JIT: Avoid unnecessary write backs during physical promotion

src/coreclr/jit/bitsetasshortlong.h

@@ -45,6 +45,7 @@ class BitSetOps</*BitSetType*/ BitSetShortLongRep,
     static bool               TryAddElemDLong(Env env, BitSetShortLongRep& bs, unsigned i);
     static void               RemoveElemDLong(Env env, BitSetShortLongRep& bs, unsigned i);
     static void               ClearDLong(Env env, BitSetShortLongRep& bs);
+    static void               FillDLong(Env env, BitSetShortLongRep& bs);
     static BitSetShortLongRep MakeUninitArrayBits(Env env);
     static BitSetShortLongRep MakeEmptyArrayBits(Env env);
     static BitSetShortLongRep MakeFullArrayBits(Env env);
@@ -136,6 +137,19 @@ class BitSetOps</*BitSetType*/ BitSetShortLongRep,
         }
     }
 
+    static void FillD(Env env, BitSetShortLongRep& bs)
+    {
+        if (IsShort(env))
+        {
+            bs = (BitSetShortLongRep)size_t(-1);
+        }
+        else
+        {
+            assert(bs != UninitVal());
+            FillDLong(env, bs);
+        }
+    }
+
     static BitSetShortLongRep MakeSingleton(Env env, unsigned bitNum)
     {
         assert(bitNum < BitSetTraits::GetSize(env));
@@ -865,6 +879,20 @@ void BitSetOps</*BitSetType*/ BitSetShortLongRep,
     }
 }
 
+template <typename Env, typename BitSetTraits>
+void BitSetOps</*BitSetType*/ BitSetShortLongRep,
+               /*Brand*/ BSShortLong,
+               /*Env*/ Env,
+               /*BitSetTraits*/ BitSetTraits>::FillDLong(Env env, BitSetShortLongRep& bs)
+{
+    assert(!IsShort(env));
+    unsigned len = BitSetTraits::GetArrSize(env);
+    for (unsigned i = 0; i < len; i++)
+    {
+        bs[i] = size_t(-1);
+    }
+}
+
 template <typename Env, typename BitSetTraits>
 BitSetShortLongRep BitSetOps</*BitSetType*/ BitSetShortLongRep,
                              /*Brand*/ BSShortLong,

src/coreclr/jit/compiler.h

@@ -2514,6 +2514,29 @@ struct LoopSideEffects
     void AddModifiedElemType(Compiler* comp, CORINFO_CLASS_HANDLE structHnd);
 };
 
+// Data structure that keeps track of local definitions inside loops.
+class LoopDefinitions
+{
+    typedef JitHashTable<unsigned, JitSmallPrimitiveKeyFuncs<unsigned>, bool> LocalDefinitionsMap;
+
+    FlowGraphNaturalLoops* m_loops;
+    // For every loop, we track all definitions exclusive to that loop.
+    // Definitions in descendant loops are not kept in their ancestor's maps.
+    LocalDefinitionsMap** m_maps;
+    // Blocks whose IR we have visited to find local definitions in.
+    BitVec m_visitedBlocks;
+
+    LocalDefinitionsMap* GetOrCreateMap(FlowGraphNaturalLoop* loop);
+
+    template <typename TFunc>
+    bool VisitLoopNestMaps(FlowGraphNaturalLoop* loop, TFunc& func);
+public:
+    LoopDefinitions(FlowGraphNaturalLoops* loops);
+
+    template <typename TFunc>
+    void VisitDefinedLocalNums(FlowGraphNaturalLoop* loop, TFunc func);
+};
+
 //  The following holds information about instr offsets in terms of generated code.
 
 enum class IPmappingDscKind

src/coreclr/jit/compiler.hpp

@@ -5205,6 +5205,58 @@ BasicBlockVisit FlowGraphNaturalLoop::VisitRegularExitBlocks(TFunc func)
     return BasicBlockVisit::Continue;
 }
 
