From c4dcf6f751b35c7a2a3b46fa2d69b95d37d082a6 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 30 Sep 2026 19:25:04 -0700
Subject: Finish forward-port mem ops thru ch25

---
 .../simple/codegen/GlobalCodeMotion.java           |  49 ++---
 .../com/seaofnodes/simple/node/BulkMemPhiNode.java |   2 +-
 .../java/com/seaofnodes/simple/node/LoadNode.java  | 238 +++++++++++----------
 .../java/com/seaofnodes/simple/node/MemOpNode.java |  34 +++
 .../main/java/com/seaofnodes/simple/node/Node.java |   1 +
 .../java/com/seaofnodes/simple/node/PhiNode.java   | 106 ++++-----
 .../com/seaofnodes/simple/node/RegionNode.java     |   2 +-
 .../java/com/seaofnodes/simple/node/StoreNode.java |   4 +
 .../simple/node/cpus/x86_64_v2/LoadX86.java        |   5 +
 .../java/com/seaofnodes/simple/Chapter11Test.java  |   2 +
 .../java/com/seaofnodes/simple/Chapter20Test.java  |   2 +-
 .../java/com/seaofnodes/simple/Chapter21Test.java  |   4 +-
 .../test/java/com/seaofnodes/simple/EvalArm64.java |   7 +-
 .../com/seaofnodes/simple/MemoryEncodingTest.java  | 104 +++++++++
 14 files changed, 368 insertions(+), 192 deletions(-)
 create mode 100644 chapter25/src/test/java/com/seaofnodes/simple/MemoryEncodingTest.java

(limited to 'chapter25/src')

diff --git a/chapter25/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java b/chapter25/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
index ecd23c1e..484bcaa9 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/codegen/GlobalCodeMotion.java
@@ -172,17 +172,9 @@ public abstract class GlobalCodeMotion {
 
                 // Loads need their memory inputs' uses also done
                 if( n instanceof MemOpNode ld && ld._isLoad )
-                    for( Node memuse : ld.mem()._outputs )
-                        if( late[memuse._nid]==null &&
-                            // New makes new memory, never crushes load memory
-                            !(memuse instanceof NewNode) &&
-                            // Load-use directly defines memory
-                            (memuse._type instanceof TypeMem ||
-                             // Load-use directly defines memory
-                             memuse instanceof CallNode) ) {
-                            assert !( memuse._type instanceof TypeTuple tt && tt._types[ld._alias] instanceof TypeMem );
+                    for( Node memuse : ld.antiDeps() )
+                        if( late[memuse._nid]==null )
                             continue outer;
-                        }
 
                 // All uses done, schedule
                 _doSchedLate(n,ns,late,anti);
@@ -193,9 +185,7 @@ public abstract class GlobalCodeMotion {
             for( Node def : n._inputs ) {
                 if( def==null ) continue;
                 if( late[def._nid]==null ) work.push(def);
-                for( Node out : def._outputs )
-                    if( out instanceof MemOpNode ld && ld._isLoad && late[ld._nid]==null )
-                        work.push(ld);
+                wakeLoads(def,late,work,new BitSet());
             }
             if( n instanceof LoopNode loop )
                 for( Node phi : loop._outputs )
@@ -255,25 +245,32 @@ public abstract class GlobalCodeMotion {
             best instanceof IfNode;
     }
 
