Ch20 reg

.gitignore

@@ -1,6 +1,7 @@
 # Java stuff
 # Compiled class file
 *.class
+build/
 
 # Log file
 *.log

README.md

@@ -29,32 +29,38 @@ the backend starts with levering Java: the Evaluator (first appears in Chapter
 
 The following is a rough plan, subject to change.
 
-Each chapter will be self-sufficient and complete; in the sense that each chapter will fully implement
-a subset of the Simple language, and include everything that was created in the previous chapter.
-Each chapter will also include a detailed commentary on relevant aspects of the
-Sea Of Nodes intermediate representation.
+Each chapter will be self-sufficient and complete; in the sense that each
+chapter will fully implement a subset of the Simple language, and include
+everything that was created in the previous chapter.  Each chapter will also
+include a detailed commentary on relevant aspects of the Sea Of Nodes
+intermediate representation.
 
-The Simple language will be styled after a subset of C or Java
+The Simple language is styled after a subset of C or Java.
 
 * [Chapter 1](chapter01/README.md): Script that returns an integer literal, i.e., an empty function that takes no arguments and returns a single integer value. The `return` statement.
 * [Chapter 2](chapter02/README.md): Simple binary arithmetic such as addition, subtraction, multiplication, division
   with constants. Peephole optimization / simple constant folding.
 * [Chapter 3](chapter03/README.md): Local variables, and assignment statements. Read on RHS, SSA, more peephole optimization if local is a
   constant.
-* [Chapter 4](chapter04/README.md): A non-constant external variable input named `arg`. Binary and Comparison operators involving constants and `arg`. Non-zero values will be truthy. Peephole optimizations involving algebraic simplifications.
+* [Chapter 4](chapter04/README.md): A non-constant external variable input
+  named `arg`.  Binary and Comparison operators involving constants and `arg`.
+  Non-zero values will be truthy.  Peephole optimizations involving algebraic
+  simplifications.
 * [Chapter 5](chapter05/README.md): `if` statement. CFG construction.
 * [Chapter 6](chapter06/README.md): Peephole optimization around dead control flow.
-* [Chapter 7](chapter07/README.md): `while` statement. Looping construct - eager phi approach.
-* [Chapter 8](chapter08/README.md): Looping construct continued, lazy phi creation, `break` and `continue` statements.
+* [Chapter 7](chapter07/README.md): `while` statement; looping constructs - eager phi approach.
+* [Chapter 8](chapter08/README.md): Looping constructs continued, lazy phi creation, `break` and `continue` statements.
 * [Chapter 9](chapter09/README.md): Global Value Numbering. Iterative peepholes to fixpoint. Worklists.
-* [Chapter 10](chapter10/README.md): User defined Struct types. Memory effects: general memory edges in SSA. Equivalence class aliasing. Null pointer analysis. Peephole optimization around load-after-store/store-after-store.
+* [Chapter 10](chapter10/README.md): User defined Struct types. Memory effects:
+  general memory edges in SSA.  Equivalence class aliasing.  Null pointer
+  analysis.  Peephole optimization around load-after-store/store-after-store.
 * [Chapter 11](chapter11/README.md): Global Code Motion - Scheduling.
 * [Chapter 12](chapter12/README.md): Float type.
 * [Chapter 13](chapter13/README.md): Nested references in Structs.
 * [Chapter 14](chapter14/README.md): Narrow primitive types (e.g. bytes)
 * [Chapter 15](chapter15/README.md): One dimensional static length array type, with array loads and stores.
 * [Chapter 16](chapter16/README.md): Constructors
-* [Chapter 17](chapter17/README.md): Mutability & Syntax Sugar: `var`, `val`, `x+=y`, `for(init;test;next)body`
+* [Chapter 17](chapter17/README.md): Mutability & Syntax Sugar: `var`, `val`, `x+=y`, `for(init; test; next) body`
 * [Chapter 18](chapter18/README.md): Functions and calls.
 * [Chapter 19](chapter19/README.md): Instruction selection and portable compilation
 * [Chapter 20](chapter20/README.md): Graph Coloring Register Allocation

chapter02/README.md

@@ -42,6 +42,18 @@ We extend the set of nodes by adding following additional node types.
 | Div       | Data | Divide a value by another     | Two data nodes, values are divided, order matters          | Result of the division      |
 | Minus     | Data | Negate a value                | One data node, value is negated                            | Result of the unary minus   |
 
