Initialize fieldClassReg for static unresolved reads

When generating code for a watched field event, if an unresolved static field is being read, we do not intialize the fieldClassReg correctly. The fieldClassReg is used to test if a field is being watched. Failure to initialize this register correctly results in an invalid test being generated at runtime, causing a bug. This commit correctly initializes the fieldClassReg for the missing corner case. Signed-off-by: Dhruv Chopra <[email protected]>
eclipse-openj9 · Jun 27, 2019 · cf5e106 · cf5e106
1 parent 8bf50f5
commit cf5e106
Showing 1 changed file with 6 additions and 2 deletions.
diff --git a/runtime/compiler/x/codegen/J9TreeEvaluator.cpp b/runtime/compiler/x/codegen/J9TreeEvaluator.cpp
@@ -12760,11 +12760,15 @@ J9::X86::TreeEvaluator::generateTestAndReportFieldWatchInstructions(TR::CodeGene
          }
       else
          {
-         fieldClassReg = cg->allocateRegister();
          if (isWrite)
             {
+            fieldClassReg = cg->allocateRegister();
             generateRegMemInstruction(LRegMem(), node, fieldClassReg, generateX86MemoryReference(sideEffectRegister, fej9->getOffsetOfClassFromJavaLangClassField(), cg), cg);
             }
+         else
+            {
+            fieldClassReg = sideEffectRegister;
+            }
          classFlagsMemRef = generateX86MemoryReference(fieldClassReg, fej9->getOffsetOfClassFlags(), cg);
          }
       }
@@ -12787,7 +12791,7 @@ J9::X86::TreeEvaluator::generateTestAndReportFieldWatchInstructions(TR::CodeGene
    deps->stopAddingConditions();
    generateLabelInstruction(LABEL, node, endLabel, deps, cg);
 
-   if (isInstanceField || (!isResolved) || isAOTCompile)
+   if (isInstanceField || (!isResolved && isWrite) || isAOTCompile)
       {
       cg->stopUsingRegister(fieldClassReg);
       }