+    // A writer may consume a load's memory through an aggregate.
+    private static void wakeLoads(Node def, CFGNode[] late, WorkList<Node> work, BitSet visit) {
+        if( visit.get(def._nid) ) return;
+        visit.set(def._nid);
+        for( Node out : def._outputs )
+            if( out instanceof MemOpNode ld && ld._isLoad && late[ld._nid]==null ) work.push(ld);
+        if( def instanceof MemMergeNode )
+            for( int i=1; i<def.nIns(); i++ )
+                if( def.in(i)!=null ) wakeLoads(def.in(i),late,work,visit);
+    }
+
     private static CFGNode find_anti_dep(CFGNode lca, MemOpNode load, CFGNode early, CFGNode[] late, int[] anti) {
         // We could skip final-field loads here.
         // Walk LCA->early, flagging Load's block location choices
         for( CFGNode cfg=lca; cfg!=early.idom(); cfg = cfg.idom() )
             anti[cfg._nid] = load._nid;
         // Walk load->mem uses, looking for Stores causing an anti-dep
-        for( Node mem : load.mem()._outputs ) {
+        for( Node mem : load.antiDeps() ) {
             switch( mem ) {
             case MemOpNode st:
-                if( !st._isLoad && load._alias == st._alias ) {
-                    assert late[mem._nid] != null;
-                    lca = anti_dep(load,late[mem._nid],lca,st,anti);
-                }
-                break; // Loads do not cause anti-deps on other loads
-            case EscapeNode esc:
-                if( load._alias == esc.fld()._alias ) {
-                    assert late[mem._nid] != null;
-                    lca = anti_dep(load,late[mem._nid],lca,mem,anti);
-                }
+                assert late[st._nid]!=null;
+                lca = anti_dep(load,late[st._nid],lca,st,anti);
+                break;
+            case EscapeNode st:
+                assert late[st._nid]!=null;
+                lca = anti_dep(load,late[st._nid],lca,st,anti);
                 break;
             case CallNode call:
                 assert late[call._nid]!=null;
@@ -286,8 +283,6 @@ public abstract class GlobalCodeMotion {
                     if( phi.in(i)==load.mem() )
                         lca = anti_dep(load,phi.region().cfg(i),lca,null,anti);
                 break;
-            case ReturnNode ret: break; // Load must already be ahead of Return
-            case MemMergeNode ret: break; // Mem uses now on ScopeMin
             default: throw Utils.TODO("Should not reach here");
             }
         }
@@ -299,7 +294,7 @@ public abstract class GlobalCodeMotion {
         // Stores are already placed.  Constrain the load at that block only.
         if( anti[stblk._nid]==load._nid ) {
             lca = stblk.domLCA(lca,null);
-            if( lca==stblk && st!=null && st._inputs.find(load) == -1 )
+            if( lca==stblk && st!=null && !(st instanceof CallNode) && st._inputs.find(load) == -1 )
                 st.addDef(load); // Same-block load must precede the store.
         }
         return lca;
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java
index cabf7d69..82c4af10 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java
@@ -253,7 +253,7 @@ public class BulkMemPhiNode extends PhiNode {
         mphi.setType(TypeMem.BOT.makeFrom(alias));
         for( int i=1; i<nIns(); i++ )
             mphi.addDef(CodeGen.CODE.add(preciseInput(in(i),alias)));
-        return (MemPhiNode)mphi.peephole();
+        return CodeGen.CODE.add(mphi);
     }
 
     MemPhiNode _findPhi(int alias) {
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java
index 193fbe17..85ca42cd 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java
@@ -31,6 +31,25 @@ public class LoadNode extends MemOpNode {
     }
     @Override public Tag serialTag() { return Tag.Load; }
 
+    @Override boolean canDrop(MemOpNode other, Node dep) {
+        return super.canDrop(other,dep) && !clobbered(dep);
+    }
+
+    // Check only immediate memory users. Writers clobber memory; Phis and
+    // aggregates might lead to a clobber, so stop rather than search further.
+    private boolean clobbered(Node dep) {
+        Node mem = mem();
+        dep.addDepForwards(mem);
+        for( Node use : mem._outputs ) {
+            if( use==null ) continue;
+            dep.addDepForwards(use);
+            if( use instanceof StoreNode || use instanceof PhiNode ||
+                use instanceof MemMergeNode ||
+                use instanceof NewNode || use instanceof EscapeNode || use instanceof CallNode ) return true;
+        }
+        return false;
+    }
+
     // Debugger label
     @Override public String  label() { return "ld_"+mlabel(); }
     @Override
@@ -89,10 +108,10 @@ public class LoadNode extends MemOpNode {
         Node mem = mem();
         Node ptr = ptr();
 
-        // Loads into structs do not need a ctrl edge, as null-ptr checking is
-        // baked into the type system.  Loads into arrays DO need the ctrl
-        // edge, at least until proper range-checking is in place.
-        if( in(0)!=null && ptr._type instanceof TypeMemPtr tmp && !tmp._obj.isAry() ) {
+        // Null checks are handled by types. Array elements retain control for
+        // range checks, but reading an array's length has no index to check.
+        if( in(0)!=null && ptr._type instanceof TypeMemPtr tmp &&
+            (!tmp._obj.isAry() || _name.equals("#")) ) {
             setDef(0,null);
             return this;
         }
@@ -112,19 +131,6 @@ public class LoadNode extends MemOpNode {
         if( _alias == 1 )
             return null;
 
-        // External storage is shared even through different class namespaces.
-        boolean external = ptr._type instanceof TypeMemPtr tmp &&
-            (fld=tmp._obj.field(_name)) != null && fld._extern;
-
-        // Simple Load-after-Store on same address.
-        if( mem instanceof StoreNode st &&
-            ptr == st.nnptr() &&
-            off() == st.off() &&  // Must check same object
-            st.val()._type.isa(_type) ) {
-            assert _name.equals(st._name); // Equiv class aliasing is perfect
-            return extend(st.val());
-        }
-
         if( mem instanceof MemMergeNode merge ) {
             setDef(1,merge.alias(_alias));
             // In support of uplifting control to a prior dominating load, if
@@ -144,67 +150,9 @@ public class LoadNode extends MemOpNode {
                 addDep(ld)._type.isa(_type) ) // and not rolling backwards
                 return ld;
 
