Delete `GTF_VAR_CAST` (#74461)

It is unused.

Tighten an assert in the ref counter.

src/coreclr/jit/compiler.cpp

@@ -9218,10 +9218,6 @@ void cTreeFlags(Compiler* comp, GenTree* tree)
                 {
                     chars += printf("[VAR_USEASG]");
                 }
-                if (tree->gtFlags & GTF_VAR_CAST)
-                {
-                    chars += printf("[VAR_CAST]");
-                }
                 if (tree->gtFlags & GTF_VAR_ITERATOR)
                 {
                     chars += printf("[VAR_ITERATOR]");

src/coreclr/jit/gentree.cpp

@@ -10442,12 +10442,6 @@ void Compiler::gtDispNode(GenTree* tree, IndentStack* indentStack, _In_ _In_opt_
                     --msgLength;
                     break;
                 }
-                if (tree->gtFlags & GTF_VAR_CAST)
-                {
-                    printf("C");
-                    --msgLength;
-                    break;
-                }
                 if (tree->gtFlags & GTF_VAR_CONTEXT)
                 {
                     printf("!");

src/coreclr/jit/gentree.h

@@ -468,11 +468,10 @@ enum GenTreeFlags : unsigned int
 
     GTF_LIVENESS_MASK   = GTF_VAR_DEF | GTF_VAR_USEASG | GTF_VAR_DEATH_MASK,
 
-    GTF_VAR_CAST        = 0x01000000, // GT_LCL_VAR -- has been explicitly cast (variable node may not be type of local)
-    GTF_VAR_ITERATOR    = 0x00800000, // GT_LCL_VAR -- this is a iterator reference in the loop condition
-    GTF_VAR_CLONED      = 0x00400000, // GT_LCL_VAR -- this node has been cloned or is a clone
-    GTF_VAR_CONTEXT     = 0x00200000, // GT_LCL_VAR -- this node is part of a runtime lookup
-    GTF_VAR_FOLDED_IND  = 0x00100000, // GT_LCL_VAR -- this node was folded from *(typ*)&lclVar expression tree in fgMorphSmpOp()
+    GTF_VAR_ITERATOR    = 0x01000000, // GT_LCL_VAR -- this is a iterator reference in the loop condition
+    GTF_VAR_CLONED      = 0x00800000, // GT_LCL_VAR -- this node has been cloned or is a clone
+    GTF_VAR_CONTEXT     = 0x00400000, // GT_LCL_VAR -- this node is part of a runtime lookup
+    GTF_VAR_FOLDED_IND  = 0x00200000, // GT_LCL_VAR -- this node was folded from *(typ*)&lclVar expression tree in fgMorphSmpOp()
                                       // where 'typ' is a small type and 'lclVar' corresponds to a normalized-on-store local variable.
                                       // This flag identifies such nodes in order to make sure that fgDoNormalizeOnStore() is called
                                       // on their parents in post-order morph.
@@ -2313,20 +2312,18 @@ public:
     bool IsReuseRegVal() const
     {
         // This can be extended to non-constant nodes, but not to local or indir nodes.
-        if (IsInvariant() && ((gtFlags & GTF_REUSE_REG_VAL) != 0))
-        {
-            return true;
-        }
-        return false;
+        return OperIsConst() && ((gtFlags & GTF_REUSE_REG_VAL) != 0);
     }
+
     void SetReuseRegVal()
     {
-        assert(IsInvariant());
+        assert(OperIsConst());
         gtFlags |= GTF_REUSE_REG_VAL;
     }
+
     void ResetReuseRegVal()
     {
-        assert(IsInvariant());
+        assert(OperIsConst());
         gtFlags &= ~GTF_REUSE_REG_VAL;
     }
 

src/coreclr/jit/lclvars.cpp

@@ -4452,7 +4452,7 @@ void Compiler::lvaMarkLclRefs(GenTree* tree, BasicBlock* block, Statement* stmt,
 
 #if FEATURE_PARTIAL_SIMD_CALLEE_SAVE
                     // TODO-CQ: If the varType needs partial callee save, conservatively do not enregister
-                    // such variable. In future, need to enable enregisteration for such variables.
+                    // such variable. In future, we should enable enregisteration for such variables.
                     if (!varTypeNeedsPartialCalleeSave(varDsc->GetRegisterType()))
 #endif
                     {
@@ -4463,48 +4463,11 @@ void Compiler::lvaMarkLclRefs(GenTree* tree, BasicBlock* block, Statement* stmt,
             }
         }
 
