Move the "do not zero-extend setcc" to lowering

It is XARCH-specific and moving it eliminates questionable code
that is trying to compensate for CSE changing the store.

src/coreclr/jit/lowerxarch.cpp

@@ -163,6 +163,12 @@ void Lowering::LowerStoreIndir(GenTreeStoreInd* node)
         }
     }
 
+    // Optimization: do not unnecessarily zero-extend the result of setcc.
+    if (varTypeIsByte(node) && (node->Data()->OperIsCompare() || node->Data()->OperIs(GT_SETCC)))
+    {
+        node->Data()->ChangeType(TYP_BYTE);
+    }
+
     ContainCheckStoreIndir(node);
 }
 

src/coreclr/jit/morph.cpp

@@ -13394,23 +13394,8 @@ GenTree* Compiler::fgMorphSmpOp(GenTree* tree, MorphAddrContext* mac)
                         tree->AsOp()->gtOp2 = op2 = op2->AsCast()->CastOp();
                     }
                 }
-                else if (op2->OperIsCompare() && varTypeIsByte(effectiveOp1->TypeGet()))
-                {
-                    /* We don't need to zero extend the setcc instruction */
-                    op2->gtType = TYP_BYTE;
-                }
             }
-            // If we introduced a CSE we may need to undo the optimization above
-            // (i.e. " op2->gtType = TYP_BYTE;" which depends upon op1 being a GT_IND of a byte type)
-            // When we introduce the CSE we remove the GT_IND and subsitute a GT_LCL_VAR in it place.
-            else if (op2->OperIsCompare() && (op2->gtType == TYP_BYTE) && (op1->gtOper == GT_LCL_VAR))
-            {
-                unsigned   varNum = op1->AsLclVarCommon()->GetLclNum();
-                LclVarDsc* varDsc = &lvaTable[varNum];
 
-                /* We again need to zero extend the setcc instruction */
-                op2->gtType = varDsc->TypeGet();
-            }
             fgAssignSetVarDef(tree);
 
             /* We can't CSE the LHS of an assignment */