-        // Load-after-Store on same address, but bypassing provably unrelated
-        // stores.  This is a more complex superset of the above two peeps.
-        // "Provably unrelated" is really weak.
-        if( ptr instanceof ReadOnlyNode ro )
-            ptr = ro.in(1);
-        outer:
-        while( true ) {
-            switch( mem ) {
-            case StoreNode st:
-                if( ptr == addDep(st.ptr()) && off() == st.off() )
-                    return extend(castRO(st.val())); // Proved equal
-                // Can we prove unequal?  Offsets do not overlap?
-                if( !off()._type.join(st.off()._type).isHigh() && // Offsets overlap
-                    (external || !neverAlias(ptr,st.ptr())) ) {   // And might alias
-                    addDep(   off());                             // Offsets can fold, proving unequal
-                    addDep(st.off());                             // Offsets can fold, proving unequal
-                    break outer;                                  // Cannot tell, stop trying
-                }
-                // Pointers cannot overlap
-                mem = st.mem(); // Proved never equal
-                break;
-            case PhiNode phi:
-                // Assume related
-                addDep(phi);
-                break outer;
-            case ConstantNode con:
-                // Load from constant memory
-                if( con._con instanceof TypeMem tmem )
-                    throw Utils.TODO("need to see a test case");
-            //        return ConstantNode.make(tmem._t);
-                break outer;  // Assume shortly dead
-            case ProjNode mproj: // Memory projection
-                switch( mproj.in(0) ) {
-                case NewNode nnn1:
-                    if( external ) break outer; // Class allocation does not initialize C storage
-                    // Direct load from fresh zero/default-filled allocation.
-                    Type decl = declaredType();
-                    assert decl!=Type.BOTTOM;
-                    Type zero = decl.makeZero();
-                    assert zero.isa(_type); // Catch bug uninitialized null field
-                    return ConstantNode.make(zero);
-                case CallEndNode cend: addDep(mproj); break outer; // TODO: Bypass no-alias call
-                default: throw Utils.TODO("Should not reach here");
-                }
-            case MemMergeNode merge:  mem = merge.alias(_alias);  break;
-            case EscapeNode esc:
-                if( esc.self()==ptr ) // Proved equal
-                    { mem = esc.priv(); break; }
-                // Mal-formed, dying
-                if( !(esc.self().in(0) instanceof NewNode) )
-                    break outer;
-                // Two NewNodes are always unequal
-                if( ptr.in(0) instanceof NewNode )
-                    { mem = esc.pub(); break; }
-                // TODO: Can we prove unequal?
-                break outer;
-
-            default:
-                throw Utils.TODO();
-            }
-        }
+        Node win = find(mem,ptr,null,null);
+        if( win!=null ) return folded(win);
+        if( ptr instanceof ReadOnlyNode ro ) ptr=ro.in(1);
 
         // Push a Load up through a Phi, as long as it collapses on at least
         // one arm.  If at a Loop, the backedge MUST collapse - else we risk
@@ -213,34 +161,119 @@ public class LoadNode extends MemOpNode {
         //   if( pred ) ptr.x = e0;         val = pred ? e0
         //   else       ptr.x = e1;                    : e1;
         //   val = ptr.x;                   ptr.x = val;
-        if( mem instanceof PhiNode memphi && memphi.region()._type == Type.CONTROL && memphi.nIns()== 3 &&
+        if( mem() instanceof MemPhiNode memphi && memphi.region()._type == Type.CONTROL && memphi.nIns()== 3 &&
+            // Array access control must not be moved across the merge.
+            in(0)==null &&
             // Offset can be hoisted
             off() instanceof ConstantNode &&
-            // Not control dependent
-            in(0)==null &&
             // Pointer can be hoisted
             hoistPtr(ptr,memphi)  ) {
 
-            // Profit on RHS/Loop backedge
-            if( profit(memphi,2) ||
-                // Else must not be a loop to count profit on LHS.
-                (!(memphi.region() instanceof LoopNode) && profit(memphi,1)) ) {
-                Node ld1 = ld(1);
-                Node ld2 = ld(2);
-                PhiNode phi = new PhiNode(_name, memphi.region(),ld1,ld2);
-                phi.setType(phi.compute().join(_type));
-                return phi;
+            // Returning to this memory means no change only if the pointer
+            // is also loop invariant. A pointer Phi may select another object.
+            Node stop = memphi.region() instanceof LoopNode &&
+                !(ptr instanceof PhiNode p && p.region()==memphi.region()) ? memphi : null;
+            if( find(memphi.in(2),ptr,stop,new BitSet())!=null ||
+                (!(memphi.region() instanceof LoopNode) && find(memphi.in(1),ptr,null,new BitSet())!=null) ) {
+                // Integer loop Phis widen to i64. Keep the load's declared
+                // width at the result, as for ordinary typed loop variables.
+                if( _type instanceof TypeInteger && !declaredType().isa(_type) ) return null;
+                PhiNode phi = new PhiNode(_name,memphi.region()).keep();
+                phi.setType(_type instanceof TypeInteger ? TypeInteger.BOT : _type);
+                for( int i=1; i<memphi.nIns(); i++ ) {
+                    Node p = ptr instanceof PhiNode pp && pp.region()==memphi.region() ? pp.in(i) : ptr;
+                    phi.addDef(load(memphi.in(i),p,stop,phi));
+                }
+                CodeGen.CODE.add(phi.unkeep());
+                return _type instanceof TypeInteger ? new ConvertNode(declaredType(),phi) : phi;
             }
         }
 
