Squashed commit of the following:

commit a00bfc643e834498b020eb47ee37da4a17cf6e39
Author: Cliff Click <cliffc@acm.org>
Date:   Thu Aug 20 12:27:52 2026 -0700

    Add a emacs Simple.el mode

commit b5b399e16038d20ba6928aa329268b229b90e2f7
Author: Cliff Click <cliffc@acm.org>
Date:   Thu Aug 20 11:37:17 2026 -0700

    Tone down expensive asserts

    Put the expensive asserts on a log-scale flag, run them only once every 2^N attempts

21 files changed, 86 insertions, 47 deletions

diff --git a/.dir-locals.el b/.dir-locals.el
index 1a9cb5e1..74fde018 100644
--- a/.dir-locals.el
+++ b/.dir-locals.el
@@ -2,5 +2,5 @@
 ;;; For more information see (info "(emacs) Directory Variables")
 (
  (dired-mode . ((c-basic-offset . 4)))
- (java-mode  . ((c-basic-offset . 4) (eval . (set-buffer-file-coding-system 'unix))) )
+ (java-mode  . ((c-basic-offset . 4)))
 )
diff --git a/.emacs/simple-mode.el b/.emacs/simple-mode.el
new file mode 100644
index 00000000..47800806
--- /dev/null
+++ b/.emacs/simple-mode.el
@@ -0,0 +1,38 @@
+;;; simple-mode.el --- Major mode for Simple source files -*- lexical-binding: t; -*-
+
+(require 'cc-mode)
+
+(defconst simple-mode-primitive-types
+  '("int" "i8" "i16" "i32" "i64" "u8" "u16" "u32" "u64"
+    "byte" "bool" "flt" "f32" "f64" "val" "var")
+  "Primitive and built-in type names in Simple.")
+
+(defconst simple-mode-font-lock-keywords
+  `((,(regexp-opt simple-mode-primitive-types 'symbols) . font-lock-type-face)
+    (,(regexp-opt '("boolean" "long" "short" "char" "float" "double" "void") 'symbols) (0 nil t))
+    ("\\_<new\\_>\\s-+\\(?:[[:alpha:]_][[:alnum:]_$]*\\.\\)*\\([[:alpha:]_][[:alnum:]_$]*\\)" (1 nil t)))
+  "Additional Simple keywords using Java's type face.")
+
+(defun simple-mode-set-indentation ()
+  (setq-local c-basic-offset 4)
+  (setq-local indent-tabs-mode nil))
+
+(define-derived-mode simple-mode java-mode "Simple"
+  "Major mode for Simple .smp source files."
+  (simple-mode-set-indentation)
+  (setq-local c-primitive-type-key
+              (concat "\\(" (regexp-opt simple-mode-primitive-types) "\\)"
+                      "\\([^[:alnum:]_$]\\|$\\)"))
+  (setq-local font-lock-defaults
+              `((,@java-font-lock-keywords ,@simple-mode-font-lock-keywords)
+                nil nil ((?_ . "w") (?$ . "w"))
+                c-beginning-of-syntax
+                (font-lock-mark-block-function . c-mark-function)))
+  (setq-local font-lock-keywords nil)
+  (font-lock-set-defaults)
+  (font-lock-mode 1))
+
+(add-hook 'simple-mode-hook #'simple-mode-set-indentation)
+
+(provide 'simple-mode)
+;;; simple-mode.el ends here
diff --git a/chapter25/docs/examples/A_helloWorld.smp b/chapter25/docs/examples/A_helloWorld.smp
index ac399661..4ed6abdf 100644
--- a/chapter25/docs/examples/A_helloWorld.smp
+++ b/chapter25/docs/examples/A_helloWorld.smp
@@ -1,3 +1,2 @@
-// -*- mode: java;  -*-
 sys.io.p("Hello, World!\n");
 return 0;
diff --git a/chapter25/docs/examples/BubbleSort.smp b/chapter25/docs/examples/BubbleSort.smp
index 7327e461..ef92c29e 100644
--- a/chapter25/docs/examples/BubbleSort.smp
+++ b/chapter25/docs/examples/BubbleSort.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // An implementation of
 // https://sampleprograms.io/projects/bubble-sort/
diff --git a/chapter25/docs/examples/Capitalize.smp b/chapter25/docs/examples/Capitalize.smp
index 72b5df70..8e31c18f 100644
--- a/chapter25/docs/examples/Capitalize.smp
+++ b/chapter25/docs/examples/Capitalize.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // An implementation of
 // https://sampleprograms.io/projects/capitalize/
diff --git a/chapter25/docs/examples/Dijkstra.smp b/chapter25/docs/examples/Dijkstra.smp
index 57e1fad4..d2f1dc4f 100644
--- a/chapter25/docs/examples/Dijkstra.smp
+++ b/chapter25/docs/examples/Dijkstra.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // An implementation of
 // https://sampleprograms.io/projects/dijkstra/
diff --git a/chapter25/docs/examples/FileIO.smp b/chapter25/docs/examples/FileIO.smp
index 29f037bd..6966755a 100644
--- a/chapter25/docs/examples/FileIO.smp
+++ b/chapter25/docs/examples/FileIO.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // An implementation of
 // https://sampleprograms.io/projects/file-input-output/
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java b/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
index 532f5c70..83616053 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/IterPeeps.java
@@ -62,16 +62,10 @@ public class IterPeeps {
 
