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[libc] Export a pointer to the RPC client directly #117913

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Merged
merged 1 commit into from
Nov 27, 2024
Merged

[libc] Export a pointer to the RPC client directly #117913

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12 changes: 4 additions & 8 deletions libc/src/__support/RPC/rpc_client.cpp
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Expand Up @@ -13,14 +13,10 @@
namespace LIBC_NAMESPACE_DECL {
namespace rpc {

/// The libc client instance used to communicate with the server.
Client client;

/// Externally visible symbol to signify the usage of an RPC client to
/// whomever needs to run the server as well as provide a way to initialize
/// the client with a copy..
extern "C" [[gnu::visibility("protected")]] const void *__llvm_libc_rpc_client =
&client;
/// The libc client instance used to communicate with the server. Externally
/// visible symbol to signify the usage of an RPC client to whomever needs to
/// run the server as well as provide a way to initialize the client.
[[gnu::visibility("protected")]] Client client;

} // namespace rpc
} // namespace LIBC_NAMESPACE_DECL
2 changes: 1 addition & 1 deletion libc/src/__support/RPC/rpc_client.h
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Expand Up @@ -29,7 +29,7 @@ static_assert(cpp::is_trivially_copyable<Client>::value &&
"The client is not trivially copyable from the server");

/// The libc client instance used to communicate with the server.
extern Client client;
[[gnu::visibility("protected")]] extern Client client asm("__llvm_rpc_client");
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@shiltian shiltian Nov 27, 2024

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do we have any policy about this kind of use?

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@jhuber6 jhuber6 Nov 27, 2024

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Policy? It's standard ELF visibility rules that if you want something to be readable from the GPU runtime it can't have hidden visibility.

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@shiltian shiltian Nov 27, 2024

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I meant using asm to rename a variable.

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@jhuber6 jhuber6 Nov 27, 2024

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I don't know, but it's already how we export the libc functions themselves in the libc project so it's nothing new there. It's like

namespace LIBC_NAMESPACE {
  void foo() __asm__("foo");
}


} // namespace rpc
} // namespace LIBC_NAMESPACE_DECL
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20 changes: 3 additions & 17 deletions libc/utils/gpu/loader/amdgpu/amdhsa-loader.cpp
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Expand Up @@ -477,27 +477,15 @@ int load(int argc, const char **argv, const char **envp, void *image,
// device's internal pointer.
hsa_executable_symbol_t rpc_client_sym;
if (hsa_status_t err = hsa_executable_get_symbol_by_name(
executable, "__llvm_libc_rpc_client", &dev_agent, &rpc_client_sym))
executable, "__llvm_rpc_client", &dev_agent, &rpc_client_sym))
handle_error(err);

void *rpc_client_host;
if (hsa_status_t err =
hsa_amd_memory_pool_allocate(finegrained_pool, sizeof(void *),
/*flags=*/0, &rpc_client_host))
handle_error(err);
hsa_amd_agents_allow_access(1, &dev_agent, nullptr, rpc_client_host);

void *rpc_client_dev;
if (hsa_status_t err = hsa_executable_symbol_get_info(
rpc_client_sym, HSA_EXECUTABLE_SYMBOL_INFO_VARIABLE_ADDRESS,
&rpc_client_dev))
handle_error(err);

// Copy the address of the client buffer from the device to the host.
if (hsa_status_t err = hsa_memcpy(rpc_client_host, host_agent, rpc_client_dev,
dev_agent, sizeof(void *)))
handle_error(err);

void *rpc_client_buffer;
if (hsa_status_t err =
hsa_amd_memory_lock(&client, sizeof(rpc::Client),
Expand All @@ -506,14 +494,12 @@ int load(int argc, const char **argv, const char **envp, void *image,

// Copy the RPC client buffer to the address pointed to by the symbol.
if (hsa_status_t err =
hsa_memcpy(*reinterpret_cast<void **>(rpc_client_host), dev_agent,
rpc_client_buffer, host_agent, sizeof(rpc::Client)))
hsa_memcpy(rpc_client_dev, dev_agent, rpc_client_buffer, host_agent,
sizeof(rpc::Client)))
handle_error(err);

if (hsa_status_t err = hsa_amd_memory_unlock(&client))
handle_error(err);
if (hsa_status_t err = hsa_amd_memory_pool_free(rpc_client_host))
handle_error(err);

// Obtain the GPU's fixed-frequency clock rate and copy it to the GPU.
// If the clock_freq symbol is missing, no work to do.
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9 changes: 2 additions & 7 deletions libc/utils/gpu/loader/nvptx/nvptx-loader.cpp
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Expand Up @@ -314,15 +314,10 @@ int load(int argc, const char **argv, const char **envp, void *image,
CUdeviceptr rpc_client_dev = 0;
uint64_t client_ptr_size = sizeof(void *);
if (CUresult err = cuModuleGetGlobal(&rpc_client_dev, &client_ptr_size,
binary, "__llvm_libc_rpc_client"))
binary, "__llvm_rpc_client"))
handle_error(err);