         return null;
     }
 
-    private Node ld( int idx ) {
-        Node mem = mem(), ptr = ptr();
-        assert in(0)==null;
-        assert !(ptr instanceof PhiNode && ptr.in(0)==mem.in(0)); // If fails, need to use pre-merged ptr at same phi
-        return new LoadNode(_loc,_name,_alias,null,mem.in(idx),ptr, off()).peephole();
+    // Load a flavored zero from a New
+    private Node zero(NewNode nnn) {
+        Type zero = declaredType().makeZero();
+        assert zero.isa(_type); // Catch an uninitialized non-null field
+        return castRO(new ConstantNode(zero).peephole());
+    }
+
+    // Search only; no new nodes or rewiring. Return a Store/New that folds,
+    // the unchanged loop memory, or a merge whose every arm folds. Null fails.
+    // Register dependencies so a later pointer/offset rewrite retries the query.
+    private Node find(Node mem, Node ptr, Node stop, BitSet visit) {
+        if( ptr instanceof ReadOnlyNode ro ) ptr=ro.in(1);
+        Field fld;
+        boolean external = ptr._type instanceof TypeMemPtr tmp &&
+            (fld=tmp._obj.field(_name))!=null && fld._extern;
+        while( mem!=null ) {
+            addDep(mem);
+            if( mem==stop ) return mem;
+            switch( mem ) {
+            case MemMergeNode merge: mem=merge.alias(_alias); break;
+            case StoreNode st:
+                // Alias 1 is still unresolved, not a proven different field.
+                if( st._alias==1 ) return null;
+                addDep(st.ptr());
+                if( _alias==st._alias && (ptr==st.ptr() || ptr==st.nnptr()) && off()==st.off() ) {
+                    // A full-width load cannot narrow the forwarded value.
+                    if( declaredType() instanceof TypeInteger ti && ti.log_size()==3 &&
+                        !addDep(st.val())._type.isa(_type) ) return null;
+                    return st;
+                }
+                if( (external || _alias==st._alias) && (external || !neverAlias(ptr,st.ptr())) &&
+                    !addDep(off())._type.join(addDep(st.off())._type).isHigh() ) return null;
+                mem=st.mem();
+                break;
+            case ProjNode proj:
+                // New's memory is private; public memory is joined at Escape.
+                if( external || !(proj.in(0) instanceof NewNode nnn) ) return null;
+                if( declaredType()==Type.BOTTOM ) return null;
+                return nnn;
+            case EscapeNode esc:
+                if( external ) return null;
+                addDep(esc.self());
+                if( esc.self()==ptr ) { mem=esc.priv(); break; }
+                if( neverAlias(ptr,esc.self()) ) { mem=esc.pub(); break; }
+                return null;
+            case MemPhiNode phi:
+                addDep(phi.region());
+                // Only the original loop closes a successful cycle. Another
+                // loop or an unfinished merge needs a separate proof.
+                if( visit==null || !(phi.region() instanceof RegionNode r) || r instanceof LoopNode ||
+                    r.inProgress() || phi.inProgress() || r._type!=Type.CONTROL ) return null;
+                if( visit.get(phi._nid) ) return phi; // Already proved every arm.
+                for( int i=1; i<phi.nIns(); i++ )
+                    if( find(phi.in(i),ptr,stop,visit)==null ) return null;
+                visit.set(phi._nid);
+                return phi;
+            default: return null;
+            }
+        }
+        return null;
+    }
+
+    private Node folded(Node win) {
+        return win instanceof StoreNode st ? extend(castRO(st.val())) : zero((NewNode)win);
+    }
+
+    // Materialize only after the profitability search succeeds. The value Phi
+    // stands for a load which comes back around the loop with unchanged memory.
+    private Node load(Node mem, Node ptr, Node stop, PhiNode value) {
+        Node win=find(mem,ptr,stop,new BitSet());
+        if( win!=null ) {
+            if( win==stop ) return value;
+            if( win instanceof MemPhiNode mp ) {
+                PhiNode phi=new PhiNode(_name,mp.region()).keep();
+                for( int i=1; i<mp.nIns(); i++ ) phi.addDef(load(mp.in(i),ptr,stop,value));
+                return CodeGen.CODE.add(phi.unkeep().peephole());
+            }
+            Node fold=folded(win);
+            if( fold!=null ) return fold.peephole();
+        }
+        LoadNode ld=new LoadNode(_loc,_name,_alias,in(0),mem,ptr,off());
+        return ld.peephole();
     }
 
     private static boolean neverAlias( Node ptr1, Node ptr2 ) {
@@ -269,21 +302,6 @@ public class LoadNode extends MemOpNode {
         return false;
     }
 
