From 52b1ac4ea335d9763376f988199ce75cda09ba38 Mon Sep 17 00:00:00 2001
From: jackbackrack <jrb@pobox.com>
Date: Tue, 14 Sep 2021 22:47:41 -0700
Subject: [PATCH] fold literal unbox

---
 compiler/stz-el.stanza | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/compiler/stz-el.stanza b/compiler/stz-el.stanza
index 14ee622bf..9e640bfa2 100644
--- a/compiler/stz-el.stanza
+++ b/compiler/stz-el.stanza
@@ -2845,14 +2845,22 @@ defn box-unbox-fold (epackage:EPackage, gvt:VarTable) -> EPackage :
 
   ;Compute binding table.
   ;Every entry in the binding table, x => e, indicates that
-  ;x is defined exactly once by the EObject or ENewObject instruction.
-  defn binding-table (e:EBody) -> IntTable<EObject|ENewObject> :
-    val table = IntListTable<EObject|ENewObject>()
+  ;x is defined exactly once by the
+  ;EObject, ENewObject, or EDef instruction.
+  defn binding-table (e:EBody) -> IntTable<ELItem> :
+    val table = IntListTable<ELItem>()
     val remove-set = IntSet()
+    defn remove-varloc-vars (i:EIns) :
+      do(add{remove-set, n(_)}, varlocs(i))
     for i in ins(e) do :
-      match(i:EObject|ENewObject) : add(table, n(x(i)), i)
-      else : do(add{remove-set, n(_)}, varlocs(i))
-    to-inttable<EObject|ENewObject> $
+      match(i) :
+        (i:EObject|ENewObject) : add(table, n(x(i)), i)
+        (i:EDef) :
+          match(x(i), y(i)) :
+            (x:EVarLoc, y:ELiteral) : add(table, n(x), y)
+            (x, y) : remove-varloc-vars(i)
+        (i) : remove-varloc-vars(i)
+    to-inttable<ELItem> $
       for entry in table seq? :
         if remove-set[key(entry)] : None()
         else if length(value(entry)) == 1 : One(key(entry) => head(value(entry)))
@@ -2869,7 +2877,7 @@ defn box-unbox-fold (epackage:EPackage, gvt:VarTable) -> EPackage :
   ;field. Calls fail() if not a match.
   defn unbox-object-get (e:EObjectGet,
                          vt:VarTable,
-                         bindings:IntTable<EObject|ENewObject>) -> [EVarLoc, EImm] :
+                         bindings:IntTable<ELItem>) -> [EVarLoc, EImm] :
     val v = y(e) as? EVar
     val o = get?(bindings, n(v)) as? ENewObject
     val value = ys(o)[index(e)]
@@ -2877,18 +2885,24 @@ defn box-unbox-fold (epackage:EPackage, gvt:VarTable) -> EPackage :
     [x(e), value]
 
   ;If the given ELoad expression corresponds to a retrieval
-  ;of a known object field then return the destination and the field.
+  ;of a known object field or literal value then
+  ;return the destination and the field or value.
   ;Calls fail() if not a match.
   defn unbox-load (e:ELoad,
                    vt:VarTable,
-                   bindings:IntTable<EObject|ENewObject>, ) -> [EVarLoc, EImm] :
+                   bindings:IntTable<ELItem>, ) -> [EVarLoc, EImm] :
     val field = loc(e) as? EField
     val v = y(loc(field) as? EDeref) as? EVar
-    val o = get?(bindings, n(v)) as? EObject
-    fail() when mutable-field?(defstruct-table, n(o), index(field))
-    val value = ys(o)[index(field)]
-    fail() when not immutable?(vt,value)      
-    [x(e), value]
+    match(get?(bindings, n(v))) :
+      (o:EObject) :
+        fail() when mutable-field?(defstruct-table, n(o), index(field))
+        val value = ys(o)[index(field)]
+        fail() when not immutable?(vt,value)      
+        [x(e), value]
+      (o:ELiteral) :
+        fail() when (index(field) != 0 or value(o) is-not Byte|Int|Long|Float|Double)
+        [x(e), ELSLiteral(value(o))]
+      (o) : fail()
 
   ;Perform unboxing folds in the given body.
   ;Assumes that all nested bodies have already been folded.