     public void addAll( Ary<Node> ary ) { _work.addAll(ary); }
 
-    public void deferInline( CodeGen code, CallEndNode cend ) {
-        if( !code._midAssert )
-            _workInline.push(cend);
-    }
-
     /**
      * Iterate peepholes and inlining to a fixed point
      */
     public void iterate( CodeGen code ) {
-        CallEndNode cend = null;
         boolean didInline = false;
         Ary<Node> defer = new Ary<>(Node.class);
         while( true ) {
@@ -79,18 +73,19 @@ public class IterPeeps {
             iteratePeeps(code);
 
             // Pick an inline candidate, no real heuristic, first come, first served
+            boolean inlined = false;
+            CallEndNode cend;
             while( (cend=_workInline.pop()) != null) {
                 if( cend.isDead() ) continue;
-                if( cend.inline() == -1 ) defer.add(cend);
-                if( cend.inline() > 0 ) break;
-            }
-            // Found an inline candidate, so inline
-            if( cend != null ) {
-                // Inline, run peeps until clean again
-                cend.doInline();
-                didInline = true;
-                continue;
+                byte inline = cend.maybeInline();
+                if( inline == -1 ) defer.add(cend);
+                if( inline > 0 ) {
+                    inlined = true;
+                    break;
+                }
             }
+            // Inlined, run peeps until clean again
+            if( inlined ) { didInline = true; continue; }
             // No more candidates, check the defer list
             if( !didInline ) break; // No more progress, so all the "maybe inline after cleanup" do not progress
             // Some inlining happened, retry all the "try again after cleanup" calls
@@ -102,7 +97,7 @@ public class IterPeeps {
 
     // Run all the code-reduction and type-lifting peeps as possible
     private void iteratePeeps( CodeGen code ) {
-        assert progressOnList(code, _work, true);
+        assert !CodeGen.expensiveAssert(1) || progressOnList(code, _work, true);
         int cnt=0;
 
