Use unsigned casts for array/Span indexers (#57970)

* Improve TP for Span_get_Item

* Use unsigned casts for array length/index

* 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)
@@ -4177,13 +4177,29 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
                     GenTreeBoundsChk(GT_ARR_BOUNDS_CHECK, TYP_VOID, index, length, SCK_RNGCHK_FAIL);
 
                 // Element access
-                GenTree*             indexIntPtr = impImplicitIorI4Cast(indexClone, TYP_I_IMPL);
-                GenTree*             sizeofNode  = gtNewIconNode(elemSize);
-                GenTree*             mulNode     = gtNewOperNode(GT_MUL, TYP_I_IMPL, indexIntPtr, 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);
-                GenTree*             result      = gtNewOperNode(GT_ADD, TYP_BYREF, data, mulNode);
+                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);
+                GenTree*             result    = gtNewOperNode(GT_ADD, TYP_BYREF, data, index);
 
                 // Prepare result
                 var_types resultType = JITtype2varType(sig->retType);

src/coreclr/jit/morph.cpp

@@ -5685,7 +5685,7 @@ GenTree* Compiler::fgMorphArrayIndex(GenTree* tree)
 
         if (bndsChkType != TYP_INT)
         {
-            arrLen = gtNewCastNode(bndsChkType, arrLen, false, bndsChkType);
+            arrLen = gtNewCastNode(bndsChkType, arrLen, true, bndsChkType);
         }
 
         GenTreeBoundsChk* arrBndsChk = new (this, GT_ARR_BOUNDS_CHECK)
@@ -5714,7 +5714,7 @@ GenTree* Compiler::fgMorphArrayIndex(GenTree* tree)
         }
         else
         {
-            index = gtNewCastNode(TYP_I_IMPL, index, false, TYP_I_IMPL);
+            index = gtNewCastNode(TYP_I_IMPL, index, true, TYP_I_IMPL);
         }
     }
 #endif // TARGET_64BIT