Major bugfix around unscheduable graphs

Robust assert about all data ops are schedulable.
Utiltiies for several places domionator-like stuff is used.
Removing a Phi with matching null/not-null values is now more robust; removes a major source if scheduling misalignment.
Big comments about what gets covered by a null check, or not.
Permanent list of fuzzer seeds that used to fail

2 files changed, 26 insertions, 0 deletions

diff --git a/chapter25/src/test/java/com/seaofnodes/simple/Chapter25Test.java b/chapter25/src/test/java/com/seaofnodes/simple/Chapter25Test.java
index f5e3d752..2677de5e 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/Chapter25Test.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/Chapter25Test.java
@@ -83,6 +83,14 @@ public class Chapter25Test {
         assertEquals("return 0;",code.print());
     }
 
+    @Test
+    public void testFuzzerBadLCA() {
+        new CodeGen("""
+            int v0=arg;
+            if(v0&&--v0?0:arg) {}
+            """).driver(CodeGen.Phase.LocalSched);
+    }
+
     @Test @Ignore
     public void testModule0() throws IOException {
         String MODDIR = "src/test/java/com/seaofnodes/simple/test0";
diff --git a/chapter25/src/test/java/com/seaofnodes/simple/fuzzer/Fuzzer.java b/chapter25/src/test/java/com/seaofnodes/simple/fuzzer/Fuzzer.java
index 37fa03a6..223515f8 100644
--- a/chapter25/src/test/java/com/seaofnodes/simple/fuzzer/Fuzzer.java
+++ b/chapter25/src/test/java/com/seaofnodes/simple/fuzzer/Fuzzer.java
@@ -163,6 +163,24 @@ public class Fuzzer {
         check(sb.toString(), valid, seed);
     }
 
+    /**
+     * Run one seed as a regression test.  Unlike the exploratory fuzzer path,
+     * this deliberately does not reduce on failure; old bad seeds should fail
+     * fast with the seed visible in the JUnit assertion.
+     */
+    public void fuzzPeepsRegression(long seed) {
+        var rand = new Random(seed);
+        var sb = new StringBuilder();
+        var valid = new ScriptGenerator(rand, sb, true).genProgram();
+        try {
+            runCheck(sb.toString(), valid);
+        } catch( Throwable e ) {
+            AssertionError ae = new AssertionError("Fuzzer regression seed failed: "+seed);
+            ae.initCause(e);
+            throw ae;
+        }
+    }
+
 
     /**
      * Check that no exceptions happened.