fix lifetime issues with GVN gone wild

3 files changed, 27 insertions, 8 deletions

diff --git a/chapter15/src/main/java/com/seaofnodes/simple/Parser.java b/chapter15/src/main/java/com/seaofnodes/simple/Parser.java
index 728aaca7..4bb18d6b 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/Parser.java
@@ -785,6 +785,7 @@ public class Parser {
         TypeStruct base = tmp._obj;
         int fidx = base.find(name);
         if( fidx == -1 ) throw error("Accessing unknown field '" + name + "' from '" + ptr.str() + "'");
+        expr.keep();
 
         // Get field type and layout offset from base type and field index fidx
         Field f = base._fields[fidx];  // Field from field index
@@ -792,7 +793,8 @@ public class Parser {
         if( name.equals("[]") ) {      // If field is an array body
             // Array index math
             Node idx = require(parseExpression(),"]");
-            off = new AddNode(con(base.aryBase()),new ShlNode(idx,con(base.aryScale())).peephole()).peephole();
+            Node shl = new ShlNode(idx,con(base.aryScale())).peephole();
+            off = new AddNode(con(base.aryBase()),shl).peephole();
         } else {                       // Else normal struct field
             // Hardwired field offset
             off = con(base.offset(fidx));
@@ -802,20 +804,21 @@ public class Parser {
             // Disambiguate "obj.fld==x" boolean test from "obj.fld=x" field assignment
             if( peek('=') ) _lexer._position--;
             else {
+                off.keep();
                 Node val = parseExpression();
                 // Auto-truncate when storing to narrow fields
-                val = zsMask(val,f._type);
-                Node st = new StoreNode(name, f._alias, f._type, memAlias(f._alias), expr, off, val, false);
+                val = zsMask(val,f._type).keep();
+                Node st = new StoreNode(name, f._alias, f._type, memAlias(f._alias), expr.unkeep(), off.unkeep(), val, false);
                 // Arrays include control, as a proxy for a safety range check.
                 // Structs don't need this; they only need a NPE check which is
                 // done via the type system.
                 if( base.isAry() )  st.setDef(0,ctrl());
                 memAlias(f._alias, st.peephole());
-                return val;        // "obj.a = expr" returns the expression while updating memory
+                return val.unkeep(); // "obj.a = expr" returns the expression while updating memory
             }
         }
 
-        Node load = new LoadNode(name, f._alias, f._type.glb(), memAlias(f._alias), expr, off);
+        Node load = new LoadNode(name, f._alias, f._type.glb(), memAlias(f._alias), expr.unkeep(), off);
         // Arrays include control, as a proxy for a safety range check
         // Structs don't need this; they only need a NPE check which is
         // done via the type system.
diff --git a/chapter15/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter15/src/main/java/com/seaofnodes/simple/node/Node.java
index e4b887a0..461f153d 100644
--- a/chapter15/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter15/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -294,7 +294,7 @@ public abstract class Node implements OutNode {
             return this;        // Peephole optimizations turned off
         }
         Node n = peepholeOpt();
-        return n==null ? this : deadCodeElim(n.peephole()); // Cannot return null for no-progress
+        return n==null ? this : deadCodeElim(n.peephole().keep()).unkeep(); // Cannot return null for no-progress
     }
 
     /**
diff --git a/chapter15/src/test/java/com/seaofnodes/simple/Chapter15Test.java b/chapter15/src/test/java/com/seaofnodes/simple/Chapter15Test.java
index 3a379084..6ec7cc1a 100644
--- a/chapter15/src/test/java/com/seaofnodes/simple/Chapter15Test.java
+++ b/chapter15/src/test/java/com/seaofnodes/simple/Chapter15Test.java
@@ -14,8 +14,7 @@ public class Chapter15Test {
 
     @Test
     public void testJig() {
-        Parser parser = new Parser(
-"""
+        Parser parser = new Parser("""
 return 3.14;
 """);
         StopNode stop = parser.parse().iterate();
@@ -24,6 +23,23 @@ return 3.14;
     }
 
     @Test
+    public void testLifetime() {
+        Parser parser = new Parser("""
+u8[] b = new u8[5];
+if (arg) {
+    b[0] = b[0] + 1;
+} else {
+    b[1] = b[1] * 2;
+}
+return b[0] + b[1];
+""");
+        StopNode stop = parser.parse().iterate();
+        assertEquals("return Phi(Region69,1,0);", stop.toString());
+        assertEquals(0L, Evaluator.evaluate(stop,  0));
+        assertEquals(1L, Evaluator.evaluate(stop,  1));
+    }
+
+    @Test
     public void testCyclic() {
         Parser parser = new Parser(
 """