Handle addrspacecast of Null in ConstantEncoder

This change adds a safe handling path for addrspacecast of a Null pointer
in ConstantEncoder. Previously, such case triggered a diagnostic error
even though the semantic value is equivalent to a plain Null in the
destination address space.

Author: varev-dev

IGC/VectorCompiler/lib/GenXCodeGen/ConstantEncoder.cpp

@@ -76,8 +76,14 @@ encodeConstExprImpl(const IGCLLVM::AddrSpaceCastOperator &ASC,
                     const DataLayout &DL) {
   IGC_ASSERT_MESSAGE(!isa<IGCLLVM::FixedVectorType>(ASC.getType()),
                      "vector addrspacecast is not yet supported");
-  auto [Data, Relocs] = vc::encodeGlobalValueOrConstantExpression(
-      *cast<Constant>(ASC.getPointerOperand()), DL);
+  auto *OpC = cast<Constant>(ASC.getPointerOperand());
+
+  if (OpC->isNullValue()) {
+    const auto DstBits = vc::getTypeSize(ASC.getType(), &DL).inBits();
+    return {APInt(DstBits, 0), {}};
+  }
+
+  auto [Data, Relocs] = vc::encodeGlobalValueOrConstantExpression(*OpC, DL);
 
   // FIXME: p3 to p4 cast should also be part of this case if we consider
   //        p3 higher bits are marked from the beginning. Alternatively those

IGC/VectorCompiler/test/OCLRuntimeInfo/gv_addrspacecast_null.ll

@@ -0,0 +1,28 @@
+;=========================== begin_copyright_notice ============================
+;
+; Copyright (C) 2021-2025 Intel Corporation
+;
+; SPDX-License-Identifier: MIT
+;
+;============================ end_copyright_notice =============================
+
+
+; RUN: %llc_opaque_ptrs %s -march=genx64 -mcpu=Gen9 -mattr=+ocl_runtime -vc-analyze=GenXOCLRuntimeInfo \
+; RUN: -vc-choose-pass-manager-override=false -o /dev/null 2>&1 | FileCheck %s --check-prefixes=CHECK
+
+target datalayout = "e-p:64:64-i64:64-n8:16:32"
+target triple = "spir64-unknown-unknown"
+
+; CHECK: Printing analysis 'GenXOCLRuntimeInfo':
+
+; CHECK: Global:
+; CHECK: Data:
+; CHECK: Buffer: [
+@global.casted_null = addrspace(1) global ptr addrspace(1) addrspacecast (ptr addrspace(4) null to ptr addrspace(1)), align 8
+; CHECK-COUNT-7: 0,
+; CHECK-SAME: 0 ]
+; CHECK: Symbols:
+; CHECK-NEXT: - s_type:   S_GLOBAL_VAR
+; CHECK-NEXT:   s_offset: 0
+; CHECK-NEXT:   s_size:   8
+; CHECK-NEXT:   s_name:   global.casted_null