Chapter 24a: SCCP Within a Functionlinear-chapter24a

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>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java b/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
index b60adce7..0304c6a1 100644
--- a/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
+++ b/src/test/java/com/seaofnodes/simple/codegen/RegAllocTestSupport.java
@@ -249,6 +249,33 @@ public class RegAllocTestSupport {
         assertFalse("A fixed definition clobbers even before coloring",uncolored.sameBlockNoClobber(copy));
     }
 
+    public static void coldLoopSelfConflict() {
+        for( boolean phiConflict : new boolean[]{false,true} ) {
+            CodeGen code = graph();
+            RegAlloc alloc = new RegAlloc(code);
+            Op init = new Op(A,null,null,false,code._start);
+            LoopNode loop = new LoopNode(null,code._start);
+            PhiNode phi = new PhiNode("loop",TypeInteger.BOT,loop,init,null);
+            Op back = new Op(A,A,null,false,loop,phi);
+            phi.setDef(2,back);
+            Op use = new Op(null,A,null,false,loop,phi);
+            loop.setDef(2,loop);
+            LRG lrg = alloc.newLRG(phi);
+            lrg._mask = A;
+            alloc.union(lrg,init); alloc.union(lrg,back);
+            lrg.selfConflict(back);
+            if( phiConflict ) lrg.selfConflict(phi);
+            assertTrue(alloc.splitSelfConflict((byte)0,lrg));
+            assertSame(phi,use.in(1)); // First try leaves the hot definition alone.
+            assertSame(back,phi.in(2));
+            if( phiConflict ) assertTrue(phi.in(1) instanceof SplitNode);
+            // Even if the first attempt made no graph change, retry must split.
+            assertTrue(alloc.splitSelfConflict((byte)1,lrg));
+            assertTrue(phi.in(2) instanceof SplitNode);
+            if( phiConflict ) assertTrue(use.in(1) instanceof SplitNode);
+        }
+    }
+
     public static void copyForward() throws Exception {
         // Forwarding, fixed operand, two-address tie, intervening clobber,
         // another user, and a scheduling-only edge.