR-Optimisations.md
index 759bfa2e..e83f7cd3 100644
--- a/Notes/MIR-Optimisations.md
+++ b/Notes/MIR-Optimisations.md
@@ -19,8 +19,8 @@ At the end of the block, remove original tuple assignment and propagate the valu
 
 
 
-De-Temporary
-============
+De-Temporary (version 1)
+========================
 
 Purpose: Eliminate useless temporaries
 ```
@@ -31,20 +31,19 @@ _2 = foo(_1)
 Algorithm
 ---------
 
-Where the pattern `Local(N) = Use(...)` is seen, record that statement as the assignment for `Local(N)`.
+- Where the pattern `Local(N) = Use(...)` is seen, record that statement as the assignment for `Local(N)`.
+- Detect any uses of `Local(N)` in mutation context (e.g. `Field(Local(N), 0) = ...`) or as a borrow and remove from the
+  list (as these cause the local to diverge from its source).
+- Detect any by-value or mutation uses of the origin value that would mean that moving the assignment forwards would
+  lead to a use-after-free or incorrect value.
 
-Detect any uses of `Local(N)` in mutation context (e.g. `Field(Local(N), 0) = ...`) or as a borrow and remove from the
-list (as these cause the local to diverge from its source).
-
-Detect any by-value or mutation uses of the origin value that would mean that moving the assignment forwards would
-lead to a use-after-free or incorrect value.
-
-If a recorded local is used, replace that usage by the original source. If the value was !Copy, and the use is a move,
- delete the original assignment.
-- CATCH: Detecting a by-move of !Copy is hard when a Copy value is used from a !Copy struct, needs knowledge of the
-  types involved.
-- CATCH: Since partial moves are valid, the !Copy rule above is invalid if it would have been a partial move.
-  - Only allow use of a !Copy result when it's just the slot.
+- Find any uses of locals recorded locals
+  - If this is of a Copy value, the replacement
+    - Copy values can be reused freely
+  - If the value is used at the top level of the source RValue, do the replacemnet and remove the record
+    - !Copy value moved, so can't be moved again.
+  - Otherwise, remove the record
+    - The value was used, so then assignment can't be replaced with later and deleted.
 
 Pseudocode
 ----------
@@ -67,15 +66,22 @@ for stmt in block.statements
 fn do_replacements(stmt)
 {
     visit_lvalues(stmt, |lv, usage| {
-        // 1. Check if Copy (if it is, don't delete any referenced values)
-        delete = (usage == Move && !lv_is_copy(lv));
-        // 2. Search for replacements
+        top_level = true;
+        // 1. Search for replacements
         visit_lvalues(lv, |ilv, usage2| {
             if Local(i) == ilv {
-               ilv = replacement;
-               if delete {
-                    remove_replacement;
-               }
+                if replacement = find_replacement(i) {
+                    if is_copy(ilv) {
+                        ilv = replacement
+                    }
+                    else if top_level {
+                        ilv = replacement
+                        remove_replacement(i)
+                    }
+                    else {
+                        remove_replacement(i)
+                    }
+                }
             }
             });
         // Early-return (don't recuse)
@@ -95,6 +101,13 @@ Locate `RETURN = Local(N)` and replace use of Local(N) as assignment destination
 
 Note: Only replace assignments that are setting the value that will become the return value.
 
+Algorithm
+---------
+TODO: 
+
+Pseudocode
+----------
+TODO: 
 
 
 Dead Assignment Elimination
@@ -104,14 +117,56 @@ Purpose: Remove dead code from previous passes
 
 Remove assignments where the assigned value isn't read/borrowed before next assign
 
+Algorithm
+---------
+
+Pseudocode
+---------
+
+Dead Drop Flag Elimination
+==========================
+
+Purpose: Remove unused (or unchanged) drop flags
+
+Algorithm
+---------
+- Enumerate all changes to drop flags
+- If a flag is never set, replace all uses with its default and delete
+- If a flag is never used, delete
+
+
 Constant Propagation
 ====================
 
 Purpose: Allow deletion of useless code (`if false`) and expansion of `size_of` (and relevant optimisations)
 
+Algorithm
+---------
+- Track assignments of slots with constants
+- Erase record if the slot is invalidated
+- Replace usage of the slot where possible with the constant
+- Evaluate BinOps with both arguments a known slot
+
 
 Value Forward Propagation
 =========================
 
 Purpose: Determine when a value has the same value in all paths to a BB and move the assignment into that BB
 
+Inlining
+========
+
+Purpose: Inline simple methods
+
+Algorithm
+---------
+- For each function call:
+- Check if the called function is simple enough to be inlined
+  - A single BB - inline
+  - Three bbs (first being a function call) - inline
+  - First bb ends with a switch of a constant parameter, and all arms point to return or a return bb
+
+CFG Simplification
+==================
+Purpose: Remove gotos to blocks that only have a single use
+