Optimize arrays with stable elements

- array elements are considered stable if their values are constant unless they are zero
eclipse · Nov 26, 2021 · 447964f · 447964f
1 parent f76321a
commit 447964f
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Showing 5 changed files with 25 additions and 5 deletions.
diff --git a/compiler/env/OMRKnownObjectTable.cpp b/compiler/env/OMRKnownObjectTable.cpp
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2020 IBM Corp. and others
+ * Copyright (c) 2000, 2021 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -86,6 +86,14 @@ OMR::KnownObjectTable::isArrayWithConstantElements(Index index)
    return false;
    }
 
+bool
+OMR::KnownObjectTable::isArrayWithStableElements(Index index)
+   {
+   TR_ASSERT(index != UNKNOWN && 0 <= index && index < self()->getEndIndex(), "isArrayWithStableElements(%d): index must be in range 0..%d", index, self()->getEndIndex());
+   return false;
+   }
+
+
 uintptr_t *
 OMR::KnownObjectTable::getPointerLocation(Index index)
    {

diff --git a/compiler/env/OMRKnownObjectTable.hpp b/compiler/env/OMRKnownObjectTable.hpp
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2020 IBM Corp. and others
+ * Copyright (c) 2000, 2021 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -87,6 +87,10 @@ class OMR_EXTENSIBLE KnownObjectTable
    // API for checking if an known object is an array with immutable elements
    bool isArrayWithConstantElements(Index index);
 
+   // API for checking if an known object is an array whose elements are immutable
+   // unless they are zero
+   bool isArrayWithStableElements(Index index);
+
    Index getOrCreateIndexAt(uintptr_t *objectReferenceLocation);
    Index getOrCreateIndexAt(uintptr_t *objectReferenceLocation, bool isArrayWithConstantElements);
    Index getExistingIndexAt(uintptr_t *objectReferenceLocation);

diff --git a/compiler/optimizer/VPConstraint.cpp b/compiler/optimizer/VPConstraint.cpp
@@ -623,6 +623,13 @@ bool TR::VPKnownObject::isArrayWithConstantElements(TR::Compilation * comp)
    return knot->isArrayWithConstantElements(_index);
    }
 
+bool TR::VPKnownObject::isArrayWithStableElements(TR::Compilation * comp)
+   {
+   TR::KnownObjectTable *knot = comp->getKnownObjectTable();
+   TR_ASSERT(knot, "TR::KnownObjectTable should not be null");
+   return knot->isArrayWithStableElements(_index);
+   }
+
 TR_YesNoMaybe TR::VPClassType::isArray()
    {
    if (_sig[0] == '[')

diff --git a/compiler/optimizer/VPConstraint.hpp b/compiler/optimizer/VPConstraint.hpp
@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2020 IBM Corp. and others
+ * Copyright (c) 2000, 2021 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -960,7 +960,8 @@ class VPKnownObject : public TR::VPFixedClass
    virtual TR::VPConstraint *intersect1(TR::VPConstraint *other, OMR::ValuePropagation *vp);
 
    virtual TR_YesNoMaybe isJavaLangClassObject();
-   virtual bool isArrayWithConstantElements(TR::Compilation * comp);
+   bool isArrayWithConstantElements(TR::Compilation * comp);
+   bool isArrayWithStableElements(TR::Compilation * comp);
 
    virtual bool mustBeEqual(TR::VPConstraint *other, OMR::ValuePropagation *vp);
    virtual bool mustBeNotEqual(TR::VPConstraint *other, OMR::ValuePropagation *vp);

diff --git a/compiler/optimizer/VPHandlers.cpp b/compiler/optimizer/VPHandlers.cpp
@@ -410,7 +410,7 @@ static bool tryFoldCompileTimeLoad(
                   // Invalidate alias info so that it can be recomputed in the next optimization that needs it
                   vp->optimizer()->setAliasSetsAreValid(false);
                   }
-               else
+               else if (!constraint->getKnownObject()->isArrayWithStableElements(vp->comp()))
                   break;
                }