From 628452bb9f6137d433395fae5a9f5d780fb0f1e1 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 10 Aug 2026 15:21:17 -0700
Subject: More hardening

Allow setting random seeds to not fail tests due to e.g. spill-counts or exact graph shapes.
A few missing addDeps or stalling-for-constants fixed.
---
 .../main/java/com/seaofnodes/simple/IterPeeps.java |  5 ++++-
 .../com/seaofnodes/simple/codegen/CodeGen.java     |  8 +++++++-
 .../com/seaofnodes/simple/node/BulkMemPhiNode.java | 23 +++++++++++++++++++++-
 .../java/com/seaofnodes/simple/node/LoadNode.java  | 14 +++++++------
 .../main/java/com/seaofnodes/simple/node/Node.java |  4 ++++
 .../com/seaofnodes/simple/node/ReturnNode.java     |  9 ---------
 .../java/com/seaofnodes/simple/Chapter05Test.java  |  5 ++++-
 .../java/com/seaofnodes/simple/Chapter18Test.java  |  4 +++-
 .../java/com/seaofnodes/simple/Chapter20Test.java  |  2 +-
 .../java/com/seaofnodes/simple/Chapter21Test.java  |  2 +-
 .../java/com/seaofnodes/simple/Chapter22Test.java  |  2 +-
 .../java/com/seaofnodes/simple/Chapter23Test.java  |  2 +-
 .../java/com/seaofnodes/simple/Chapter24Test.java  |  2 +-
 .../test/java/com/seaofnodes/simple/TestArm64.java |  2 +-
 .../src/test/java/com/seaofnodes/simple/TestC.java |  2 +-
 .../test/java/com/seaofnodes/simple/TestRisc5.java |  2 +-
 16 files changed, 60 insertions(+), 28 deletions(-)

(limited to 'chapter25/src')

diff --git a/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java b/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
index 608f368d..9fac7a99 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
@@ -81,11 +81,14 @@ public class IterPeeps {
                     // Everybody gets a free "go again" in case they didn't get
                     // made in their final form.
                     _work.push(x);
+                    // A self-returning peephole can have rewritten its input
+                    // edges.  The new defs gained a user and may have
+                    // backwards, user-sensitive peepholes of their own.
+                    for( Node z : x._inputs ) _work.push(z);
                     // If the result is not self, revisit all inputs (because
                     // there's a new user), and replace in the graph.
                     if( x != n ) {
                         for( Node z : n. _inputs ) _work.push(z);
-                        for( Node z : x. _inputs ) _work.push(z);
                         for( Node z : x._outputs ) _work.push(z);
                         n.subsume(x);
                     }
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java b/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
index 85407ddc..85d8143b 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
@@ -42,6 +42,9 @@ public class CodeGen {
     }
     public Phase _phase;
 
+    /** True when tests deliberately randomize Iter worklist order. */
+    public static boolean iterSeedOverridden() { return System.getProperty("simple.iter.seed") != null; }
+
     // ---------------------------
     // Module Source Root
     public final String _modDir;
@@ -196,7 +199,10 @@ public class CodeGen {
         _phase = null;
         // Start GVN table
         _gvn = new HashMap<>();
-        _iter = new IterPeeps(workListSeed);
+        // Allow whole-suite worklist-order sweeps without rewriting the many
+        // explicit seeds used by tests and command-line compilation.
+        String iterSeed = System.getProperty("simple.iter.seed");
+        _iter = new IterPeeps(iterSeed == null ? workListSeed : Long.parseLong(iterSeed));
         // End points of graph
         _stop = new StopNode().init();
         _start = new StartNode(null,_stop,arg).init();
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 c4a13375..cab85e44 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/BulkMemPhiNode.java
@@ -140,6 +140,7 @@ public class BulkMemPhiNode extends PhiNode {
         return true;
     }
 
+
     // True if the MemMerge has no precise slice still covered by this Phi.
     private boolean canPeek(MemMergeNode mmm) {
         return missingAlias(mmm,false)==0;
@@ -165,7 +166,11 @@ public class BulkMemPhiNode extends PhiNode {
 
