fix: madhyasthal: enable escape analysis pass; do not alias copy if source is an escapee

Author: xTrayambak

src/bali/runtime/compiler/amd64/midtier.nim

@@ -323,7 +323,10 @@ proc compile*(
 
   var pipeline = Pipeline(fn: &lowered)
   pipeline.optimize(
-    {Passes.NaiveDeadCodeElim, Passes.AlgebraicSimplification, Passes.CopyPropagation}
+    {
+      Passes.NaiveDeadCodeElim, Passes.AlgebraicSimplification, Passes.EscapeAnalysis,
+      Passes.CopyPropagation,
+    }
   )
 
   return compileLowered(cgen, pipeline)

src/bali/runtime/compiler/madhyasthal/copy_propagation.nim

@@ -2,7 +2,7 @@
 ##
 ## The basic idea behind this pass is that the middle-end (AST -> Bytecode / "Niche") generates a lot of unnecessary
 ## copy instructions. We can safely* eliminate these unnecessary copies if we can prove that the copied destination
-## is unworthy of copying (it is never mutated)
+## is unworthy of copying (it is never mutated AND it is locally defined)
 ##
 ## Copyright (C) 2025 Trayambak Rai (xtrayambak at disroot dot org)
 import std/[sets]
@@ -53,6 +53,12 @@ func eliminateUnmutatedCopies*(
         # Any attempts to eliminate this copy will cause semantic breakage.
         continue
 
+      if copy.dest notin pipeline.info.esc.locals:
+        # If the register is not locally owned, we cannot
+        # safely alias the copy as it might end up mutating
+        # a global state, which'd cause semantic breakage.
+        continue
+
       unmutated.incl(copy)
 
   ensureMove(unmutated)