From a0bee26d769adf61ed0a292983992a70e4e261c3 Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Mon, 13 Jan 2025 16:36:11 -0800
Subject: Prevent self-inlining

Better error message for self-calling functions
---
 .../com/seaofnodes/simple/node/CallEndNode.java    | 31 +++++++++++++---------
 .../com/seaofnodes/simple/node/ReturnNode.java     |  2 ++
 2 files changed, 21 insertions(+), 12 deletions(-)

(limited to 'chapter18/src/main/java/com')

diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
index a2866d65..07a2b5a3 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/CallEndNode.java
@@ -50,24 +50,31 @@ public class CallEndNode extends CFGNode implements MultiNode {
             CallNode call = call();
             Node fptr = call.fptr();
             if( fptr.nOuts() == 1 && // Only user is this call
-                fptr instanceof ConstantNode &&
+                fptr instanceof ConstantNode && // We have an immediate call
                 // Function is being called, and its not-null
-                fptr._type instanceof TypeFunPtr tfp && tfp.notNull()) {
+                fptr._type instanceof TypeFunPtr tfp && tfp.notNull() &&
+                // Arguments are correct
+                call.err()==null ) {
                 ReturnNode ret = (ReturnNode)in(1);
                 FunNode fun = ret.fun();
                 // Expecting Start, and the Call
                 if( fun.nIns()==3 ) {
                     assert fun.in(1) instanceof StartNode && fun.in(2)==call;
-
-                    // Trivial inline: rewrite
-                    _folding = true;
-                    // Rewrite Fun so the normal RegionNode ideal collapses
-                    fun._folding = true;
-                    fun.setDef(1,Parser.XCTRL); // No default/unknown StartNode caller
-                    fun.setDef(2,call.ctrl());  // Bypass the Call;
-                    fun.ret().setDef(3,null);   // Return is folding also
-                    IterPeeps.addAll(fun._outputs);
-                    return this;
+                    // Disallow self-recursive inlining (loop unrolling by another name)
+                    CFGNode idom = call;
+                    while( !(idom instanceof FunNode fun2) )
+                        idom = idom.idom();
+                    if( idom != fun ) {
+                        // Trivial inline: rewrite
+                        _folding = true;
+                        // Rewrite Fun so the normal RegionNode ideal collapses
+                        fun._folding = true;
+                        fun.setDef(1,Parser.XCTRL); // No default/unknown StartNode caller
+                        fun.setDef(2,call.ctrl());  // Bypass the Call;
+                        fun.ret().setDef(3,null);   // Return is folding also
+                        IterPeeps.addAll(fun._outputs);
+                        return this;
+                    }
                 } else {
                     fun.addDep(this);
                 }
diff --git a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index 2fe722c6..e543f9ea 100644
--- a/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter18/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -117,6 +117,8 @@ public class ReturnNode extends CFGNode {
     }
 
     static Parser.ParseException mixerr( boolean ti, boolean tf, boolean tp, boolean tn, Parser.Lexer loc ) {
+        if( !ti && !tf && !tp && !tn )
+            return Parser.error("No defined return type", loc);
         SB sb = new SB().p("No common type amongst ");
         if( ti ) sb.p("int and ");
         if( tf ) sb.p("f64 and ");
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