From 840162c586180455e36324f5f041e27956ac0aac Mon Sep 17 00:00:00 2001
From: Cliff Click <cliffc@acm.org>
Date: Sat, 9 Aug 2025 09:13:01 -0700
Subject: do not collapse trivial regions

---
 chapter23/src/main/java/com/seaofnodes/simple/node/RegionNode.java | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'chapter23/src/main/java/com')

diff --git a/chapter23/src/main/java/com/seaofnodes/simple/node/RegionNode.java b/chapter23/src/main/java/com/seaofnodes/simple/node/RegionNode.java
index e25c2380..2b467a8c 100644
--- a/chapter23/src/main/java/com/seaofnodes/simple/node/RegionNode.java
+++ b/chapter23/src/main/java/com/seaofnodes/simple/node/RegionNode.java
@@ -57,8 +57,8 @@ public class RegionNode extends CFGNode {
             return delDef(2);
         }
 
-        // Flatten stack regions (no loops involved)
-        if( getClass() == RegionNode.class ) {
+        // Flatten stacked regions (no loops involved)
+        if( getClass() == RegionNode.class && nIns()>2 ) {
             for( int i=1; i<nIns(); i++ )
                 if( cfg(i) instanceof RegionNode region && region.getClass() == RegionNode.class && region.nIns()>2 && !hasMidUser(region) ) {
                     assert !region.inProgress();
-- 
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