Optimize Array.Clear using SpanHelpers (#18101)

Reimplement most of Array.Clear in managed code using Span Clear helpers.

Fixes dotnet/corefx#29848

2 files changed, 11 insertions, 33 deletions

diff --git a/src/classlibnative/bcltype/arraynative.cpp b/src/classlibnative/bcltype/arraynative.cpp
index b813b71638..d05f0ca1fb 100644
--- a/src/classlibnative/bcltype/arraynative.cpp
+++ b/src/classlibnative/bcltype/arraynative.cpp
@@ -1070,48 +1070,25 @@ FCIMPL6(void, ArrayNative::ArrayCopy, ArrayBase* m_pSrc, INT32 m_iSrcIndex, Arra
 FCIMPLEND
 
 
-FCIMPL3(void, ArrayNative::ArrayClear, ArrayBase* pArrayUNSAFE, INT32 iIndex, INT32 iLength)
+FCIMPL5(void*, ArrayNative::GetRawArrayGeometry, ArrayBase* pArray, UINT32* pNumComponents, UINT32* pElementSize, INT32* pLowerBound, CLR_BOOL* pContainsGCPointers)
 {
-    FCALL_CONTRACT;
-
-    BASEARRAYREF pArray = (BASEARRAYREF)pArrayUNSAFE;
-
-    HELPER_METHOD_FRAME_BEGIN_1(pArray);
-
-    // cannot pass null for array
-    if (pArray == NULL)
-        COMPlusThrowArgumentNull(W("array"), W("ArgumentNull_Array"));
-
-    // array must be an array
-    _ASSERTE(pArray->GetMethodTable()->IsArray());
-
-    // array bounds checking
-    int lb = pArray->GetLowerBoundsPtr()[0];
-    if (iIndex < lb || (iIndex - lb) < 0 || iLength < 0)
-        COMPlusThrow(kIndexOutOfRangeException);
+   VALIDATEOBJECT(pArray);
 
-    if ((iIndex - lb) > (int)pArray->GetNumComponents() - iLength)
-        COMPlusThrow(kIndexOutOfRangeException);
+   _ASSERTE(pArray != NULL);
 
-    if (iLength > 0)
-    {
-        char* array = (char*)pArray->GetDataPtr();
-
-        SIZE_T size = pArray->GetComponentSize();
-        _ASSERTE(size >= 1);
+    MethodTable *pMT = pArray->GetMethodTable();
 
-        ZeroMemoryInGCHeap(array + (iIndex - lb) * size, iLength * size);
-    }
+    *pNumComponents = pArray->GetNumComponents();
+    *pElementSize = pMT->RawGetComponentSize();
+    *pLowerBound = pArray->GetLowerBoundsPtr()[0];
+    *pContainsGCPointers = !!pMT->ContainsPointers();
 
-    HELPER_METHOD_FRAME_END();
+    return (BYTE*)pArray + ArrayBase::GetDataPtrOffset(pMT);
 }
 FCIMPLEND
 
 
 
-
-
-
 // Check we're allowed to create an array with the given element type.
 void ArrayNative::CheckElementType(TypeHandle elementType)
 {
diff --git a/src/classlibnative/bcltype/arraynative.h b/src/classlibnative/bcltype/arraynative.h
index c742bc21a7..3b6d5495f3 100644
--- a/src/classlibnative/bcltype/arraynative.h
+++ b/src/classlibnative/bcltype/arraynative.h
@@ -35,7 +35,8 @@ public:
     static FCDECL1(void, Initialize, ArrayBase* pArray);
 
     static FCDECL6(void, ArrayCopy, ArrayBase* m_pSrc, INT32 m_iSrcIndex, ArrayBase* m_pDst, INT32 m_iDstIndex, INT32 m_iLength, CLR_BOOL reliable);
-    static FCDECL3(void, ArrayClear, ArrayBase* pArrayUNSAFE, INT32 iIndex, INT32 iLength);
+
+    static FCDECL5(void*, GetRawArrayGeometry, ArrayBase* pArray, UINT32* pNumComponents, UINT32* pElementSize, INT32* pLowerBound, CLR_BOOL* pContainsGCPointers);
 
     // This method will create a new array of type type, with zero lower
     // bounds and rank.