Use unsigned cast for Span_get_Item

Author: pentp

src/coreclr/jit/importer.cpp

@@ -4150,7 +4150,7 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
                 GenTree* ptrToSpan      = impPopStack().val;
                 GenTree* indexClone     = nullptr;
                 GenTree* ptrToSpanClone = nullptr;
-                assert(varTypeIsIntegral(index));
+                assert(genActualType(index) == TYP_INT);
                 assert(ptrToSpan->TypeGet() == TYP_BYREF);
 
 #if defined(DEBUG)
@@ -4177,12 +4177,25 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
                     GenTreeBoundsChk(GT_ARR_BOUNDS_CHECK, TYP_VOID, index, length, SCK_RNGCHK_FAIL);
 
                 // Element access
-                index = impImplicitIorI4Cast(indexClone, TYP_I_IMPL);
+                index = indexClone;
+
+#ifdef TARGET_64BIT
+                if (index->OperGet() == GT_CNS_INT)
+                {
+                    index->gtType = TYP_I_IMPL;
+                }
+                else
+                {
+                    index = gtNewCastNode(TYP_I_IMPL, index, true, TYP_I_IMPL);
+                }
+#endif
+
                 if (elemSize != 1)
                 {
                     GenTree* sizeofNode = gtNewIconNode(elemSize);
                     index               = gtNewOperNode(GT_MUL, TYP_I_IMPL, index, sizeofNode);
                 }
+
                 CORINFO_FIELD_HANDLE ptrHnd    = info.compCompHnd->getFieldInClass(clsHnd, 0);
                 const unsigned       ptrOffset = info.compCompHnd->getFieldOffset(ptrHnd);
                 GenTree*             data      = gtNewFieldRef(TYP_BYREF, ptrHnd, ptrToSpanClone, ptrOffset);