     // Return an alias required by a user but still covered by this Phi, or 0.
     private int outputAlias(Node use) {
-        use = addDep(use);      // User alias sharpening changes this decision
+        // This decision depends backwards on an immediate user's alias/set.
+        // Normal graph-neighbor enqueueing flows from defs to uses, so retain
+        // an explicit forward dependency to revisit this Phi when the user
+        // sharpens.
+        use = addDepForwards(use);
         return switch(use) {
         case ScopeNode scope -> 0;
         case ParmNode parm -> 0;
@@ -217,6 +222,11 @@ public class BulkMemPhiNode extends PhiNode {
         for( int i=0; i<nIns(); i++ ) mphi.addDef(in(i));
         Node mem = mphi.peephole();
         assert ((TypeMem)mem._type)._alias==alias;
+        // The precise Phi is a new alias-sensitive user of every memory
+        // input.  Revisit those defs: a predecessor BulkMemPhi may now need
+        // to split this alias even though none of its inputs or types changed.
+        for( int i=1; i<mphi.nIns(); i++ )
+            CodeGen.CODE.add(mphi.in(i));
 
         BitSet aliases = ((BitSet)_aliases.clone());
         aliases.set(alias);
@@ -271,9 +281,20 @@ public class BulkMemPhiNode extends PhiNode {
         if( found==null ) {
             MemPhiNode mphi = new MemPhiNode("$"+alias,alias);
             mphi.addDef(region());
+            // Publishing the Phi on the Region makes it visible to recursive
+            // precisePhi lookups before all loop inputs have been installed.
+            // Give that recursion a valid lattice value until peephole computes
+            // the completed precise-memory Phi.
+            mphi.setType(TypeMem.BOT.makeFrom(alias));
             for( int i=1; i<nIns(); i++ )
                 mphi.addDef(preciseInput(in(i),alias));
             found = mphi.peephole();
+            // A newly reconstructed precise Phi also creates new users of
+            // its memory inputs.  In particular, a BulkMemPhi input may now
+            // need to split this alias, a backwards (user-to-def) change not
+            // covered by processing the new Phi itself.
+            for( int i=1; i<mphi.nIns(); i++ )
+                CodeGen.CODE.add(mphi.in(i));
             CodeGen.CODE.add(found);
         }
         return found;
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 8b8bcaac..f67f2b97 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/LoadNode.java
@@ -317,12 +317,14 @@ public class LoadNode extends MemOpNode {
         int shift = Long.numberOfLeadingZeros(ti._max)-1;
         Node shf = con(shift);
         if( shf._type==TypeInteger.ZERO ) {
-            // Val can be stale and on worklist.  Preserve momnotoncity and bring it up to date
-            if( val._type.isa(_type) )
-                return val;
-            Node val2 = val.peephole();
-            assert val._type.isa(_type);
-            return val2;
+            // A freshly exposed Store value can still be globally unknown.
+            // Revisit this Load when it settles instead of replacing a typed
+            // Load with the weaker transient value.
+            if( !val._type.isa(_type) ) {
+                addDep(val);
+                return null;
+            }
+            return val;
         }
         Node shl = new ShlNode(null,val,shf.keep()).peephole();
         return new SarNode(null,shl,shf.unkeep());
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 986754f4..1ce8382a 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -501,6 +501,10 @@ public abstract class Node implements Cloneable {
             // A high Load through a bad pointer still owns the source error;
             // do not replace it with an unlocated constant before typeCheck.
             !(this instanceof LoadNode && err()!=null) &&
+            // A CallEnd can be temporarily high while optimistic call-graph
+            // linking is still discovering its target Returns.  Its result
+            // projections must remain attached so they can sharpen later.
+            !(this instanceof ProjNode proj && proj.in(0) instanceof CallEndNode && _type.isHigh()) &&
             _type.isHighOrConst() )
             return ConstantNode.make(_type).peephole();
 
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index 93cf1b91..b60d27d7 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -60,15 +60,6 @@ public class ReturnNode extends CFGNode {
         if( ret != fcn.ret() && ret.isa(fcn.ret()) )
             _fun.setSig(fcn.makeFrom(ret));
 
-        // If dead (cannot be reached; infinite loop), kill the exit values
-        if( ctrl()._type==Type.XCONTROL &&
-            !(mem() instanceof ConstantNode && expr() instanceof ConstantNode) ) {
-            Node top = ConstantNode.make(Type.TOP).peephole();
-            setDef(1,top);
-            setDef(2,top);
-            return this;
-        }
-
         return null;
     }
 
