From 514b3147bf08817d17aacc492be255621209ec8b Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Wed, 7 Oct 2026 12:37:06 -0700
Subject: RoundF32 actually rounds

---
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/type/TypeStruct.java     |  2 +-
 .../java/com/seaofnodes/simple/Chapter18Test.java  | 27 ++++++++++++++++++++++
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 .../com/seaofnodes/simple/node/RoundF32Node.java   |  1 +
 docs/chapter-backports.md                          | 26 ++++++++++++++++-----
 16 files changed, 61 insertions(+), 7 deletions(-)

diff --git a/chapter14/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter14/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..6be071a2 100644
--- a/chapter14/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter14/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.BOT ) return TypeFloat.B32;
         return in(1)._type;
     }
 
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter15/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..6be071a2 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.BOT ) return TypeFloat.B32;
         return in(1)._type;
     }
 
diff --git a/chapter16/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter16/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..6be071a2 100644
--- a/chapter16/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter16/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.BOT ) return TypeFloat.B32;
         return in(1)._type;
     }
 
diff --git a/chapter17a/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter17a/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..6be071a2 100644
--- a/chapter17a/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter17a/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.BOT ) return TypeFloat.B32;
         return in(1)._type;
     }
 
diff --git a/chapter17b/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter17b/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..6be071a2 100644
--- a/chapter17b/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter17b/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.BOT ) return TypeFloat.B32;
         return in(1)._type;
     }
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter18/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
index bc640955..fff6a7db 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/type/TypeStruct.java
@@ -49,7 +49,7 @@ public class TypeStruct extends Type {
 
     // Array
     public static TypeStruct makeAry(TypeInteger len, int lenAlias, Type body, int bodyAlias) {
-        assert body instanceof TypeInteger || (body instanceof TypeNil tn && tn.nullable());
+        assert body instanceof TypeInteger || body instanceof TypeFloat || (body instanceof TypeNil tn && tn.nullable());
         return make("[" + body.str() + "]",
                     Field.make("#" ,len , lenAlias,true ),
                     Field.make("[]",body,bodyAlias,false));
diff --git a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index c4d5b9ac..0758fbf5 100644
--- a/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/chapter18/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -9,6 +9,33 @@ import static org.junit.Assert.fail;
 import org.junit.Ignore;
 
 public class Chapter18Test {
+    @Test public void testFloatArrays() {
+        for( String type : new String[]{"flt","f64","f32"} ) {
+            CodeGen zero = new CodeGen("var a = new "+type+"[arg]; return a[arg-1];")
+                .parse().opto().typeCheck();
+            assertEquals("0.0",Eval2.eval(zero,3));
+            // Eval2 does not execute RoundF32 yet; check nonconstant narrowing here.
+            new CodeGen(type+" x = arg; var a = new "+type+"[arg]; a[0] = x; return a[0];")
+                .parse().opto().typeCheck();
+        }
+        for( String type : new String[]{"flt","f64"} ) {
+            CodeGen loop = new CodeGen("var a = new "+type+"[arg]; "+
+                "for(int i=0; i<arg; i++) a[i] += i+0.25; return a[0]+a[arg-1];")
+                .parse().opto().typeCheck();
+            assertEquals("0.5",Eval2.eval(loop,1));
+            assertEquals("3.5",Eval2.eval(loop,4));
+
+            CodeGen rounded = new CodeGen("var a = new "+type+"[arg]; "+
+                "for(int i=0; i<arg; i++) a[i] = 16777216.0+i; return a[arg-1];")
+                .parse().opto().typeCheck();
+            assertEquals("1.6777217E7",Eval2.eval(rounded,2));
+        }
+        CodeGen rounded = new CodeGen("var a = new f32[arg]; "+
+            "for(int i=0; i<arg; i++) a[i] = 16777217.0; return a[arg-1];")
+            .parse().opto().typeCheck();
+        assertEquals("1.6777216E7",Eval2.eval(rounded,2));
+    }
+
     @Test public void testNeverExitLoopDepth() {
         String[] sources = {
             "if(arg) while(1) {} return 7;",
diff --git a/chapter19/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter19/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter19/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter19/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter20/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter20/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter20/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter20/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter21/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter21/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter21/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter21/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter22/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter22/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter22/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter22/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter23/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter23/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter23/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter23/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter24/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter24/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 78e7698c..10a0e4aa 100644
--- a/chapter24/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter24/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -16,6 +16,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java b/chapter25/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
index 1a3592dc..65f10a79 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/RoundF32Node.java
@@ -15,6 +15,7 @@ public class RoundF32Node extends Node {
     public Type compute() {
         if (in(1)._type instanceof TypeFloat i0 && i0.isConstant() )
             return TypeFloat.constant((float)i0.value());
+        if( in(1)._type==TypeFloat.F64 ) return TypeFloat.F32;
         return in(1)._type;
     }
 
diff --git a/docs/chapter-backports.md b/docs/chapter-backports.md
index e909e573..765cad82 100644
--- a/docs/chapter-backports.md
+++ b/docs/chapter-backports.md
@@ -473,12 +473,6 @@ lines beyond the original extraction.
   Cover constant folding, evaluation, and machine lowering on all three targets;
   update the Chapter 14 explanation and add boundary-case regressions.
 
-- **Existing Chapter 18 floating-array assertion.** The unchanged
-  `TypeStruct.makeAry` assertion accepts integers and nullable references but
-  excludes TypeFloat; `return new flt[1];` fails under `-ea`. The Chapter 18
-  memory probe uses floating struct fields for initialization coverage instead.
-  Investigate separately; this port does not change the array type lattice.
-
 - **Chapter 24 Load BOTTOM-on-error backport, unwound/deferred (2026-09-28).**
   Cliff requested starting with 24 and analyzing failures before proceeding.
   Literal global BOTTOM memory/pointer inputs already propagate BOTTOM. The
@@ -670,6 +664,26 @@ The top-level runner accepts explicit chapter lists, e.g.
 
 ## Validation record
 
+- **Floating arrays in Chapter 18 (2026-10-07).** Added TypeFloat to the
+  `TypeStruct.makeAry` assertion, matching Chapter 19 onward; earlier array
+  chapters already accept floating elements. The original `return new flt[1];`
+  reproduction passes with assertions enabled. One regression covers flt/f64/f32
+  zero initialization, flt/f64 looped loads and stores, and constant f32 rounding.
+  It fails at the original assertion before the correction. The complete
+  Chapter 18 suite passes (340 tests plus its fuzzer wrapper); no other compiler
+  snapshot needed this assertion change. Nonconstant scalar and array narrowing
+  now passes type checking with the RoundF32 correction below. Eval2 does not
+  execute RoundF32 yet, so runtime coverage uses constant f32 stores. Logs:
+  `build/float-arrays-18-before.log`, `build/float-arrays-18-after.log`.
+
+- **Nonconstant f32 narrowing (2026-10-07).** RoundF32Node now returns F32
+  for an F64 input in Chapters 18-25, and the equivalent B32 for BOT in
+  Chapters 14-17b. Constant rounding and other input types are unchanged.
+  Chapter 18's floating-array regression also checks nonconstant scalar and
+  array assignments. Complete Make suites pass in every affected chapter,
+  including Chapter 25's native tests; no expected graph or allocation results
+  changed. Logs: `build/round-f32-<chapter>.log`.
+
 - **Shared Phi inputs and deterministic inlining (2026-10-07).** Chapters
   20-25 split a self-conflicting Phi's inputs when another Phi shares them;
   splitting only the entry and result could leave two loop Phis joined through
-- 
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