From df44968440fe35301e2bf55e77c8c82958a4df9b Mon Sep 17 00:00:00 2001
From: Dhruv Chopra <Dhruv.C.Chopra@ibm.com>
Date: Fri, 10 Nov 2023 23:11:51 -0500
Subject: [PATCH] Make globalReg clobberable in Z iRegStoreEvaluator

If the iRegStoreEvaluator generates an LGFR to sign extend, it is
incorrect to assume that the iRegStore's child is clobberable. We must
preserve the original value when sign extending. This commit fixes
this issue by using the gprClobberEvaluate routine so that the sign
extension is performed in a different register, and we don't potentially
overwrite the upper-half data in the original register.
---
 compiler/z/codegen/OMRTreeEvaluator.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/z/codegen/OMRTreeEvaluator.cpp b/compiler/z/codegen/OMRTreeEvaluator.cpp
index 69de7b771b3..ea9c62b85c2 100644
--- a/compiler/z/codegen/OMRTreeEvaluator.cpp
+++ b/compiler/z/codegen/OMRTreeEvaluator.cpp
@@ -13787,7 +13787,7 @@ OMR::Z::TreeEvaluator::iRegStoreEvaluator(TR::Node * node, TR::CodeGenerator * c
 
    if (!useLGHI)
       {
-      globalReg = cg->evaluate(value);
+      globalReg = needsLGFR && noLGFgenerated ? cg->gprClobberEvaluate(value) : cg->evaluate(value);
       }
    else
       {