+
+## *Value* equality vs *Reference* equality
+
+In much of Simple, Nodes are looked up (`find()` calls) via *reference*
+equality.  This is by far the most common case.  In [Chapter
+9](../chapter09/README.md) we introduce *value* equality for the first time.
+In both cases the choice of value-vs-reference equality is intentional: it is
+*never* correct to "just pick one or the other kind of equality".  When in
+doubt check the context: only *Global Value Numbering* uses value equality;
+everywhere we mean reference equality.
+
+
 ## Peephole Optimizations
 
 Nodes in the graph can be peephole-optimized.  The graph is viewed through a
@@ -141,6 +153,7 @@ starting in [Chapter 4](../chapter04/README.md) and [Chapter
 There are other important properties of the Lattice that we discuss in [Chapter
 4](../chapter04/README.md) and [Chapter 10](../chapter10/README.md), such as the "meet" and "join" operators and their rules.
 
+
 ## Nodes Pre Peephole Optimization
 
 The following visual shows how the graph looks like pre-peephole optimization:
@@ -152,10 +165,12 @@ The following visual shows how the graph looks like pre-peephole optimization:
 * The edges from Constants to Start are shown in dotted lines as these are not true control edges
 * We label each edge with its position in the node's list of inputs.
 
+
 ## Post-peephole
 
 ![Example Visual](./docs/02-post-peephole-ex1.svg)
 