CUdeviceptr rpc_client_host = 0;
if (CUresult err =
cuMemcpyDtoH(&rpc_client_host, rpc_client_dev, sizeof(void *)))
handle_error(err);
if (CUresult err =
cuMemcpyHtoD(rpc_client_host, &client, sizeof(rpc::Client)))
if (CUresult err = cuMemcpyHtoD(rpc_client_dev, &client, sizeof(rpc::Client)))
handle_error(err);

LaunchParameters single_threaded_params = {1, 1, 1, 1, 1, 1};
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2 changes: 1 addition & 1 deletion llvm/lib/Transforms/IPO/OpenMPOpt.cpp
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Expand Up @@ -1538,7 +1538,7 @@ struct OpenMPOpt {
// required an RPC server. If its users were all optimized out then we can
// safely remove it.
// TODO: This should be somewhere more common in the future.
if (GlobalVariable *GV = M.getNamedGlobal("__llvm_libc_rpc_client")) {
if (GlobalVariable *GV = M.getNamedGlobal("__llvm_rpc_client")) {
if (!GV->getType()->isPointerTy())
return false;

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6 changes: 3 additions & 3 deletions llvm/test/Transforms/OpenMP/keep_rpc_client.ll
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Expand Up @@ -3,14 +3,14 @@
; RUN: opt -S -passes=openmp-opt < %s | FileCheck %s --check-prefix=PRELINK

@client = internal addrspace(1) global i64 zeroinitializer, align 8
@__llvm_libc_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
@__llvm_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8

;.
; POSTLINK: @client = internal addrspace(1) global i64 0, align 8
; POSTLINK: @__llvm_libc_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
; POSTLINK: @__llvm_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
;.
; PRELINK: @client = internal addrspace(1) global i64 0, align 8
; PRELINK: @__llvm_libc_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
; PRELINK: @__llvm_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
;.
define i64 @a() {
; POSTLINK-LABEL: define {{[^@]+}}@a
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4 changes: 2 additions & 2 deletions llvm/test/Transforms/OpenMP/remove_rpc_client.ll
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Expand Up @@ -3,11 +3,11 @@
; RUN: opt -S -passes=openmp-opt < %s | FileCheck %s --check-prefix=PRELINK

@client = internal addrspace(1) global i32 zeroinitializer, align 8
@__llvm_libc_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
@__llvm_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8

;.
; PRELINK: @client = internal addrspace(1) global i32 0, align 8
; PRELINK: @__llvm_libc_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
; PRELINK: @__llvm_rpc_client = protected local_unnamed_addr addrspace(1) global ptr addrspacecast (ptr addrspace(1) @client to ptr), align 8
;.
define void @a() {
; POSTLINK-LABEL: define {{[^@]+}}@a() {
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13 changes: 4 additions & 9 deletions offload/plugins-nextgen/common/src/RPC.cpp
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Expand Up @@ -31,7 +31,7 @@ RPCServerTy::isDeviceUsingRPC(plugin::GenericDeviceTy &Device,
plugin::GenericGlobalHandlerTy &Handler,
plugin::DeviceImageTy &Image) {
#ifdef LIBOMPTARGET_RPC_SUPPORT
return Handler.isSymbolInImage(Device, Image, "__llvm_libc_rpc_client");
return Handler.isSymbolInImage(Device, Image, "__llvm_rpc_client");
#else
return false;
#endif
Expand All @@ -51,19 +51,14 @@ Error RPCServerTy::initDevice(plugin::GenericDeviceTy &Device,
"Failed to initialize RPC server for device %d", Device.getDeviceId());

// Get the address of the RPC client from the device.
void *ClientPtr;
plugin::GlobalTy ClientGlobal("__llvm_libc_rpc_client", sizeof(void *));
plugin::GlobalTy ClientGlobal("__llvm_rpc_client", sizeof(rpc::Client));
if (auto Err =
Handler.getGlobalMetadataFromDevice(Device, Image, ClientGlobal))
return Err;

if (auto Err = Device.dataRetrieve(&ClientPtr, ClientGlobal.getPtr(),
sizeof(void *), nullptr))
return Err;

rpc::Client client(NumPorts, RPCBuffer);
if (auto Err =
Device.dataSubmit(ClientPtr, &client, sizeof(rpc::Client), nullptr))
if (auto Err = Device.dataSubmit(ClientGlobal.getPtr(), &client,
sizeof(rpc::Client), nullptr))
return Err;
Buffers[Device.getDeviceId()] = RPCBuffer;

Expand Down