-    // Profitable if we find a matching Store on this Phi arm.
-    private boolean profit(PhiNode memphi, int idx) {
-        Node px = memphi.in(idx);
-        if( px==null ) return false;
-        // Memory is collapsing, no bother
-        if( px._type instanceof TypeMem mem && mem._t.isHighOrConst() )
-            return false;
-        if( px instanceof StoreNode st1 && ptr()==addDep(st1.nnptr() ) && off()==st1.off() && addDep(st1.val())._type.isa(_type) )
-            // To avoid cyclic pushing a Load up then down, getting here means
-            // the load *must* match against the Store
-            return true;
-        addDep(px);
-        return false;
-    }
-
     // Read-Only is a deep property, and cannot be cast-away
     private Node castRO(Node rez) {
         if( ptr()._type.isFinal() && !rez._type.isFinal() )
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/MemOpNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/MemOpNode.java
index 441edc3e..de7adede 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/MemOpNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/MemOpNode.java
@@ -8,6 +8,7 @@ import com.seaofnodes.simple.util.BAOS;
 import com.seaofnodes.simple.util.Utils;
 import java.lang.StringBuilder;
 import java.util.BitSet;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.IdentityHashMap;
 
@@ -101,6 +102,13 @@ public abstract class MemOpNode extends TypeNode {
     public StringBuilder _printMach( StringBuilder sb, BitSet visited ) { throw Utils.TODO(); }
 
 
+    // Extra conditions for factoring matching memory operations through a Phi.
+    // The caller has already checked the opcode, input shape and control.
+    boolean canDrop(MemOpNode other, Node dep) {
+        dep.addDep(ptr());
+        return _alias>1 && _alias==other._alias && declaredType()==other.declaredType() && err()==null;
+    }
+
     @Override
     public boolean eq(Node n) {
         MemOpNode mem = (MemOpNode)n; // Invariant
@@ -128,4 +136,30 @@ public abstract class MemOpNode extends TypeNode {
         return null;
 
     }
+
+    // Memory writers which must follow this read. A packaging node is not a
+    // write; follow this alias through aggregates to its writers.
+    public ArrayList<Node> antiDeps() {
+        ArrayList<Node> deps = new ArrayList<>();
+        antiDeps(mem(),deps,new BitSet());
+        return deps;
+    }
+
+    private void antiDeps(Node mem, ArrayList<Node> deps, BitSet visit) {
+        if( visit.get(mem._nid) ) return;
+        visit.set(mem._nid);
+        for( Node use : mem._outputs ) {
+            if( use instanceof MemMergeNode merge ) {
+                Node slice = _alias<merge.nIns() ? merge.in(_alias) : null;
+                if( (slice==mem) || (slice==null && merge.in(1)==mem) )
+                    antiDeps(merge,deps,visit);
+            } else if( use instanceof CallNode ||
+                       (use instanceof MemOpNode st && !st._isLoad && st._alias==_alias) ||
+                       (use instanceof EscapeNode esc && esc.fld()._alias==_alias) ||
+                       (use instanceof MemPhiNode phi && phi._alias==_alias) ||
+                       (use instanceof BulkMemPhiNode phi && !phi.isSplit(_alias)) ) {
+                if( !deps.contains(use) ) deps.add(use);
+            }
+        }
+    }
 }
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java
index 59c9f8e3..8842db78 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -306,6 +306,7 @@ public abstract class Node implements Cloneable {
     // Error is 'use' does not exist; ok for 'use' to be null.
     public boolean delUse( Node use ) {
         _outputs.del(_outputs.find(use));
+        moveDepsToWorklist(); // User-count and anti-dependence queries can now change.
         return _outputs.isEmpty();
     }
 
