From b59f51486393b2fae7b0015bc5099c5514c7335a Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Fri, 13 Jun 2025 15:42:08 -0700
Subject: Chapter 24b: SCCP Across Functions
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Co-authored-by: Tamás Hadházy <85063808+Hels15@users.noreply.github.com>
Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Co-authored-by: Symious <14933944+symious@users.noreply.github.com>
Co-authored-by: Jun Kawasaki <jun784@gmail.com>
Co-authored-by: Hadházy Tamás <helsgithub15@gmail.com>
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
---
 src/test/java/com/seaofnodes/simple/Chapter18Test.java | 10 ++++++----
 src/test/java/com/seaofnodes/simple/Chapter24Test.java | 14 ++++++++++++++
 src/test/java/com/seaofnodes/simple/SccpTest.java      | 18 +++++-------------
 3 files changed, 25 insertions(+), 17 deletions(-)

(limited to 'src/test')

diff --git a/src/test/java/com/seaofnodes/simple/Chapter18Test.java b/src/test/java/com/seaofnodes/simple/Chapter18Test.java
index e5dd259b..b6a0ab57 100644
--- a/src/test/java/com/seaofnodes/simple/Chapter18Test.java
+++ b/src/test/java/com/seaofnodes/simple/Chapter18Test.java
@@ -406,8 +406,7 @@ return g();
     }
 
 
-    // Local SCCP cannot infer this recursive return type. The next chapter
-    // solves across calls and checks the same program's execution results.
+    // Mutual recursion: check results, independent of how much gets inlined.
     @Test
     public void testFcnMutRec() {
         CodeGen code = new CodeGen(
@@ -416,8 +415,11 @@ val is_even = { int x -> x ? is_odd (x-1) : true ; };
 val is_odd  = { int x -> x ? is_even(x-1) : false; };
 return is_even(arg);
 """);
-        try { code.driver(CodeGen.Phase.TypeCheck); fail(); }
-        catch( Parser.ParseException e ) { assertEquals("No defined return type",e.getMessage()); }
+        code.driver(CodeGen.Phase.FinalizeIR);
+        assertEquals("1", Eval2.eval(code, 0));
+        assertEquals("0", Eval2.eval(code, 1));
+        assertEquals("1", Eval2.eval(code, 2));
+        assertEquals("0", Eval2.eval(code, 3));
     }
 
     // Forward ref to 'x' means that
diff --git a/src/test/java/com/seaofnodes/simple/Chapter24Test.java b/src/test/java/com/seaofnodes/simple/Chapter24Test.java
index 4eb1324d..6e0fd95f 100644
--- a/src/test/java/com/seaofnodes/simple/Chapter24Test.java
+++ b/src/test/java/com/seaofnodes/simple/Chapter24Test.java
@@ -17,6 +17,20 @@ import org.junit.Test;
 import static org.junit.Assert.*;
 
 public class Chapter24Test {
+    @Test public void testRecursiveWidening() {
+        String[] srcs = {
+            // Parm(x) must widen even though the recursive result is constant.
+            "val f = { int x, int limit -> x >= limit ? 0 : f(x+1,limit); }; return f(0,arg);",
+            // The growing result has its own cycle, which never crosses Parm(x).
+            "val f = { int x -> x <= 0 ? 0 : f(x-1)+1; }; return f(3);"
+        };
+        for( int i=0; i<srcs.length; i++ )
+            for( long seed : new long[]{0,42,126} ) {
+                var code = new CodeGen(srcs[i],TypeInteger.BOT,seed,true).driver(CodeGen.Phase.LocalSched);
+                assertEquals(i==0 ? "0" : "3",Eval2.eval(code,3));
+            }
+    }
+
     @Test public void testColdLoopSelfConflict() { com.seaofnodes.simple.codegen.RegAllocTestSupport.coldLoopSelfConflict(); }
 
     @Test public void testPrintingDeadFunction() throws Exception {
diff --git a/src/test/java/com/seaofnodes/simple/SccpTest.java b/src/test/java/com/seaofnodes/simple/SccpTest.java
index afa0ec58..cad1b7de 100644
--- a/src/test/java/com/seaofnodes/simple/SccpTest.java
+++ b/src/test/java/com/seaofnodes/simple/SccpTest.java
@@ -7,25 +7,17 @@ import org.junit.Test;
 import static org.junit.Assert.*;
 
 public class SccpTest {
-    @Test public void testLoopFixedPoint() {
-        var code = new CodeGen("int x=1; while(arg) { x=2-x; arg--; } return x;").parse().iter();
-        assertFalse(code.link(code._main).ret().expr()._type.isConstant());
-        code.opto();
-        assertSame(TypeInteger.TRUE,code.link(code._main).ret().expr()._type);
-        code.driver(CodeGen.Phase.LocalSched);
-        assertEquals("1",Eval2.eval(code,4));
-    }
-
-    @Test public void testConservativeCalls() {
+    @Test public void testCallArgumentFlow() {
         var code = new CodeGen("val f={ int x -> x+1; }; return f(1)+f(2);").parse().iter().opto();
         int[] parms = {0};
         code._start.walk(n -> {
             if( n instanceof ParmNode p && "x".equals(p._label) ) {
                 parms[0]++;
-                assertSame(TypeInteger.BOT,p._type);
-                assertTrue(p.fun().in(1) instanceof StartNode);
+                TypeInteger t = (TypeInteger)p._type;
+                assertEquals(1,t._min);
+                assertEquals(2,t._max);
+                assertFalse(p.fun().in(1) instanceof StartNode);
             }
-            if( n instanceof CallEndNode cend ) assertEquals(1,cend.nIns());
             return null;
         });
         assertEquals(1,parms[0]);
-- 
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