From b477c5e786e77e0bb34890843dc2c4f3458d4f58 Mon Sep 17 00:00:00 2001
From: Chris Pressey <cpressey@catseye.tc>
Date: Wed, 13 Dec 2017 16:18:36 +0000
Subject: [PATCH] Don't trash `a` in `copy` if `a` is the dest of the `copy`,
 for now.

---
 eg/proto-game.60p          | 21 ++++++++++-----------
 src/sixtypical/analyzer.py |  8 +++++++-
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/eg/proto-game.60p b/eg/proto-game.60p
index 7ffd61c..83a53e5 100644
--- a/eg/proto-game.60p
+++ b/eg/proto-game.60p
@@ -237,17 +237,16 @@ routine player_logic
 
         // check collision.
         copy [ptr] + y, a
-
-        // cmp a, 32
-        // if z {
-        //     copy new_pos, pos
-        //     copy 81, [ptr] + y
-        // } else {
-        //     // copy game_state_game_over, dispatch_game_state
-        // }
-
-        copy 81, [ptr] + y
-        copy new_pos, pos
+        cmp a, 32
+        if z {
+            copy new_pos, pos
+            copy 81, [ptr] + y
+        } else {
+            // copy game_state_game_over, dispatch_game_state
+            trash n
+            trash a
+            trash z
+        }
 
         // FIXME these trashes, strictly speaking, probably shouldn't be needed,
         // but currently the compiler cares too much about values that are
diff --git a/src/sixtypical/analyzer.py b/src/sixtypical/analyzer.py
index e193c46..1272055 100644
--- a/src/sixtypical/analyzer.py
+++ b/src/sixtypical/analyzer.py
@@ -392,6 +392,7 @@ class Analyzer(object):
                 context.assert_meaningful(src.ref, REG_Y)
                 # TODO this will need to be more sophisticated.  the thing ref points to is touched, as well.
                 context.set_touched(src.ref)  # TODO and REG_Y?  if not, why not?
+                context.set_touched(dest)
                 context.set_written(dest)
             elif isinstance(src, LocationRef) and isinstance(dest, IndexedRef):
                 context.assert_meaningful(src, dest.ref, dest.index)
@@ -409,7 +410,12 @@ class Analyzer(object):
                 context.set_written(dest)
 
             context.set_touched(REG_A, FLAG_Z, FLAG_N)
-            context.set_unmeaningful(REG_A, FLAG_Z, FLAG_N)
+            context.set_unmeaningful(FLAG_Z, FLAG_N)
+
+            # FIXME: this is just to support "copy [foo] + y, a".  consider disallowing `a` as something
+            # that can be used in `copy`.  should be using `st` or `ld` instead, probably.
+            if dest != REG_A:
+                context.set_unmeaningful(REG_A)
 
         elif opcode == 'with-sei':
             self.analyze_block(instr.block, context)