Fold "cns"[cns] for ROS<char> (#78593)

Co-authored-by: SingleAccretion <62474226+SingleAccretion@users.noreply.github.com>

src/coreclr/inc/corinfo.h

@@ -2496,6 +2496,23 @@ class ICorStaticInfo
             CORINFO_OBJECT_HANDLE       objPtr
             ) = 0;
 
+    //------------------------------------------------------------------------------
+    // getStringChar: returns char at the given index if the given object handle
+    //    represents String and index is not out of bounds.
+    //
+    // Arguments:
+    //    strObj - object handle
+    //    index  - index of the char to return
+    //    value  - output char
+    //
+    // Return Value:
+    //    Returns true if value was successfully obtained
+    //
+    virtual bool getStringChar(
+            CORINFO_OBJECT_HANDLE strObj,
+            int                   index,
+            uint16_t*             value) = 0;
+
     //------------------------------------------------------------------------------
     // getObjectType: obtains type handle for given object
     //

src/coreclr/inc/icorjitinfoimpl_generated.h

@@ -288,6 +288,11 @@ CORINFO_OBJECT_HANDLE getRuntimeTypePointer(
 bool isObjectImmutable(
           CORINFO_OBJECT_HANDLE objPtr) override;
 
+bool getStringChar(
+          CORINFO_OBJECT_HANDLE strObj,
+          int index,
+          uint16_t* value) override;
+
 CORINFO_CLASS_HANDLE getObjectType(
           CORINFO_OBJECT_HANDLE objPtr) override;
 

src/coreclr/inc/jiteeversionguid.h

@@ -43,11 +43,11 @@ typedef const GUID *LPCGUID;
 #define GUID_DEFINED
 #endif // !GUID_DEFINED
 
-constexpr GUID JITEEVersionIdentifier = { /* 1e794e80-ec63-4d7a-b11f-fcda6e7fe4f4 */
-    0x1e794e80,
-    0xec63,
-    0x4d7a,
-    {0xb1, 0x1f, 0xfc, 0xda, 0x6e, 0x7f, 0xe4, 0xf4}
+constexpr GUID JITEEVersionIdentifier = { /* da097b39-7f43-458a-990a-0b65406d5ff3 */
+    0xda097b39,
+    0x7f43,
+    0x458a,
+    {0x99, 0xa, 0xb, 0x65, 0x40, 0x6d, 0x5f, 0xf3}
   };
 
 //////////////////////////////////////////////////////////////////////////////////////////////////////////

src/coreclr/jit/ICorJitInfo_names_generated.h

@@ -72,6 +72,7 @@ DEF_CLR_API(getBoxHelper)
 DEF_CLR_API(getUnBoxHelper)
 DEF_CLR_API(getRuntimeTypePointer)
 DEF_CLR_API(isObjectImmutable)
+DEF_CLR_API(getStringChar)
 DEF_CLR_API(getObjectType)
 DEF_CLR_API(getReadyToRunHelper)
 DEF_CLR_API(getReadyToRunDelegateCtorHelper)

src/coreclr/jit/ICorJitInfo_wrapper_generated.hpp

@@ -672,6 +672,17 @@ bool WrapICorJitInfo::isObjectImmutable(
     return temp;
 }
 
+bool WrapICorJitInfo::getStringChar(
+          CORINFO_OBJECT_HANDLE strObj,
+          int index,
+          uint16_t* value)
+{
+    API_ENTER(getStringChar);
+    bool temp = wrapHnd->getStringChar(strObj, index, value);
+    API_LEAVE(getStringChar);
+    return temp;
+}
+
 CORINFO_CLASS_HANDLE WrapICorJitInfo::getObjectType(
           CORINFO_OBJECT_HANDLE objPtr)
 {

src/coreclr/jit/compiler.h

@@ -4833,6 +4833,8 @@ class Compiler
     void fgValueNumberFieldStore(
         GenTree* storeNode, GenTree* baseAddr, FieldSeq* fieldSeq, ssize_t offset, unsigned storeSize, ValueNum value);
 
+    bool fgValueNumberConstLoad(GenTreeIndir* tree);
+
     // Compute the value number for a byref-exposed load of the given type via the given pointerVN.
     ValueNum fgValueNumberByrefExposedLoad(var_types type, ValueNum pointerVN);
 

src/coreclr/jit/jit.h

@@ -330,6 +330,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 
 typedef class ICorJitInfo* COMP_HANDLE;
 
+const CORINFO_OBJECT_HANDLE NO_OBJECT_HANDLE = nullptr;
 const CORINFO_CLASS_HANDLE  NO_CLASS_HANDLE  = nullptr;
 const CORINFO_FIELD_HANDLE  NO_FIELD_HANDLE  = nullptr;
 const CORINFO_METHOD_HANDLE NO_METHOD_HANDLE = nullptr;

src/coreclr/jit/valuenum.cpp

@@ -8494,6 +8494,103 @@ void Compiler::fgValueNumberSsaVarDef(GenTreeLclVarCommon* lcl)
     }
 }
 