         Node n;
@@ -110,6 +105,8 @@ public class IterPeeps {
             if( n.isDead() )  continue;
             cnt++;              // Useful for debugging, searching which peephole broke things
             Node x = n.peepholeOpt();
+            if( n instanceof CallEndNode cend )
+                _workInline.push(cend);
             if( x != null ) {
                 if( x.isDead() ) continue;
                 // peepholeOpt can return brand-new nodes, needing an initial type set
@@ -136,7 +133,8 @@ public class IterPeeps {
                 // If there are distant neighbors, move to worklist
                 n.moveDepsToWorklist();
                 JSViewer.show(); // Show again
-                assert progressOnList(code, _work, true); // Very expensive assert
+                // Very expensive assert.
+                assert !CodeGen.expensiveAssert(cnt) || progressOnList(code, _work, true);
             }
             if( n.isUnused() && !(n instanceof StopNode) )
                 n.kill();       // Just plain dead
@@ -174,6 +172,11 @@ public class IterPeeps {
             assert !checkType || monotonic : "Non-monotonic peep: "+n+"#"+n._nid+" old="+n._type+" new="+nval+" inputs="+inputTypes(n)+" peep="+m;
             if( list.on(n) )
                 return null;
+            if( n instanceof CallEndNode cend ) {
+                if( code._iter._workInline.on(cend) )
+                    return null;
+                assert cend.maybeInline() <= 0 : "Inline fired and not on worklist, CallEndNode#"+cend._nid;
+            }
 
             assert n.nOuts() > 0 : "Unused live node: "+n;
             m = n.peepholeOpt();
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java b/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
index 50f5c33b..bcefe996 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/codegen/CodeGen.java
@@ -45,6 +45,19 @@ public class CodeGen {
     /** True when tests deliberately randomize Iter worklist order. */
     public static boolean iterSeedOverridden() { return System.getProperty("simple.iter.seed") != null; }
 
+    // Expensive assert sampling:
+    //   -Dsimple.assert.expensive=0 disables these checks
+    //   -Dsimple.assert.expensive=1 checks every step
+    //   -Dsimple.assert.expensive=N checks once every 1<<N steps
+    private static final int EXPENSIVE_ASSERT_LOG = Integer.getInteger("simple.assert.expensive",8);
+    public static boolean expensiveAssert() { return EXPENSIVE_ASSERT_LOG > 0; }
+    public static boolean expensiveAssert( int trip ) {
+        if( EXPENSIVE_ASSERT_LOG <= 0 ) return false;
+        if( EXPENSIVE_ASSERT_LOG == 1 ) return true;
+        int shift = Math.min(EXPENSIVE_ASSERT_LOG,30);
+        return (trip & ((1<<shift)-1)) == 0;
+    }
+
     // ---------------------------
     // Module Source Root
     public final String _modDir;
@@ -458,7 +471,8 @@ public class CodeGen {
             return null;
         });
         _iter.iterate(this);
-        assert Opto.fixedPointCheck(this);
+        // Expensive assert.
+        assert !expensiveAssert() || Opto.fixedPointCheck(this);
 
         _times[Phase.Iter.ordinal()] = System.currentTimeMillis() - t0;
         return this;
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/codegen/Opto.java b/chapter25/src/main/java/com/seaofnodes/simple/codegen/Opto.java
index 5d4c151d..e8062c90 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/codegen/Opto.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/codegen/Opto.java
@@ -246,8 +246,8 @@ abstract public class Opto {
             // Since n._type changed, visit all output neighbors
             code._iter.addAll(n._outputs);
             n.moveDepsToWorklist(code._iter);
-            // Quadratic (expensive) small-step assert
-            assert worklistCheck(code);
+            // Quadratic (expensive) small-step assert.
+            assert !CodeGen.expensiveAssert(count) || worklistCheck(code);
         }
     }
 
diff --git a/chapter25/src/main/java/com/seaofnodes/simple/node/CallEndNode.java b/chapter25/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
index 061232c7..c9029049 100644
--- a/chapter25/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
+++ b/chapter25/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
@@ -133,19 +133,18 @@ public class CallEndNode extends CFGNode implements MultiNode {
 
     @Override
     public Node idealize() {
+        return null;
+    }
 
-        _inline = inlineCandidate();
-        if( _inline == 1 ) {
-            ReturnNode ret = (ReturnNode)in(1);
-            FunNode fun = ret.fun();
-            doTrivialInlining(fun);
-            return this;
-        }
-        // Delay for cleanup, before cloning
-        if( _inline >= 2 )
-            CodeGen.CODE._iter.deferInline(CodeGen.CODE,this);
+    public byte maybeInline() {
+        byte inline = inlineCandidate();
+        if( CodeGen.CODE._midAssert )
+            return inline;
+        _inline = inline;
+        if( _inline > 0 )
+            doInline();
 