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/PhiNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/PhiNode.java
index a4c73472..9d8adb15 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/PhiNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/PhiNode.java
@@ -154,67 +154,77 @@ public class PhiNode extends Node {
     // Same op on all Phi paths; all ops have only the Phi as a use.
     // None have a control input.
     private boolean same_op() {
-        Node busy=null;
-        if( in(1) instanceof ConstantNode )
-            return false;
-        for( int i=1; i<nIns(); i++ ) {
-            Node op = in(i);
-            if( in(1).getClass() != op.getClass() || op.in(0)!=null || in(1).nIns() != op.nIns() )
-                return false;      // Wrong class or CFG bound or mismatched inputs
-            if( in(1) instanceof MemOpNode mem ) {
-                // Mismatched aliases
-                if( mem._alias != ((MemOpNode)op)._alias ) return false;
-                // Load is clobbered somewhere, and can not be pulled forward past the Phi?
-                if( mem instanceof LoadNode )
-                    for( Node use : op.outs() )
-                        if( use instanceof StoreNode )
-                            return false;
-            }
-            if( in(1) instanceof EscapeNode )
-                return false;
-            if( in(1) instanceof MemMergeNode )
-                return false;   // Have to keep aliases straight
-            if( op.nOuts() > 1 ) {
-                if( busy==null ) busy = op;
-                else {         // Too many users, but addDep in case lose users
-                    for( Node out : op._outputs )
-                        if( out!=null && out!=this )
-                            addDep(out);
-                    for( Node out : busy._outputs )
-                        if( out!=null && out!=this )
-                            addDep(out);
+        Node op = in(1);
+        if( op instanceof EscapeNode || op instanceof CFGNode || op instanceof ConstantNode || op instanceof PhiNode ||
+            op instanceof ProjNode || op instanceof NewNode || op instanceof ScopeNode || op instanceof MemMergeNode ) return false;
+        // A bulk Phi must split its aliases before factoring precise Stores.
+        if( this instanceof BulkMemPhiNode ) return false;
+        // Bulk splitting currently identifies parallel slices by Region/alias.
+        // Factoring can introduce another slice at a different memory point;
+        // wait until that Region's bulk partitioning has finished.
+        if( op instanceof MemOpNode )
+            for( Node use : region()._outputs )
+                if( use instanceof BulkMemPhiNode ) {
+                    addDepForwards(use);
                     return false;
                 }
+        Node busy = null;
+        for( int i=1; i<nIns(); i++ ) {
+            Node n = in(i);
+            if( addDep(region().in(i))._type==Type.XCONTROL ||
+                op.getClass()!=n.getClass() || n.nIns()!=op.nIns() || n.in(0)!=null || !op.eq(n) ) return false;
+            if( n instanceof MemOpNode mem && !mem.canDrop((MemOpNode)op,this) ) return false;
+            // Moving a Store must remove the old effect, not duplicate it.
+            // Allow one shared arm: the other arms disappear into the single
+            // factored operation, usually reducing the total operation count.
+            addDepForwards(n);
+            if( n.nOuts()>1 ) {
+                for( Node use : n._outputs )
+                    if( use!=null && use!=this ) addDepForwards(use);
+                if( n instanceof StoreNode || busy!=null ) return false;
+                busy=n;
             }
+            for( int j=1; j<n.nIns(); j++ )
+                if( n.in(j) instanceof ScopeNode || ((n.in(j)==null) != (op.in(j)==null)) ) return false;
         }
         return true;
     }
 
     private Node drop_same_op() {
-        assert !(in(1) instanceof CFGNode);
-        Node op = in(1);
-        Node cp = op.copy();
-        cp._type = null;    // Fresh type
-        cp.addDef(null);    // No control
-
+        Node op = in(1), cp = op.copyEmpty();
+        cp._type = null;
+        cp.addDef(null);
         for( int j=1; j<op.nIns(); j++ ) {
-            boolean needsPhi = false;
-            Node x = op.in(j); // Jth input from sample #1
+            Node x = op.in(j);
+            boolean different = false;
             for( int i=2; i<nIns(); i++ )
-                if( in(i).in(j) != x )
-                    { needsPhi=true; break; }
-            if( needsPhi ) {
-                x = make(_label,op.in(j)._type);
-                x.addDef(region());
-                for( int i=1; i<nIns(); i++ )
-                    x.addDef(in(i).in(j));
-                x = x.peephole();
+                if( in(i).in(j)!=x ) different=true;
+            if( different ) {
+                Node[] ins = new Node[nIns()];
+                ins[0] = region();
+                Type t = Type.TOP;
+                for( int i=1; i<nIns(); i++ ) {
+                    ins[i] = in(i).in(j);
+                    t = t.meet(ins[i]._type);
+                }
+                // Do not introduce an operand Phi mixing incompatible type families.
+                if( t==Type.BOTTOM ) {
+                    for( int i=1; i<ins.length; i++ ) addDep(ins[i]);
+                    cp.kill();
+                    return null;
+                }
+                PhiNode phi = j==1 && op instanceof MemOpNode mem
+                    ? new MemPhiNode(_label,mem._alias,ins)
+                    : PhiNode.make(_label,t,ins);
+                x = phi.peephole();
             }
             cp.addDef(x);
         }
-        // Test not running backwards, which can happen for e.g. And's
-        if( cp.compute().isa(compute()) )
-            return cp;
+        // Factoring must not widen the result (e.g. correlated And operands).
+        if( cp.compute().isa(compute()) ) return cp;
+        for( int i=1; i<nIns(); i++ )
+            for( int j=1; j<in(i).nIns(); j++ )
+                if( in(i).in(j)!=null ) addDep(in(i).in(j));
         cp.kill();
         return null;
     }
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/RegionNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/RegionNode.java
index 32434850..a886183e 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/RegionNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/RegionNode.java
@@ -48,7 +48,7 @@ public class RegionNode extends CFGNode {
         if( !hasPhi() && nIns()>3 &&  // No Phi users, just a control user
                 in(1) instanceof CProjNode p1 &&
                 in(2) instanceof CProjNode p2 &&
-                addDep(p1.in(0))==addDep(p2.in(0)) &&
+                addDepForwards(p1).in(0)==addDepForwards(p2).in(0) &&
                 p1.in(0) instanceof IfNode iff ) {
             // Replace with the iff.ctrl directly
             if( nIns()==3 ) return iff.ctrl();
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/StoreNode.java
index 2683ddf5..fe379c80 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/StoreNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/StoreNode.java
@@ -49,6 +49,10 @@ public class StoreNode extends MemOpNode {
         baos.write(_size);
     }
 
