[HIP] Make __hip_gpubin_handle hidden to avoid being merged across different shared libraries

[yaxunl]

Summary

Different shared libraries contain different fat binary, which is stored in a global variable
__hip_gpubin_handle. Since different compilation units share the same fat binary, this
variable has linkonce linkage. However, it should not be merged across different shared
libraries.

This patch set the visibility of the global variable to be hidden, which will make it invisible
in the shared library, therefore preventing it from being merged.

lib/CodeGen/CGCUDANV.cpp

if (IsHIP) {
     // The name, size, and initialization pattern of this variable is part
     // of HIP ABI.
     GpuBinaryHandle = new llvm::GlobalVariable(
         TheModule, VoidPtrPtrTy, /*isConstant=*/false,
         llvm::GlobalValue::LinkOnceAnyLinkage,
         /*Initializer=*/llvm::ConstantPointerNull::get(VoidPtrPtrTy),
         "__hip_gpubin_handle");
     GpuBinaryHandle->setAlignment(CGM.getPointerAlign().getQuantity());
+    // Prevent the weak symbol in different shared libraries being merged.
+    GpuBinaryHandle->setVisibility(llvm::GlobalValue::HiddenVisibility);
     Address GpuBinaryAddr(
         GpuBinaryHandle,
         CharUnits::fromQuantity(GpuBinaryHandle->getAlignment()));
     {
       auto HandleValue = CtorBuilder.CreateLoad(GpuBinaryAddr);
       llvm::Constant *Zero =
           llvm::Constant::getNullValue(HandleValue->getType());
       llvm::Value *EQZero = CtorBuilder.CreateICmpEQ(HandleValue, Zero);

test/CodeGenCUDA/device-stub.cu

 // HIP-SAME: { i32 1212764230, i32 1,
 // CUDA-SAME: i8* getelementptr inbounds ({{.*}}@[[FATBIN]], i64 0, i64 0),
 // HIP-SAME:  i8* @[[FATBIN]],
 // ALL-SAME: i8* null }
 // CUDA-SAME: section ".nvFatBinSegment"
 // HIP-SAME: section ".hipFatBinSegment"
 // * variable to save GPU binary handle after initialization
 // CUDANORDC: @__[[PREFIX]]_gpubin_handle = internal global i8** null
-// HIP: @__[[PREFIX]]_gpubin_handle = linkonce global i8** null
+// HIP: @__[[PREFIX]]_gpubin_handle = linkonce hidden global i8** null
 // * constant unnamed string with NVModuleID
 // RDC: [[MODULE_ID_GLOBAL:@.*]] = private constant
 // CUDARDC-SAME: c"[[MODULE_ID:.+]]\00", section "__nv_module_id", align 32
 // * Make sure our constructor was added to global ctor list.
 // ALL: @llvm.global_ctors = appending global {{.*}}@__[[PREFIX]]_module_ctor
 // * Alias to global symbol containing the NVModuleID.
 // RDC: @__fatbinwrap[[MODULE_ID]] = alias { i32, i32, i8*, i8* }
 // RDC-SAME: { i32, i32, i8*, i8* }* @__[[PREFIX]]_fatbin_wrapper