-        return null;
+        return _inline;
     }
 
     // Check if candidate right now, sets no flags
diff --git a/chapter25/src/main/smp/sys.smp b/chapter25/src/main/smp/sys.smp
index 8aef5b68..7705a187 100644
--- a/chapter25/src/main/smp/sys.smp
+++ b/chapter25/src/main/smp/sys.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // top-level default standard library import
 
diff --git a/chapter25/src/main/smp/sys/adt.smp b/chapter25/src/main/smp/sys/adt.smp
index efdad395..a4fe40bf 100644
--- a/chapter25/src/main/smp/sys/adt.smp
+++ b/chapter25/src/main/smp/sys/adt.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Abstract data types.
 val bitset = bitset;
diff --git a/chapter25/src/main/smp/sys/adt/bitset.smp b/chapter25/src/main/smp/sys/adt/bitset.smp
index f56f1cce..d02cd2fe 100644
--- a/chapter25/src/main/smp/sys/adt/bitset.smp
+++ b/chapter25/src/main/smp/sys/adt/bitset.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // A set of non-negative integers, represented one bit per value.
 struct bitset {
diff --git a/chapter25/src/main/smp/sys/ary.smp b/chapter25/src/main/smp/sys/ary.smp
index feade0f5..8312e94c 100644
--- a/chapter25/src/main/smp/sys/ary.smp
+++ b/chapter25/src/main/smp/sys/ary.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Array utilities
 
diff --git a/chapter25/src/main/smp/sys/aryi64.smp b/chapter25/src/main/smp/sys/aryi64.smp
index e4c39ac3..22ee082e 100644
--- a/chapter25/src/main/smp/sys/aryi64.smp
+++ b/chapter25/src/main/smp/sys/aryi64.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Ary/Vector of i64s
 struct aryi64 {
diff --git a/chapter25/src/main/smp/sys/aryu8.smp b/chapter25/src/main/smp/sys/aryu8.smp
index 186a45a3..21cf920b 100644
--- a/chapter25/src/main/smp/sys/aryu8.smp
+++ b/chapter25/src/main/smp/sys/aryu8.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Ary/Vector of u8s - a resizable array of bytes.
 struct aryu8 {
diff --git a/chapter25/src/main/smp/sys/char.smp b/chapter25/src/main/smp/sys/char.smp
index de37968e..22ca4213 100644
--- a/chapter25/src/main/smp/sys/char.smp
+++ b/chapter25/src/main/smp/sys/char.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 val toupper = { u8 c ->
     return c >= 'a' && c <= 'z' ? c - ('a' - 'A') : c;
diff --git a/chapter25/src/main/smp/sys/io.smp b/chapter25/src/main/smp/sys/io.smp
index 3d6be512..33fbdb5e 100644
--- a/chapter25/src/main/smp/sys/io.smp
+++ b/chapter25/src/main/smp/sys/io.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Simple I/O Library
 
diff --git a/chapter25/src/main/smp/sys/libc.smp b/chapter25/src/main/smp/sys/libc.smp
index 6d750f7b..133b5bf7 100644
--- a/chapter25/src/main/smp/sys/libc.smp
+++ b/chapter25/src/main/smp/sys/libc.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // libc bindings:
 //   https://www.man7.org/linux/man-pages/man2/<libc call>.2.html
diff --git a/chapter25/src/main/smp/sys/scan.smp b/chapter25/src/main/smp/sys/scan.smp
index ba91003e..44bedaaa 100644
--- a/chapter25/src/main/smp/sys/scan.smp
+++ b/chapter25/src/main/smp/sys/scan.smp
@@ -1,4 +1,3 @@
-// -*- mode: java;  -*-
 
 // Scanner; a simple string parser.
 struct scan {