-        bool allowStructs = false;
-#ifdef UNIX_AMD64_ABI
-        // On System V the type of the var could be a struct type.
-        allowStructs = varTypeIsStruct(varDsc);
-#endif // UNIX_AMD64_ABI
-
-        /* Variables must be used as the same type throughout the method */
-        noway_assert(varDsc->lvType == TYP_UNDEF || tree->gtType == TYP_UNKNOWN || allowStructs ||
-                     genActualType(varDsc->TypeGet()) == genActualType(tree->gtType) ||
-                     (tree->gtType == TYP_BYREF && varDsc->TypeGet() == TYP_I_IMPL) ||
-                     (tree->gtType == TYP_I_IMPL && varDsc->TypeGet() == TYP_BYREF) || (tree->gtFlags & GTF_VAR_CAST) ||
-                     (varTypeIsFloating(varDsc) && varTypeIsFloating(tree)) ||
-                     (varTypeIsStruct(varDsc) == varTypeIsStruct(tree)));
-
-        /* Remember the type of the reference */
-
-        if (tree->gtType == TYP_UNKNOWN || varDsc->lvType == TYP_UNDEF)
-        {
-            varDsc->lvType = tree->gtType;
-            noway_assert(genActualType(varDsc->TypeGet()) == tree->gtType); // no truncation
-        }
-
-#ifdef DEBUG
-        if (tree->gtFlags & GTF_VAR_CAST)
-        {
-            // it should never be bigger than the variable slot
-
-            // Trees don't store the full information about structs
-            // so we can't check them.
-            if (tree->TypeGet() != TYP_STRUCT)
-            {
-                unsigned treeSize = genTypeSize(tree->TypeGet());
-                unsigned varSize  = genTypeSize(varDsc->TypeGet());
-                if (varDsc->TypeGet() == TYP_STRUCT)
-                {
-                    varSize = varDsc->lvSize();
-                }
-
-                assert(treeSize <= varSize);
-            }
-        }
-#endif
+        // Check that the LCL_VAR node has the same type as the underlying variable, save a few mismatches we allow.
+        assert(tree->TypeIs(varDsc->TypeGet(), genActualType(varDsc)) ||
+               (tree->TypeIs(TYP_I_IMPL) && (varDsc->TypeGet() == TYP_BYREF)) || // Created for spill clique import.
+               (tree->TypeIs(TYP_BYREF) && (varDsc->TypeGet() == TYP_I_IMPL)) || // Created by inliner substitution.
+               (tree->TypeIs(TYP_INT) && (varDsc->TypeGet() == TYP_LONG)));      // Created by "optNarrowTree".
     }
 }
 

src/coreclr/jit/morph.cpp

@@ -4548,8 +4548,8 @@ GenTree* Compiler::fgMorphIndexAddr(GenTreeIndexAddr* indexAddr)
         {
             unsigned arrRefTmpNum = lvaGrabTemp(true DEBUGARG("arr expr"));
             arrRefDefn            = gtNewTempAssign(arrRefTmpNum, arrRef);
-            arrRef                = gtNewLclvNode(arrRefTmpNum, arrRef->TypeGet());
-            arrRef2               = gtNewLclvNode(arrRefTmpNum, arrRef->TypeGet());
+            arrRef                = gtNewLclvNode(arrRefTmpNum, lvaGetDesc(arrRefTmpNum)->TypeGet());
+            arrRef2               = gtNewLclvNode(arrRefTmpNum, lvaGetDesc(arrRefTmpNum)->TypeGet());
         }
         else
         {
@@ -4563,8 +4563,8 @@ GenTree* Compiler::fgMorphIndexAddr(GenTreeIndexAddr* indexAddr)
         {
             unsigned indexTmpNum = lvaGrabTemp(true DEBUGARG("index expr"));
             indexDefn            = gtNewTempAssign(indexTmpNum, index);
-            index                = gtNewLclvNode(indexTmpNum, index->TypeGet());
-            index2               = gtNewLclvNode(indexTmpNum, index->TypeGet());
+            index                = gtNewLclvNode(indexTmpNum, lvaGetDesc(indexTmpNum)->TypeGet());
+            index2               = gtNewLclvNode(indexTmpNum, lvaGetDesc(indexTmpNum)->TypeGet());
         }
         else
         {
@@ -17285,7 +17285,7 @@ bool Compiler::fgMorphArrayOpsStmt(MorphMDArrayTempCache* pTempCache, BasicBlock
                     // Side-effect; create a temp.
                     // unsigned newIdxLcl    = m_compiler->lvaGrabTemp(true DEBUGARG("MD array index copy"));
                     unsigned newIdxLcl    = m_pTempCache->GrabTemp(idx->TypeGet());
-                    GenTree* newIdx       = m_compiler->gtNewLclvNode(newIdxLcl, idx->TypeGet());
+                    GenTree* newIdx       = m_compiler->gtNewLclvNode(newIdxLcl, genActualType(idx));
                     idxToUse[i]           = newIdx;
                     idxToCopy[i]          = newIdxLcl;
                     anyIdxWithSideEffects = true;

src/coreclr/jit/morphblock.cpp

@@ -1432,7 +1432,6 @@ GenTree* MorphCopyBlockHelper::CopyFieldByField()
                             (m_srcVarDsc->lvType == TYP_STRUCT) ? m_srcVarDsc->lvExactSize : genTypeSize(m_srcVarDsc);
                         if (destSize == srcSize)
                         {
-                            m_srcLclNode->gtFlags |= GTF_VAR_CAST;
                             m_srcLclNode->ChangeOper(GT_LCL_FLD);
                             m_srcLclNode->gtType = destType;
                             m_comp->lvaSetVarDoNotEnregister(m_srcLclNum DEBUGARG(DoNotEnregisterReason::LocalField));

src/coreclr/jit/optimizer.cpp

@@ -5850,12 +5850,6 @@ bool Compiler::optNarrowTree(GenTree* tree, var_types srct, var_types dstt, Valu
 
                     tree->gtType = dstt;
                     tree->SetVNs(vnpNarrow);
-
-                    /* Make sure we don't mess up the variable type */
-                    if ((oper == GT_LCL_VAR) || (oper == GT_LCL_FLD))
-                    {
-                        tree->gtFlags |= GTF_VAR_CAST;
-                    }
                 }
 
                 return true;

src/coreclr/jit/valuenum.cpp

@@ -8512,7 +8512,8 @@ void Compiler::fgValueNumberTree(GenTree* tree)
                             }
                             else
                             {
-                                assert((varDsc->TypeGet() == TYP_I_IMPL) && lcl->TypeIs(TYP_BYREF));
+                                assert(((varDsc->TypeGet() == TYP_I_IMPL) && lcl->TypeIs(TYP_BYREF)) ||
+                                       ((varDsc->TypeGet() == TYP_BYREF) && lcl->TypeIs(TYP_I_IMPL)));
                                 lcl->gtVNPair = wholeLclVarVNP;
                             }
                         }