+//----------------------------------------------------------------------------------
+// fgValueNumberConstLoad: Try to detect const_immutable_array[cns_index] tree
+//    and apply a constant VN representing given element at cns_index in that array.
+//
+// Arguments:
+//    tree - the GT_IND node
+//
+// Return Value:
+//    true if the pattern was recognized and a new VN is assigned
+//
+bool Compiler::fgValueNumberConstLoad(GenTreeIndir* tree)
+{
+    ValueNum  addrVN = tree->gtGetOp1()->gtVNPair.GetLiberal();
+    VNFuncApp funcApp;
+    if (!tree->TypeIs(TYP_USHORT) || !tree->gtVNPair.BothEqual() || !vnStore->GetVNFunc(addrVN, &funcApp))
+    {
+        return false;
+    }
+
+    // Is given VN representing a frozen object handle
+    auto isCnsObjHandle = [](ValueNumStore* vnStore, ValueNum vn, CORINFO_OBJECT_HANDLE* handle) -> bool {
+        if (vnStore->IsVNHandle(vn) && (vnStore->GetHandleFlags(vn) == GTF_ICON_OBJ_HDL))
+        {
+            const size_t obj = vnStore->CoercedConstantValue<size_t>(vn);
+            *handle          = reinterpret_cast<CORINFO_OBJECT_HANDLE>(obj);
+            return true;
+        }
+        return false;
+    };
+
+    CORINFO_OBJECT_HANDLE objHandle = NO_OBJECT_HANDLE;
+    size_t                index     = -1;
+
+    // First, let see if we have PtrToArrElem
+    ValueNum addr = funcApp.m_args[0];
+    if (funcApp.m_func == VNF_PtrToArrElem)
+    {
+        ValueNum arrVN  = funcApp.m_args[1];
+        ValueNum inxVN  = funcApp.m_args[2];
+        ssize_t  offset = vnStore->ConstantValue<ssize_t>(funcApp.m_args[3]);
+
+        if (isCnsObjHandle(vnStore, arrVN, &objHandle) && (offset == 0) && vnStore->IsVNConstant(inxVN))
+        {
+            index = vnStore->CoercedConstantValue<size_t>(inxVN);
+        }
+    }
+    else if (funcApp.m_func == (VNFunc)GT_ADD)
+    {
+        ssize_t  dataOffset = 0;
+        ValueNum baseVN     = ValueNumStore::NoVN;
+
+        // Loop to accumulate total dataOffset, e.g.:
+        // ADD(C1, ADD(ObjHandle, C2)) -> C1 + C2
+        do
+        {
+            ValueNum op1VN = funcApp.m_args[0];
+            ValueNum op2VN = funcApp.m_args[1];
+
+            if (vnStore->IsVNConstant(op1VN) && varTypeIsIntegral(vnStore->TypeOfVN(op1VN)) &&
+                !isCnsObjHandle(vnStore, op1VN, &objHandle))
+            {
+                dataOffset += vnStore->CoercedConstantValue<ssize_t>(op1VN);
+                baseVN = op2VN;
+            }
+            else if (vnStore->IsVNConstant(op2VN) && varTypeIsIntegral(vnStore->TypeOfVN(op2VN)) &&
+                     !isCnsObjHandle(vnStore, op2VN, &objHandle))
+            {
+                dataOffset += vnStore->CoercedConstantValue<ssize_t>(op2VN);
+                baseVN = op1VN;
+            }
+            else
+            {
+                // one of the args is expected to be an integer constant
+                return false;
+            }
+        } while (vnStore->GetVNFunc(baseVN, &funcApp) && (funcApp.m_func == (VNFunc)GT_ADD));
+
+        if (isCnsObjHandle(vnStore, baseVN, &objHandle) && (dataOffset >= (ssize_t)OFFSETOF__CORINFO_String__chars) &&
+            ((dataOffset % 2) == 0))
+        {
+            static_assert_no_msg((OFFSETOF__CORINFO_String__chars % 2) == 0);
+            index = (dataOffset - OFFSETOF__CORINFO_String__chars) / 2;
+        }
+    }
+
+    USHORT charValue;
+    if (((size_t)index < INT_MAX) && (objHandle != NO_OBJECT_HANDLE) &&
+        info.compCompHnd->getStringChar(objHandle, (int)index, &charValue))
+    {
+        JITDUMP("Folding \"cns_str\"[%d] into %u", (int)index, (unsigned)charValue);
+
+        tree->gtVNPair.SetBoth(vnStore->VNForIntCon(charValue));
+        return true;
+    }
+    return false;
+}
+
 void Compiler::fgValueNumberTree(GenTree* tree)
 {
     genTreeOps oper = tree->OperGet();
@@ -8745,6 +8842,10 @@ void Compiler::fgValueNumberTree(GenTree* tree)
                     // Note VNF_PtrToStatic statics are currently always "simple".
                     fgValueNumberFieldLoad(tree, /* baseAddr */ nullptr, fldSeq, offset);
                 }
+                else if (tree->OperIs(GT_IND) && fgValueNumberConstLoad(tree->AsIndir()))
+                {
+                    // VN is assigned inside fgValueNumberConstLoad
+                }
                 else if (vnStore->GetVNFunc(addrNvnp.GetLiberal(), &funcApp) && (funcApp.m_func == VNF_PtrToArrElem))
                 {
                     fgValueNumberArrayElemLoad(tree, &funcApp);
@@ -10502,6 +10603,12 @@ void Compiler::fgValueNumberAddExceptionSetForIndirection(GenTree* tree, GenTree
     // We should have tree that a unary indirection or a tree node with an implicit indirection
     assert(tree->OperIsUnary() || tree->OperIsImplicitIndir());
 
+    // if this indirection can be folded into a constant it means it can't trigger NullRef
+    if (tree->gtVNPair.BothEqual() && vnStore->IsVNConstant(tree->gtVNPair.GetLiberal()))
+    {
+        return;
+    }
+
     // We evaluate the baseAddr ValueNumber further in order
     // to obtain a better value to use for the null check exception.
     //