+
 ## Demonstration
 To demonstrate how the optimisation works, let's consider the following code:
 ```

chapter09/README.md

@@ -48,6 +48,14 @@ get the same result - and can be shared.
   constant 17 is not the same as 99, but both are the same `ConstantNode` class
   and label.  The `eq` and `hash` calls check (or hash) these extra bits.
 
+Note the intentional *value* equality here.  In many places in Simple we use
+*reference* equality - e.g. node/edge maintenance is via reference equality, not
+value equality, so e.g. the `Utils.find()` call finds via reference.  Through
+out the Simple project whenever a Node lookup is happening, beware if its via
+*value* or *reference* equality; this is not always explicitly called out but
+should be obvious from context.
+
+
 Since we edit the graph a lot, Nodes can have their inputs change which changes
 their hash which means they can't be found in the GVN table.  E.g. we swap out
 the `Add` for a `Con` in:

chapter13/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -173,4 +173,9 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter13/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -55,4 +55,9 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter13/src/test/java/com/seaofnodes/simple/Chapter13Test.java

@@ -130,6 +130,19 @@ public void testNullRef3() {
         catch( Exception e ) { assertEquals("Cannot store 3.14 into field IntBot i",e.getMessage()); }
     }
 
+    @Test
+    public void testNullRef4() {
+        Parser parser = new Parser("-null-5/null-5");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Expected an identifier, found 'null'",e.getMessage()); }
+    }
+
+    @Test public void testNullRef5() {
+        Parser parser = new Parser("return null+42;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
     @Test
     public void testEmpty() {
         Parser parser = new Parser(

chapter14/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -183,4 +183,9 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter14/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -58,4 +58,9 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter14/src/test/java/com/seaofnodes/simple/Chapter13Test.java

@@ -130,6 +130,19 @@ public void testNullRef3() {
         catch( Exception e ) { assertEquals("Cannot store 3.14 into field int i",e.getMessage()); }
     }
 
+    @Test
+    public void testNullRef4() {
+        Parser parser = new Parser("-null-5/null-5");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Expected an identifier, found 'null'",e.getMessage()); }
+    }
+
+    @Test public void testNullRef5() {
+        Parser parser = new Parser("return null+42;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
     @Test
     public void testEmpty() {
         Parser parser = new Parser(

chapter15/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -184,4 +184,9 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter15/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -58,4 +58,9 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter15/src/test/java/com/seaofnodes/simple/Chapter13Test.java

@@ -130,6 +130,19 @@ public void testNullRef3() {
         catch( Exception e ) { assertEquals("Cannot store 3.14 into field int i",e.getMessage()); }
     }
 
+    @Test
+    public void testNullRef4() {
+        Parser parser = new Parser("-null-5/null-5");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Expected an identifier, found 'null'",e.getMessage()); }
+    }
+
+    @Test public void testNullRef5() {
+        Parser parser = new Parser("return null+42;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
     @Test
     public void testEmpty() {
         Parser parser = new Parser(

chapter16/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -184,4 +184,9 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter16/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -60,4 +60,9 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter16/src/test/java/com/seaofnodes/simple/Chapter13Test.java

@@ -129,6 +129,19 @@ public void testNullRef3() {
         catch( Exception e ) { assertEquals("Cannot store 3.14 into field int i",e.getMessage()); }
     }
 
+    @Test
+    public void testNullRef4() {
+        Parser parser = new Parser("-null-5/null-5");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Expected an identifier, found 'null'",e.getMessage()); }
+    }
+
+    @Test public void testNullRef5() {
+        Parser parser = new Parser("return null+42;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
     @Test
     public void testEmpty() {
         Parser parser = new Parser(

chapter17/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -44,6 +44,7 @@ static boolean overflow( long x, long y ) {
     public Node idealize () {
         Node lhs = in(1);
         Node rhs = in(2);
+        if( rhs.err() != null ) return null;
         Type t2 = rhs._type;
 
         // Add of 0.  We do not check for (0+x) because this will already
@@ -184,4 +185,9 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter17/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -60,4 +60,9 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public String err() {
+        if( !(in(1)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(1)._type;
+        if( !(in(2)._type instanceof TypeInteger) ) return "Cannot '"+label()+"' " + in(2)._type;
+        return null;
+    }
 }

chapter17/src/test/java/com/seaofnodes/simple/Chapter13Test.java

@@ -129,6 +129,19 @@ public void testNullRef3() {
         catch( Exception e ) { assertEquals("Type 3.14 is not of declared type int",e.getMessage()); }
     }
 
+    @Test
+    public void testNullRef4() {
+        Parser parser = new Parser("-null-5/null-5;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
+    @Test public void testNullRef5() {
+        Parser parser = new Parser("return null+42;");
+        try { parser.parse().iterate(); fail(); }
+        catch( Exception e ) { assertEquals("Cannot 'Add' null",e.getMessage()); }
+    }
+
     @Test
     public void testEmpty() {
         Parser parser = new Parser(

chapter17/src/test/java/com/seaofnodes/simple/Chapter17Test.java

@@ -11,12 +11,7 @@ public class Chapter17Test {
 
     @Test
     public void testJig() {
-        Parser parser = new Parser("""
-int i = 0;
-i=i=1;
-return i;
-                                   //return 3.14;
-""");
+        Parser parser = new Parser("return 1;");
         StopNode stop = parser.parse().iterate();
         assertEquals("return 1;", stop.toString());
         assertEquals(1L, Evaluator.evaluate(stop,  0));

chapter18/src/main/java/com/seaofnodes/simple/Parser.java

@@ -1725,6 +1725,6 @@ public static class ParseException extends RuntimeException {
         public final Lexer _loc;
         // file:line:charoff err
         //String msg = "src:"+_line_number+":"+(_position-_line_start)+" "+errorMessage;
-        ParseException( String msg, Lexer loc ) { super(msg);  _loc = loc; assert loc!=null; }
+        ParseException( String msg, Lexer loc ) { super(msg);  _loc = loc; }
     }
 }

chapter18/src/main/java/com/seaofnodes/simple/node/AddNode.java

@@ -1,7 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.*;
-
 import java.util.BitSet;
 
 public class AddNode extends Node {
@@ -44,6 +44,7 @@ static boolean overflow( long x, long y ) {
     public Node idealize () {
         Node lhs = in(1);
         Node rhs = in(2);
+        if( rhs.err()!=null ) return null;
         Type t2 = rhs._type;
 
         // Add of 0.  We do not check for (0+x) because this will already
@@ -184,4 +185,10 @@ static boolean spine_cmp( Node hi, Node lo, Node dep ) {
 
     @Override Node copy(Node lhs, Node rhs) { return new AddNode(lhs,rhs); }
     @Override Node copyF() { return new AddFNode(null,null); }
+    @Override public Parser.ParseException err() {
+        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
+        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(1)._type,null);
+        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(2)._type,null);
+        return null;
+    }
 }

chapter18/src/main/java/com/seaofnodes/simple/node/MulNode.java

@@ -1,8 +1,8 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
-
 import java.util.BitSet;
 
 public class MulNode extends Node {
@@ -60,4 +60,10 @@ public Node idealize() {
     }
     @Override Node copy(Node lhs, Node rhs) { return new MulNode(lhs,rhs); }
     @Override Node copyF() { return new MulFNode(null,null); }
+    @Override public Parser.ParseException err() {
+        if( in(1)._type.isHigh() || in(2)._type.isHigh() ) return null;
+        if( !(in(1)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(1)._type,null);
+        if( !(in(2)._type instanceof TypeInteger) ) return Parser.error("Cannot '"+label()+"' " + in(2)._type,null);
+        return null;
+    }
 }