+    @Override boolean canDrop(MemOpNode other, Node dep) {
+        return super.canDrop(other,dep) && _init==((StoreNode)other)._init;
+    }
+
     // Debugger label
     @Override public String  label() { return "st_"+mlabel(); }
     @Override public boolean isMem() { return true; }
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/LoadX86.java b/chapter25/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/LoadX86.java
index c55002c1..aca0eea1 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/LoadX86.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/cpus/x86_64_v2/LoadX86.java
@@ -24,6 +24,11 @@ public class LoadX86 extends MemOpX86 {
     }
 
     static void enc( Encoding enc, Type decl, short dst, short ptr, short idx, int off, int scale ) {
+        // Allocation may put a full-width integer in an XMM register (or a
+        // floating value in a GPR). Move its bits using the selected register bank.
+        if( dst>=x86_64_v2.XMM_OFFSET && decl.log_size()==3 ) decl=TypeFloat.F64;
+        else if( dst<x86_64_v2.XMM_OFFSET && decl instanceof TypeFloat )
+            decl = decl==TypeFloat.F32 ? TypeInteger.U32 : TypeInteger.BOT;
         if( decl == TypeFloat.F32) enc.add1(0xF3);
         if( decl == TypeFloat.F64) enc.add1(0xF2);
 
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter11Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter11Test.java
index 2e661901..d515df8d 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter11Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter11Test.java
@@ -152,6 +152,8 @@ return v.f;
 """);
         code.parse().opto();
         assertEquals("return Phi(Loop,0,2);", code.print());
+        for( int arg : new int[]{-1,0,1,3,100} )
+            assertEquals("0",Eval2.eval(code,arg));
     }
 
     @Test
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
index ce604cf1..e39c09e7 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
@@ -183,7 +183,7 @@ for( int i=0; i<ary#-1; i++ )
 return ary[1] * 1000 + ary[3]; // 1 * 1000 + 6
 """;
         testCPU(src,"x86_64_v2", "SystemV",-1,"return mov(.[]);");
-        testCPU(src,"riscv"    , "SystemV", 7,"return (add,.[],(mul,.[],1000));");
+        testCPU(src,"riscv"    , "SystemV", 9,"return (add,.[],(mul,.[],1000));");
         testCPU(src,"arm"      , "SystemV", 5,"return (add,.[],(mul,.[],1000));");
     }
 
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
index b88e8af9..08da0654 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
@@ -279,7 +279,7 @@ for( int i=0; i<ary#-1; i++ )
 return ary[1] * 1000 + ary[3]; // 1 * 1000 + 6
 """;
         testCPU(src,"x86_64_v2", "SystemV",-1,"return mov(.[]);");
-        testCPU(src,"riscv"    , "SystemV", 7,"return (add,.[],(mul,.[],1000));");
+        testCPU(src,"riscv"    , "SystemV", 9,"return (add,.[],(mul,.[],1000));");
         testCPU(src,"arm"      , "SystemV", 5,"return (add,.[],(mul,.[],1000));");
     }
 
@@ -500,7 +500,7 @@ val sieve = { int N ->
 
         // Evaluate on ARM5 emulator; expect return of an array of primes in
         // the simulated heap.
-        EvalArm64 A5 = TestArm64.build("sieve", src, 100, 105, false);
+        EvalArm64 A5 = TestArm64.build("sieve", src, 100, 88, false);
         int trap_arm = A5.step(10000);
         assertEquals(0, trap_arm);
         int ary_arm = (int)A5.regs[arm.X0];
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/EvalArm64.java b/chapter25/src/test/java/com/seaofnodes/simple/EvalArm64.java
index 86fcf96f..1503adb5 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/EvalArm64.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/EvalArm64.java
@@ -544,10 +544,13 @@ public class EvalArm64 {
                 break;
             }
 
