Support post ++ on arrays and structs

3 files changed, 67 insertions, 14 deletions

diff --git a/chapter17/src/main/java/com/seaofnodes/simple/Parser.java b/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
index 9710be30..abd70f89 100644
--- a/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter17/src/main/java/com/seaofnodes/simple/Parser.java
@@ -761,8 +761,8 @@ public class Parser {
         // Expect an identifier now
         ScopeMinNode.Var n = requireLookupId("an identifier or expression");
         Node rvalue = _scope.in(n).keep();
-        if( matchx("++") ) _scope.update(n,new AddNode(rvalue,con( 1)).peephole());
-        if( matchx("--") ) _scope.update(n,new AddNode(rvalue,con(-1)).peephole());
+        if( matchx("++") || matchx("--") )
+            _scope.update(n,new AddNode(rvalue,con( _lexer.peek(-1)=='+' ? 1 : -1)).peephole());
         return rvalue.unkeep();
     }
 
@@ -907,24 +907,24 @@ public class Parser {
         // Get field type and layout offset from base type and field index fidx
         Field f = base._fields[fidx];  // Field from field index
 
-        Node off = name.equals("[]")       // If field is an array body
+        Node off = (name.equals("[]")       // If field is an array body
             // Array index math
             ? new AddNode(con(base.aryBase()),new ShlNode(require(parseExpression(),"]"),con(base.aryScale())).peephole()).peephole()
             // Struct field offsets are hardwired
-            : con(base.offset(fidx));
+            : con(base.offset(fidx))).keep();
 
         // Disambiguate "obj.fld==x" boolean test from "obj.fld=x" field assignment
         if( matchOpx('=','=') ) {
             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, 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);
@@ -932,7 +932,23 @@ public class Parser {
         // Structs don't need this; they only need a NPE check which is
         // done via the type system.
         if( base.isAry() ) load.setDef(0,ctrl());
-        return parsePostfix(load.peephole());
+        load = load.peephole();
+
+        // ary[idx]++
+        if( matchx("++") || matchx("--") ) {
+            Node inc = new AddNode(load,con( _lexer.peek(-1)=='+' ? 1 : -1)).peephole();
+            Node val = zsMask(inc,f._type);
+            Node st = new StoreNode(name, f._alias, f._type, memAlias(f._alias), expr, off, 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());
+            // And use the original loaded value as the result
+        }
+        if( off.unkeep().isDead() ) off.kill();
+
+        return parsePostfix(load);
     }
 
 
@@ -1044,6 +1060,8 @@ public class Parser {
             return isEOF() ? Character.MAX_VALUE   // Special value that causes parsing to terminate
                     : (char) _input[_position];
         }
+        // Just crash if misused
+        public byte peek(int off) { return _input[_position+off]; }
 
         private char nextChar() {
             char ch = peek();
diff --git a/chapter17/src/test/java/com/seaofnodes/simple/BrainFuckTest.java b/chapter17/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
index 0a48d2e7..88dccc49 100644
--- a/chapter17/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
+++ b/chapter17/src/test/java/com/seaofnodes/simple/BrainFuckTest.java
@@ -23,10 +23,8 @@ public class BrainFuckTest {
 
         Parser parser = new Parser(
                 encoded + """
-int pc = 0;
-int d = 0;
-u8[] data = new u8[100];
-u8[] output = new u8[0];
+int pc = 0, d = 0;
+u8[] data = new u8[100],  output = new u8[0];
 
 while (pc < program#) {
     int command = program[pc];
@@ -35,9 +33,9 @@ while (pc < program#) {
     } else if (command == 60) {
         d--;
     } else if (command == 43) {
-        data[d] = data[d] + 1;
+        data[d]++;
     } else if (command == 45) {
-        data[d] = data[d] - 1;
+        data[d]--;
     } else if (command == 46) {
         u8[] old = output;
         output = new u8[output# + 1];
diff --git a/chapter17/src/test/java/com/seaofnodes/simple/Chapter17Test.java b/chapter17/src/test/java/com/seaofnodes/simple/Chapter17Test.java
index 91c275ce..45e3ef0f 100644
--- a/chapter17/src/test/java/com/seaofnodes/simple/Chapter17Test.java
+++ b/chapter17/src/test/java/com/seaofnodes/simple/Chapter17Test.java
@@ -49,6 +49,43 @@ return -arg---arg--;
         assertEquals(1L, Evaluator.evaluate(stop, 0));
     }
 
+    @Test
+    public void testInc3() {
+        Parser parser = new Parser("""
+int[] xs = new int[arg];
+xs[0]++;
+xs[1]++;
+return xs[0];
+""");
+        StopNode stop = parser.parse().iterate();
+        assertEquals("return 1;", stop.toString());
+        assertEquals(1L, Evaluator.evaluate(stop, 2));
+    }
+
+    @Test
+    public void testInc4() {
+        Parser parser = new Parser("""
+u8[] xs = new u8[1];
+xs[0]--;
+return xs[0];
+""");
+        StopNode stop = parser.parse().iterate();
+        assertEquals("return 255;", stop.toString());
+        assertEquals(255L, Evaluator.evaluate(stop, 2));
+    }
+
+    @Test
+    public void testInc5() {
+        Parser parser = new Parser("""
+struct S { u16 x; };
+S s = new S;
+s.x--;
+return s.x;
+""");
+        StopNode stop = parser.parse().iterate();
+        assertEquals("return 65535;", stop.toString());
+        assertEquals(65535L, Evaluator.evaluate(stop, 2));
+    }
 
     @Test
     public void testLinkedList2() {