+//------------------------------------------------------------------------------
+// LoopDefinitions:VisitLoopNestMaps:
+//   Visit all occurrence maps of the specified loop nest.
+//
+// Type parameters:
+//   TFunc - bool(LocalToOccurrenceMap*) functor that returns true to continue
+//           the visit and false to abort.
+//
+// Parameters:
+//   loop - Root loop of the nest.
+//   func - Functor instance
+//
+// Returns:
+//   True if the visit completed; false if "func" returned false for any map.
+//
+template <typename TFunc>
+bool LoopDefinitions::VisitLoopNestMaps(FlowGraphNaturalLoop* loop, TFunc& func)
+{
+    for (FlowGraphNaturalLoop* child = loop->GetChild(); child != nullptr; child = child->GetSibling())
+    {
+        if (!VisitLoopNestMaps(child, func))
+        {
+            return false;
+        }
+    }
+
+    return func(GetOrCreateMap(loop));
+}
+
+//------------------------------------------------------------------------------
+// LoopDefinitions:VisitDefinedLocalNums:
+//   Call a callback for all locals that are defined in the specified loop.
+//
+// Parameters:
+//   loop - The loop
+//   func - The callback
+//
+template <typename TFunc>
+void LoopDefinitions::VisitDefinedLocalNums(FlowGraphNaturalLoop* loop, TFunc func)
+{
+    auto visit = [=, &func](LocalDefinitionsMap* map) {
+        for (unsigned lclNum : LocalDefinitionsMap::KeyIteration(map))
+        {
+            func(lclNum);
+        }
+
+        return true;
+    };
+
+    VisitLoopNestMaps(loop, visit);
+}
+
 /*****************************************************************************/
 #endif //_COMPILER_HPP_
 /*****************************************************************************/

src/coreclr/jit/lclmorph.cpp

@@ -175,29 +175,6 @@ void Compiler::fgSequenceLocals(Statement* stmt)
     seq.Sequence(stmt);
 }
 
-// Data structure that keeps track of local definitions inside loops.
-class LoopDefinitions
-{
-    typedef JitHashTable<unsigned, JitSmallPrimitiveKeyFuncs<unsigned>, bool> LocalDefinitionsMap;
-
-    FlowGraphNaturalLoops* m_loops;
-    // For every loop, we track all definitions exclusive to that loop.
-    // Definitions in descendant loops are not kept in their ancestor's maps.
-    LocalDefinitionsMap** m_maps;
-    // Blocks whose IR we have visited to find local definitions in.
-    BitVec m_visitedBlocks;
-
-    LocalDefinitionsMap* GetOrCreateMap(FlowGraphNaturalLoop* loop);
-
-    template <typename TFunc>
-    bool VisitLoopNestMaps(FlowGraphNaturalLoop* loop, TFunc& func);
-public:
-    LoopDefinitions(FlowGraphNaturalLoops* loops);
-
-    template <typename TFunc>
-    void VisitDefinedLocalNums(FlowGraphNaturalLoop* loop, TFunc func);
-};
-
 LoopDefinitions::LoopDefinitions(FlowGraphNaturalLoops* loops)
     : m_loops(loops)
 {
@@ -263,7 +240,7 @@ LoopDefinitions::LocalDefinitionsMap* LoopDefinitions::GetOrCreateMap(FlowGraphN
         fgWalkResult PreOrderVisit(GenTree** use, GenTree* user)
         {
             GenTreeLclVarCommon* lcl = (*use)->AsLclVarCommon();
-            if (!lcl->OperIsLocalStore())
+            if (!lcl->OperIsLocalStore() && !lcl->OperIs(GT_LCL_ADDR))
             {
                 return Compiler::WALK_CONTINUE;
             }
@@ -320,58 +297,6 @@ LoopDefinitions::LocalDefinitionsMap* LoopDefinitions::GetOrCreateMap(FlowGraphN
     return map;
 }
 
-//------------------------------------------------------------------------------
-// LoopDefinitions:VisitLoopNestMaps:
-//   Visit all occurrence maps of the specified loop nest.
-//
-// Type parameters:
-//   TFunc - bool(LocalToOccurrenceMap*) functor that returns true to continue
-//           the visit and false to abort.
-//
-// Parameters:
-//   loop - Root loop of the nest.
-//   func - Functor instance
-//
-// Returns:
-//   True if the visit completed; false if "func" returned false for any map.
-//
-template <typename TFunc>
-bool LoopDefinitions::VisitLoopNestMaps(FlowGraphNaturalLoop* loop, TFunc& func)
-{
-    for (FlowGraphNaturalLoop* child = loop->GetChild(); child != nullptr; child = child->GetSibling())
-    {
-        if (!VisitLoopNestMaps(child, func))
-        {
-            return false;
-        }
-    }
-
-    return func(GetOrCreateMap(loop));
-}
-
-//------------------------------------------------------------------------------
-// LoopDefinitions:VisitDefinedLocalNums:
-//   Call a callback for all locals that are defined in the specified loop.
-//
-// Parameters:
-//   loop - The loop
-//   func - The callback
-//
-template <typename TFunc>
-void LoopDefinitions::VisitDefinedLocalNums(FlowGraphNaturalLoop* loop, TFunc func)
-{
-    auto visit = [=, &func](LocalDefinitionsMap* map) {
-        for (unsigned lclNum : LocalDefinitionsMap::KeyIteration(map))
-        {
-            func(lclNum);
-        }
-
-        return true;
-    };
-
-    VisitLoopNestMaps(loop, visit);
-}
-
 struct LocalEqualsLocalAddrAssertion
 {
     // Local num on the LHS