-            case 0xD2: {
+            case 0xD2: // MOVZ
+            case 0xF2: { // MOVK preserves the other halfwords
                 // movz
                 // get immediate
-                rval = (ir >> 5) & 0x7FFF;
+                int shift = ((ir >> 21) & 3)*16;
+                rval = ((ir >> 5) & 0xFFFFL) << shift;
+                if( opcode1==0xF2 ) rval |= regs[rdid] & ~(0xFFFFL << shift);
                 break;
             }
 
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/MemoryEncodingTest.java b/chapter25/src/test/java/com/seaofnodes/simple/MemoryEncodingTest.java
new file mode 100644
index 00000000..2786b403
--- /dev/null
+++ b/chapter25/src/test/java/com/seaofnodes/simple/MemoryEncodingTest.java
@@ -0,0 +1,104 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.codegen.CodeGen;
+import com.seaofnodes.simple.node.*;
+import java.util.BitSet;
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+// Execution regressions are separate from the fixed spill-measurement cohorts.
+public class MemoryEncodingTest {
+    @Test public void testLoopLoadSearch() {
+        String[] sources = {
+            """
+            u8[] !program=new u8[106]; u8[] !out=new u8[0];
+            int sum=0;
+            for(int i=0; i<arg; i++) {
+                sum+=program#;
+                if(i==1) out=new u8[i+1];
+                else if(i==3) out=new u8[2];
+            }
+            return sum+out#;
+            """,
+            // One possibly aliasing arm must reject the unchanged-memory proof.
+            """
+            struct S { int x; }; S !a=new S; S !b=new S;
+            a.x=10; b.x=20; S !p=a; if(arg&1) p=b;
+            int sum=0;
+            for(int i=0; i<6; i++) {
+                if(i==2) p.x=30;
+                else if(i==4) b.x=40;
+                sum+=a.x;
+            }
+            return sum;
+            """,
+            // Unchanged memory does not imply an unchanged loop-carried pointer.
+            """
+            struct S { int x; }; S !a=new S; S !b=new S;
+            a.x=10; b.x=20; S !p=a; int sum=0;
+            for(int i=0; i<6; i++) {
+                if(i==2) a.x=30;
+                sum+=p.x;
+                p=b; if(i&1) p=a;
+            }
+            return sum;
+            """,
+            // All arms fold, but their values differ: build a value Phi.
+            """
+            struct S { int x; }; S !a=new S; a.x=1; int sum=0;
+            for(int i=0; i<6; i++) {
+                sum+=a.x;
+                if(i&1) a.x=2;
+                else if(i==2) a.x=3;
+                else a.x=4;
+            }
+            return sum;
+            """
+        };
+        // Exercise both unresolved Store aliases and nested value-Phi cleanup.
+        for( long seed : new long[]{0,9,126} )
+            for( int p=0; p<sources.length; p++ ) {
+                CodeGen code=new CodeGen(sources[p],seed,true).parse().opto();
+                if( p==0 ) assertNull(code._stop.walk(n ->
+                    n instanceof LoadNode ld && ld.ptr() instanceof ProjNode ptr &&
+                    ptr.in(0) instanceof NewNode nn &&
+                    nn.size()._type==com.seaofnodes.simple.type.TypeInteger.constant(110) ? ld : null));
+                for( int arg=0; arg<7; arg++ ) {
+                    long expected=switch(p) {
+                    case 0 -> 106*arg+(arg>=2 ? 2 : 0);
+                    case 1 -> (arg&1)==0 ? 140 : 60;
+                    case 2 -> 130;
+                    default -> 16;
+                    };
+                    assertEquals(Long.toString(expected),Eval2.eval(code,arg));
+                }
+            }
+    }
+
+    @Test public void testKeepReadsBeforeWrites() {
+        var code = new CodeGen("""
+            struct S { int x; int y; };
+            S !a = new S; S !b = new S;
+            a.x=arg; b.x=arg+1;
+            S !p=a; S !q=b;
+            if (arg<0) { p=b; q=a; }
+            int v;
+            if (arg>1) { v=p.x; p.x=41; p.y=5; }
+            else       { v=q.x; q.x=42; }
+            return v;
+            """).parse().opto();
+        StopNode stop = code._stop;
+        assertEquals(2,countMemoryNodes(stop,LoadNode.class,new BitSet()));
+        assertEquals("-1",Eval2.eval(code,-1));
+        assertEquals("1",Eval2.eval(code,0));
+        assertEquals("3",Eval2.eval(code,3));
+    }
+
+    private static int countMemoryNodes(Node n, Class<?> kind, BitSet seen) {
+        if (n==null || seen.get(n._nid)) return 0;
+        seen.set(n._nid);
+        int cnt=kind.isInstance(n) ? 1 : 0;
+        for (Node def : n._inputs) cnt+=countMemoryNodes(def,kind,seen);
+        return cnt;
+    }
+}
-- 
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