From 63a91341fc9087a59c5dafb4ec0e5e6a83c367ca Mon Sep 17 00:00:00 2001
From: Devin Papineau <devin@ajdmp.ca>
Date: Fri, 1 Dec 2023 21:13:35 -0500
Subject: [PATCH] Correct branch folding for HCR guard versioning

This logic has been inadvertently folding the versioning test instead of
the original guard since ce45970e6f92be1148c88c8bfd1b4afb8ae09cb1, which
is effectively the same as not versioning the guards. This can be
expected to have resulted in slower code than intended. Worse, if there
are HCR guards in the loop, then once the fixed-point analysis has
determined that it is possible to version them, they must be versioned
for correctness. This is because other transformations may rely on the
cold side being eliminated from the hot loop. In particular, by failing
to version HCR guards, we could privatize mutable fields even though
they could be modified by a cold call while the loop is still running.
---
 compiler/optimizer/LoopVersioner.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/optimizer/LoopVersioner.cpp b/compiler/optimizer/LoopVersioner.cpp
index c59007d228e..eb3b5f91efb 100644
--- a/compiler/optimizer/LoopVersioner.cpp
+++ b/compiler/optimizer/LoopVersioner.cpp
@@ -4585,7 +4585,7 @@ void TR_LoopVersioner::versionNaturalLoop(TR_RegionStructure *whileLoop, List<TR
          comparisonTrees.add(guard);
 
          bool reverseBranch = false, origLoop = true;
-         FoldConditional fold(this, NULL, guard, reverseBranch, origLoop);
+         FoldConditional fold(this, NULL, tt->getNode(), reverseBranch, origLoop);
          fold.improveLoop();
          }
       }