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter05Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter05Test.java
index 51ff20ba..6ac08fda 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter05Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter05Test.java
@@ -116,7 +116,10 @@ if( arg==0 )
 return arg+a+b;
 """);
         code.parse().opto();
-        assertEquals("return ((arg+Phi(Region,1,0))+Phi(Region,2,0));", code.print());
+        String ir = code.print();
+        assertTrue(ir,
+                   ir.equals("return ((arg+Phi(Region,1,0))+Phi(Region,2,0));") ||
+                   ir.equals("return (Phi(Region,((!=0)arg+1),0)+Phi(Region,2,0));"));
     }
 
     @Test
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index de332d03..b65e101b 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -145,7 +145,9 @@ return fcn(3);
     public void testFcn5() {
         CodeGen code = new CodeGen("val _fact = { int x -> x <= 1 ? 1 : x*_fact(x-1); }; return _fact(arg);");
         code.parse().opto().typeCheck();
-        assertEquals("Stop[ return Phi(Region,1,(arg*#2)); return Phi(Region,1,(Parm_x(_fact,(arg-1),(x-1))*#2)); ]", code.print());
+        String ir = code.print();
+        assertTrue(ir.equals("Stop[ return Phi(Region,1,(arg*#2)); return Phi(Region,1,(Parm_x(_fact,(arg-1),(x-1))*#2)); ]") ||
+                   ir.equals("Stop[ return Phi(Region,1,(arg*Phi(Region,1,((arg-1)*#2)))); return Phi(Region,1,(Parm_x(_fact,(Sub-1),(x-1))*#2)); ]"));
         assertEquals( "1", Eval2.eval(code, 0));
         assertEquals( "1", Eval2.eval(code, 1));
         assertEquals( "2", Eval2.eval(code, 2));
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
index e4754213..17b0fd0a 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter20Test.java
@@ -19,7 +19,7 @@ public class Chapter20Test {
         code.driver(CodeGen.Phase.RegAlloc,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
         if( stop != null )
             assertEquals(stop, code.print());
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
index a4621165..e4d49e7f 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter21Test.java
@@ -40,7 +40,7 @@ return new _s0.v1;
         CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
         if( stop != null )
             assertEquals(stop, code.print());
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter22Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter22Test.java
index 5a171659..91b8310d 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter22Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter22Test.java
@@ -40,7 +40,7 @@ return new s0.v1;
         CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
         if( stop != null )
             assertEquals(stop, code.print());
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter23Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter23Test.java
index 7e64f226..08acfd32 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter23Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter23Test.java
@@ -25,7 +25,7 @@ public class Chapter23Test {
         CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
         if( stop != null )
             assertEquals(stop, code.print());
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter24Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter24Test.java
index 0f2e1bed..fe8aaf2e 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter24Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter24Test.java
@@ -20,7 +20,7 @@ public class Chapter24Test {
         CodeGen code = new CodeGen(src).driver(CodeGen.Phase.Encoding,cpu,os);
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
         if( stop != null )
             assertEquals(stop, code.print());
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/TestArm64.java b/chapter25/src/test/java/com/seaofnodes/simple/TestArm64.java
index 7394b578..14864d64 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/TestArm64.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/TestArm64.java
@@ -19,7 +19,7 @@ public class TestArm64 {
         // Allocation quality not degraded
         int delta = spills>>3;
         if( delta == 0 ) delta =1;
-        if( spills != -1 ) assertEquals("Expect spills:", spills, code._regAlloc._spillScaled, delta);
+        if( spills != -1 && !CodeGen.iterSeedOverridden() ) assertEquals("Expect spills:", spills, code._regAlloc._spillScaled, delta);
 
         // Image
         byte[] image = new byte[1<<20]; // A megabyte (1024*1024 bytes)
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/TestC.java b/chapter25/src/test/java/com/seaofnodes/simple/TestC.java
index 5c49d3a8..7177f765 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/TestC.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/TestC.java
@@ -99,7 +99,7 @@ public abstract class TestC {
         // Allocation quality not degraded
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
     }
 
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/TestRisc5.java b/chapter25/src/test/java/com/seaofnodes/simple/TestRisc5.java
index aff95c38..658909ca 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/TestRisc5.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/TestRisc5.java
@@ -19,7 +19,7 @@ public abstract class TestRisc5 {
         // Allocation quality not degraded
         int delta = spills>>3;
         if( delta==0 ) delta = 1;
-        if( spills != -1 )
+        if( spills != -1 && !CodeGen.iterSeedOverridden() )
             assertEquals("Expect spills:",spills,code._regAlloc._spillScaled,delta);
 
         // Image
-- 
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