From d32f97238c903765dec4e9a9f3cbfa5fd12cded6 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 10 Aug 2026 11:11:18 -0700
Subject: Chapter 25: Modules, Separate Compilation, and SSA Construction

Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: Symious <14933944+symious@users.noreply.github.com>
Co-authored-by: Jun Kawasaki <jun784@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
---
 .../com/seaofnodes/simple/node/MemPhiNode.java     | 62 ++++++++++++++++------
 1 file changed, 45 insertions(+), 17 deletions(-)

(limited to 'src/main/java/com/seaofnodes/simple/node/MemPhiNode.java')

diff --git a/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java b/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java
index 787333d9..cdfaaf97 100644
--- a/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java
+++ b/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java
@@ -1,39 +1,64 @@
 package com.seaofnodes.simple.node;
 
-import com.seaofnodes.simple.codegen.CodeGen;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMem;
+import com.seaofnodes.simple.codegen.GlobalBits;
+import com.seaofnodes.simple.util.BAOS;
 
-/** A Phi for one field alias, parallel to a bulk Phi at the same Region. */
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+
+/** A Phi for one precise memory alias. */
 public class MemPhiNode extends PhiNode {
+
     public final int _alias;
 
     public MemPhiNode(String label, int alias, Node... inputs) {
-        super(label,TypeMem.make(alias,Type.BOTTOM),inputs);
+        super(label, inputs);
         assert alias > 1;
         _alias = alias;
     }
 
-    public MemPhiNode(MemPhiNode phi) { super(phi); _alias = phi._alias; }
+    public MemPhiNode(MemPhiNode phi) {
+        super(phi,phi._label);
+        _alias = phi._alias;
+    }
+
+    @Override public Tag serialTag() { return Tag.MemPhi; }
+
+    @Override
+    public void packed(BAOS baos, HashMap<String,Integer> strs, HashMap<Type,Integer> types,
+                       IdentityHashMap<Node,Integer> anodes) {
+        super.packed(baos,strs,types,anodes);
+        baos.packed2(_alias);
+    }
 
-    @Override public String label() { return "MemPhi_"+_alias; }
+    static Node make(BAOS bais, String[] strs, Type[] types, GlobalBits fileAliases, GlobalBits aliases) {
+        Node[] ins = new Node[bais.packed1()];
+        String label = strs[bais.packed2()];
+        int alias = bais.packed2();
+        if( alias >= GlobalBits.RESERVED ) alias = aliases.map(fileAliases,alias);
+        return new MemPhiNode(label,alias,ins);
+    }
 
-    @Override public Type compute() {
+    @Override
+    public Type compute() {
+        Type t = super.compute();
         assert BulkMemPhiNode.checkMem(this,_alias);
-        if( !(region() instanceof RegionNode r) )
-            return (region()._type==Type.XCONTROL || region()._type==Type.TOP) ? TypeMem.TOP : _type;
-        if( r.inProgress() ) return r instanceof LoopNode ? _minType : TypeMem.BOT;
-        Type t = Type.TOP;
-        for( int i=1; i<nIns(); i++ )
-            if( addDep(r.in(i))._type!=Type.XCONTROL && r.in(i)._type!=Type.TOP )
-                t = t.meet(MemMergeNode.contents(in(i),_alias,this));
-        return TypeMem.make(_alias,t);
+        if( !(t instanceof TypeMem tmem) ) return t;
+        assert tmem._alias==1 || tmem._alias==_alias;
+        // This Phi structurally knows its alias, but not whether the field is
+        // final.  Do not infer slice finality from evolving input types.
+        return TypeMem.make(_alias,tmem._t,tmem._one,tmem._clz,false,tmem._escFs,tmem._escAs);
     }
 
-    @Override public Node idealize() {
+    @Override
+    public Node idealize() {
+        // A precise memory Phi can always bypass a MemMerge and select its
+        // matching slice.
         for( int i=1; i<nIns(); i++ )
             if( in(i) instanceof MemMergeNode mem ) {
-                setDef(i,CodeGen.CODE.add(mem.alias(_alias)));
+                setDef(i,mem.alias(_alias));
                 return this;
             }
         if( nIns()==3 && region() instanceof LoopNode loop && !loop.inProgress() &&
@@ -44,6 +69,9 @@ public class MemPhiNode extends PhiNode {
         return super.idealize();
     }
 
-    @Override public boolean eq(Node n) { return _alias==((MemPhiNode)n)._alias && super.eq(n); }
+    @Override public boolean eq(Node n) {
+        return _alias==((MemPhiNode)n)._alias && super.eq(n);
+    }
+
     @Override int hash() { return _alias; }
 }
-- 
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