From 69e4a21f71aca4954469063387063434af35e679 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Sun, 25 Oct 2026 10:24:58 -0700
Subject: Backport a few missing guard checks

---
 .../main/java/com/seaofnodes/simple/node/LoadNode.java  | 16 ++++++++++++++--
 .../java/com/seaofnodes/simple/ConstructionTest.java    | 17 +++++++++++++++++
 .../java/com/seaofnodes/simple/IncompleteTypesTest.java | 13 +++++++++++++
 3 files changed, 44 insertions(+), 2 deletions(-)

(limited to 'chapter26/src')

diff --git a/chapter26/src/main/java/com/seaofnodes/simple/node/LoadNode.java b/chapter26/src/main/java/com/seaofnodes/simple/node/LoadNode.java
index b9dd2af6..736d91a2 100644
--- a/chapter26/src/main/java/com/seaofnodes/simple/node/LoadNode.java
+++ b/chapter26/src/main/java/com/seaofnodes/simple/node/LoadNode.java
@@ -208,7 +208,12 @@ public class LoadNode extends MemOpNode {
                 // skipping it can make a compound assignment read the old value.
                 if( st._alias==1 ) return null;
                 addDep(st.ptr());
-                if( _alias==st._alias && ptr==address(st.ptr()) && off()==st.off() ) return st;
+                if( _alias==st._alias && ptr==address(st.ptr()) && 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( _alias==st._alias && !neverAlias(ptr,address(st.ptr())) &&
                     !addDep(off())._type.join(addDep(st.off())._type).isHigh() ) return null;
                 mem=st.mem();
@@ -313,8 +318,15 @@ public class LoadNode extends MemOpNode {
         // Signed extension
         int shift = Long.numberOfLeadingZeros(ti._max)-1;
         Node shf = con(shift);
-        if( shf._type==TypeInteger.ZERO )
+        if( shf._type==TypeInteger.ZERO ) {
+            // A constructor's loop Phi may still have an unsettled type.
+            // Wait for it instead of weakening the typed Load's users.
+            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/chapter26/src/test/java/com/seaofnodes/simple/ConstructionTest.java b/chapter26/src/test/java/com/seaofnodes/simple/ConstructionTest.java
index dd20b746..a3317d09 100644
--- a/chapter26/src/test/java/com/seaofnodes/simple/ConstructionTest.java
+++ b/chapter26/src/test/java/com/seaofnodes/simple/ConstructionTest.java
@@ -7,6 +7,23 @@ import org.junit.Test;
 import static org.junit.Assert.*;
 
 public class ConstructionTest {
+    @Test public void testConditionalConstructorLoop() {
+        String[] bodies = {
+            "while(n--) if(n) x=1;",
+            "for(int i=0;i<n;i++) { if(i==1) continue; if(i==3) break; x+=i+1; }"
+        };
+        int[][] expected = {{0,0,1,1,1,1}, {0,1,1,4,4,4}};
+        for( int i=0; i<bodies.length; i++ )
+            for( long seed : new long[]{123,456,789} ) {
+                String src = "struct C { int x; new C={int n -> "+bodies[i]+"}; }; return new C(arg).x;";
+                var code = new CodeGen(src,com.seaofnodes.simple.type.TypeInteger.BOT,seed,true)
+                    .driver(CodeGen.Phase.TypeCheck);
+                for( int arg=0; arg<expected[i].length; arg++ )
+                    assertEquals("case="+i+" seed="+seed+" arg="+arg,
+                        Integer.toString(expected[i][arg]),Eval2.eval(code,arg));
+            }
+    }
+
     private static final String CONSTRUCT = """
         struct Box {
             int x=7;
diff --git a/chapter26/src/test/java/com/seaofnodes/simple/IncompleteTypesTest.java b/chapter26/src/test/java/com/seaofnodes/simple/IncompleteTypesTest.java
index f2f7d882..419cac51 100644
--- a/chapter26/src/test/java/com/seaofnodes/simple/IncompleteTypesTest.java
+++ b/chapter26/src/test/java/com/seaofnodes/simple/IncompleteTypesTest.java
@@ -6,6 +6,19 @@ import com.seaofnodes.simple.type.TypeInteger;
 import static org.junit.Assert.assertEquals;
 
 public class IncompleteTypesTest {
+    @Test public void testLoadFromUnsettledLoopPhi() {
+        String src = """
+            struct C { int x; };
+            val f={int n -> return new C { while(n--) if(n) x=1; }; };
+            return f(arg).x;
+            """;
+        for( long seed : new long[]{123,456,789} ) {
+            var code = new CodeGen(src,TypeInteger.BOT,seed,true).driver(CodeGen.Phase.TypeCheck);
+            for( int arg=0; arg<6; arg++ )
+                assertEquals("seed="+seed+" arg="+arg,arg<2 ? "0" : "1",Eval2.eval(code,arg));
+        }
+    }
+
     @Test public void testForwardFieldAndNumericMode() {
         // At the addition, neither the field's type nor its offset is known.
         String src = """
-- 
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