From 7f3b8856119da7e4fd6fc0a9c0c740d7b0b3170f Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 9 Sep 2026 11:41:35 -0700
Subject: Fix some lattice bugs

---
 .../com/seaofnodes/simple/type/TypeFunPtr.java     | 20 ++++++++++++++++++--
 .../java/com/seaofnodes/simple/type/TypeMem.java   | 17 +++++++----------
 .../main/java/com/seaofnodes/simple/type/XInt.java | 22 ++++++++++++----------
 3 files changed, 37 insertions(+), 22 deletions(-)

(limited to 'chapter25/src/main/java/com/seaofnodes')

diff --git a/chapter25/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java b/chapter25/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
index ff52c93b..975bce3d 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/type/TypeFunPtr.java
@@ -59,9 +59,19 @@ public class TypeFunPtr extends TypeNil {
         if( f2==fun ) return fun;
         return VISIT.isEmpty() ? f2.free(fun) : f2.delayFree(fun);
     }
-    public static TypeFunPtr make( boolean nil, Type[] sig, Type ret ) { return make((byte)(nil ? 3 : 2),true,sig,ret, XInt.FULL); }
+    // Trim trailing args which match the default.
+    private static TypeFunPtr makeAdjusted( byte nil, boolean open, Type[] sig, Type ret, int[] fidxs ) {
+        Type def = open ? TypeScalar.BOT : TypeScalar.TOP;
+        int nargs = sig.length;
+        while( nargs > 0 && sig[nargs-1] == def )
+            nargs--;
+        if( nargs != sig.length )
+            sig = nargs == 0 ? ARG_EMPTY : Arrays.copyOf(sig,nargs);
+        return make(nil,open,sig,ret,fidxs);
+    }
+    public static TypeFunPtr make( boolean nil, Type[] sig, Type ret ) { return makeAdjusted((byte)(nil ? 3 : 2),true,sig,ret, XInt.FULL); }
     public static TypeFunPtr make1( byte nil, boolean open, Type[] sig, Type ret, int fidx ) {
-        return make(nil,open,sig,ret,XInt.make(fidx));
+        return makeAdjusted(nil,open,sig,ret,XInt.make(fidx));
     }
 
 
@@ -94,6 +104,12 @@ public class TypeFunPtr extends TypeNil {
         ts.add(CALLOC);
         ts.add(make((byte)2,false,TINT,TypeInteger.I32, XInt.SET1));
         ts.add(make((byte)2,true ,TINT,TypeInteger.BOT, XInt.SET3));
+        ts.add(make1((byte)2,true,
+                     new Type[]{TypeInteger.BOT},
+                     TypeInteger.BOT, 65));
+        ts.add(make1((byte)2,true,
+                     new Type[]{TypeInteger.BOT, TypeScalar.BOT},
+                     TypeInteger.BOT, 65));
     }
 
     private static final Type[] ARG_EMPTY = new Type[0];
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/type/TypeMem.java b/chapter25/src/main/java/com/seaofnodes/simple/type/TypeMem.java
index 420dea55..106dee49 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/type/TypeMem.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/type/TypeMem.java
@@ -111,6 +111,8 @@ public class TypeMem extends Type {
         ts.add(BOT);
         ts.add(SELF_MEM);
         ts.add(START);
+        ts.add(make(2,TypeInteger.ZERO,true,false,true,XInt.EMPTY,XInt.make(2)));
+        ts.add(make(2,TypeInteger.BOT,false,false,false,XInt.EMPTY,XInt.FULL));
     }
 
     @Override
@@ -128,16 +130,11 @@ public class TypeMem extends Type {
         Type mt = _t.meet(that._t);
         int[] fidxs  = XInt.meet( _escFs, that._escFs );
         int[] aliases= XInt.meet( _escAs, that._escAs );
-        // Singleton & class facts are kept only when both sides agree.
-
-        // Final is kept if either side is final, merging a final & non-final
-        // memory can be argued either way here:
-
-        // - Keep it: merging a final & non-final memory means a later Store
-        //   update will be flagged as an error.
-        // - Lose it: merging a final & non-final memory means a later Load
-        //   cannot be promised the memory is unchanging.
-        return make(alias, mt, _one & that._one, _clz & that._clz, _final | that._final, fidxs, aliases);
+        // Singleton and class facts are kept only when both sides agree.
+        // Finality is a low-side fact, and flips on the dual side.
+        boolean highAlias1 = (this._alias==1 && this._t.isHigh()) || (that._alias==1 && that._t.isHigh());
+        boolean xfinal = highAlias1 ? (_final & that._final) : (_final | that._final);
+        return make(alias, mt, _one & that._one, _clz & that._clz, xfinal, fidxs, aliases);
     }
 
     @Override
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/type/XInt.java b/chapter25/src/main/java/com/seaofnodes/simple/type/XInt.java
index e3054a73..752c1419 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/type/XInt.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/type/XInt.java
@@ -166,22 +166,24 @@ public abstract class XInt {
         if( xs==ys ) return xs;
         boolean isX=true, isY=true;
         int min = Math.min(xs.length,ys.length);
-        for( int i=1; i<min; i++ ) {
-            if( (xs[i] | ys[i])!=xs[i] ) isX=false;
-            if( (xs[i] | ys[i])!=ys[i] ) isY=false;
+        int max = Math.max(xs.length,ys.length);
+        for( int i=1; i<max; i++ ) {
+            int x = i < xs.length ? xs[i] : isHigh(xs) ? -1 : 0;
+            int y = i < ys.length ? ys[i] : isHigh(ys) ? -1 : 0;
+            if( (x | y)!=x ) isX=false;
+            if( (x | y)!=y ) isY=false;
         }
-        if( !isHigh(xs) && min < ys.length )
-            isX = false; // YS has *some* more bits set, and XS does not
-        if( !isHigh(ys) && min < xs.length )
-            isY = false; // XS has *some* more bits set, and YS does not
         if( isX ) return xs;
         if( isY ) return ys;
         // Get a free one
-        int[] ms = free(Math.max(xs.length,ys.length));
+        int[] ms = free(max);
         for( int i=1; i<min; i++ )
             ms[i] = xs[i] | ys[i];
-        if( min < xs.length )  System.arraycopy(xs,min,ms,min,xs.length-min);
-        if( min < ys.length )  System.arraycopy(ys,min,ms,min,ys.length-min);
+        for( int i=min; i<ms.length; i++ ) {
+            int x = i < xs.length ? xs[i] : isHigh(xs) ? -1 : 0;
+            int y = i < ys.length ? ys[i] : isHigh(ys) ? -1 : 0;
+            ms[i] = x | y;
+        }
         return intern(ms);
     }
 
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