4 files changed, 30 insertions, 19 deletions

diff --git a/src/jit/compiler.h b/src/jit/compiler.h
index e5d4d67efe..570d8d9c8e 100644
--- a/src/jit/compiler.h
+++ b/src/jit/compiler.h
@@ -307,6 +307,9 @@ public:
     unsigned char lvClassInfoUpdated : 1; // true if this var has updated class handle or exactness
 #endif
 
+    unsigned char lvImplicitlyReferenced : 1; // true if there are non-IR references to this local (prolog, epilog, gc,
+                                              // eh)
+
     union {
         unsigned lvFieldLclStart; // The index of the local var representing the first field in the promoted struct
                                   // local.  For implicit byref parameters, this gets hijacked between
@@ -604,6 +607,11 @@ private:
 public:
     unsigned short lvRefCnt() const
     {
+        if (lvImplicitlyReferenced && (m_lvRefCnt == 0))
+        {
+            return 1;
+        }
+
         return m_lvRefCnt;
     }
 
@@ -627,6 +635,11 @@ public:
 
     unsigned lvRefCntWtd() const
     {
+        if (lvImplicitlyReferenced && (m_lvRefCntWtd == 0))
+        {
+            return BB_UNITY_WEIGHT;
+        }
+
         return m_lvRefCntWtd;
     }
 
diff --git a/src/jit/compiler.hpp b/src/jit/compiler.hpp
index c4a50c0fa9..da00abcd03 100644
--- a/src/jit/compiler.hpp
+++ b/src/jit/compiler.hpp
@@ -1797,9 +1797,8 @@ inline unsigned Compiler::lvaGrabTempWithImplicitUse(bool shortLifetime DEBUGARG
     // address-exposed -- DoNotEnregister should suffice?
     lvaSetVarAddrExposed(lclNum);
 
-    // We need lvRefCnt to be non-zero to prevent various asserts from firing.
-    varDsc->setLvRefCnt(1);
-    varDsc->setLvRefCntWtd(BB_UNITY_WEIGHT);
+    // Note the implicit use
+    varDsc->lvImplicitlyReferenced = 1;
 
     return lclNum;
 }
diff --git a/src/jit/lclvars.cpp b/src/jit/lclvars.cpp
index e72ae11cf5..00110b0e6a 100644
--- a/src/jit/lclvars.cpp
+++ b/src/jit/lclvars.cpp
@@ -4026,10 +4026,8 @@ void Compiler::lvaMarkLocalVars()
 
             lvaTable[info.compLvFrameListRoot].lvType = TYP_I_IMPL;
 
-            /* Set the refCnt, it is used in the prolog and return block(s) */
-
-            lvaTable[info.compLvFrameListRoot].setLvRefCnt(2);
-            lvaTable[info.compLvFrameListRoot].setLvRefCntWtd(2 * BB_UNITY_WEIGHT);
+            // This local has implicit prolog and epilog references
+            lvaTable[info.compLvFrameListRoot].lvImplicitlyReferenced = 1;
         }
     }
 
@@ -4148,16 +4146,16 @@ void Compiler::lvaMarkLocalVars()
     }
 #endif
 
-    if (lvaKeepAliveAndReportThis() && lvaTable[0].lvRefCnt() == 0)
+    if (lvaKeepAliveAndReportThis())
     {
-        lvaTable[0].setLvRefCnt(1);
+        lvaTable[0].lvImplicitlyReferenced = 1;
         // This isn't strictly needed as we will make a copy of the param-type-arg
         // in the prolog. However, this ensures that the LclVarDsc corresponding to
         // info.compTypeCtxtArg is valid.
     }
-    else if (lvaReportParamTypeArg() && lvaTable[info.compTypeCtxtArg].lvRefCnt() == 0)
+    else if (lvaReportParamTypeArg())
     {
-        lvaTable[info.compTypeCtxtArg].setLvRefCnt(1);
+        lvaTable[info.compTypeCtxtArg].lvImplicitlyReferenced = 1;
     }
 
     lvaLocalVarRefCounted = true;
@@ -4176,12 +4174,8 @@ void Compiler::lvaAllocOutgoingArgSpaceVar()
     {
         lvaOutgoingArgSpaceVar = lvaGrabTemp(false DEBUGARG("OutgoingArgSpace"));
 
-        lvaTable[lvaOutgoingArgSpaceVar].lvType = TYP_LCLBLK;
-
-        /* Set the refCnts */
-
-        lvaTable[lvaOutgoingArgSpaceVar].setLvRefCnt(1);
-        lvaTable[lvaOutgoingArgSpaceVar].setLvRefCntWtd(BB_UNITY_WEIGHT);
+        lvaTable[lvaOutgoingArgSpaceVar].lvType                 = TYP_LCLBLK;
+        lvaTable[lvaOutgoingArgSpaceVar].lvImplicitlyReferenced = 1;
     }
 
     noway_assert(lvaOutgoingArgSpaceVar >= info.compLocalsCount && lvaOutgoingArgSpaceVar < lvaCount);
diff --git a/src/jit/liveness.cpp b/src/jit/liveness.cpp
index 3c34681daa..9f8910f1e3 100644
--- a/src/jit/liveness.cpp
+++ b/src/jit/liveness.cpp
@@ -1047,9 +1047,14 @@ void Compiler::fgExtendDbgLifetimes()
     unsigned lclNum = 0;
     for (LclVarDsc *varDsc = lvaTable; lclNum < lvaCount; lclNum++, varDsc++)
     {
-        if (varDsc->lvRefCnt() == 0 && varDsc->lvIsRegArg)
+        if (lclNum >= info.compArgsCount)
         {
-            varDsc->setLvRefCnt(1);
+            break; // early exit for loop
+        }
+
+        if (varDsc->lvIsRegArg)
+        {
+            varDsc->lvImplicitlyReferenced = true;
         }
     }