Skip to content
Open
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
36 changes: 36 additions & 0 deletions clang/docs/HIPSupport.rst
Original file line number Diff line number Diff line change
Expand Up @@ -286,6 +286,42 @@ Example Usage
basePtr->virtualFunction(); // Allowed since obj is constructed in device code
}

Alias Attribute Support
=======================

Clang supports alias attributes in HIP code, allowing creation of alternative names for functions and variables.
- Aliases work with ``__host__``, ``__device__``, and ``__host__ __device__`` functions and variables.
- The alias attribute uses the syntax ``__attribute__((alias("target_name")))``. Both weak and strong aliases are supported.
- Outside of ``extern "C"``, the alias target must use the mangled name of the aliasee

Example Usage
-------------

.. code-block:: c++

extern "C" {
// Host function alias
int __HostFunc(void) { return 0; }
int HostFunc(void) __attribute__((weak, alias("__HostFunc")));

// Device function alias
__device__ int __DeviceFunc(void) { return 1; }
__device__ int DeviceFunc(void) __attribute__((weak, alias("__DeviceFunc")));

// Host-device function alias
__host__ __device__ int __BothFunc(void) { return 2; }
__host__ __device__ int BothFunc(void) __attribute__((alias("__BothFunc")));

// Variable alias
int __host_var = 3;
extern int __attribute__((weak, alias("__host_var"))) host_var;
}
// Mangled / overload alias
__host__ __device__ float __Four(float f) { return 2.0f * f; }
__host__ __device__ int Four(void) __attribute__((weak, alias("_Z6__Fourv")));
__host__ __device__ float Four(float f) __attribute__((weak, alias("_Z6__Fourf")));


Host and Device Attributes of Default Destructors
===================================================

Expand Down
37 changes: 36 additions & 1 deletion clang/lib/CodeGen/CodeGenModule.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -4043,6 +4043,38 @@ template <typename AttrT> static bool hasImplicitAttr(const ValueDecl *D) {
return D->isImplicit();
}

static bool shouldSkipAliasEmission(const CodeGenModule &CGM,
const ValueDecl *Global) {
const LangOptions &LangOpts = CGM.getLangOpts();
if (!LangOpts.OpenMPIsTargetDevice && !LangOpts.CUDA)
return false;

const auto *AA = Global->getAttr<AliasAttr>();
GlobalDecl AliaseeGD;

// Check if the aliasee exists, if the aliasee is not found, skip the alias
// emission. This is executed for both the host and device.
if (!CGM.lookupRepresentativeDecl(AA->getAliasee(), AliaseeGD))
return true;

const auto *AliaseeDecl = dyn_cast<ValueDecl>(AliaseeGD.getDecl());
if (LangOpts.OpenMPIsTargetDevice)
return !AliaseeDecl ||
!OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(AliaseeDecl);

// CUDA / HIP
const bool HasDeviceAttr = Global->hasAttr<CUDADeviceAttr>();
const bool AliaseeHasDeviceAttr =
AliaseeDecl && AliaseeDecl->hasAttr<CUDADeviceAttr>();

if (LangOpts.CUDAIsDevice)
return !HasDeviceAttr || !AliaseeHasDeviceAttr;

// CUDA / HIP Host
// we know that the aliasee exists from above, so we know to emit
return false;
}

bool CodeGenModule::shouldEmitCUDAGlobalVar(const VarDecl *Global) const {
assert(LangOpts.CUDA && "Should not be called by non-CUDA languages");
// We need to emit host-side 'shadows' for all global
Expand All @@ -4065,8 +4097,11 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) {

// If this is an alias definition (which otherwise looks like a declaration)
// emit it now.
if (Global->hasAttr<AliasAttr>())
if (Global->hasAttr<AliasAttr>()) {
if (shouldSkipAliasEmission(*this, Global))
return;
return EmitAliasDefinition(GD);
}

// IFunc like an alias whose value is resolved at runtime by calling resolver.
if (Global->hasAttr<IFuncAttr>())
Expand Down
17 changes: 17 additions & 0 deletions clang/test/CodeGenCUDA/cuda_weak_alias.cu
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-globals all --version 6
// RUN: %clang_cc1 -x cuda -triple x86_64-unknown-linux-gnu -aux-triple nvptx64-nvidia-cuda -emit-llvm %s -o - | FileCheck %s --check-prefix=HOST

extern "C" {

//.
// HOST: @HostFunc = weak alias i32 (), ptr @__HostFunc
//.
// HOST-LABEL: define dso_local i32 @__HostFunc(
// HOST-SAME: ) #[[ATTR0:[0-9]+]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 42
//
int __HostFunc(void) { return 42; }
int HostFunc(void) __attribute__ ((weak, alias("__HostFunc")));

}
125 changes: 125 additions & 0 deletions clang/test/CodeGenHIP/hip_weak_alias.cpp
Original file line number Diff line number Diff line change
@@ -0,0 +1,125 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-globals all --version 6
// REQUIRES: amdgpu-registered-target
// RUN: %clang_cc1 -x hip -triple x86_64-unknown-linux-gnu -aux-triple amdgcn-amd-amdhsa -emit-llvm-bc %s -o %t-host.bc
// RUN: %clang_cc1 -x hip -triple x86_64-unknown-linux-gnu -aux-triple amdgcn-amd-amdhsa -emit-llvm %s -o - | FileCheck %s --check-prefix=HOST
// RUN: %clang_cc1 -x hip -triple amdgcn-amd-amdhsa -aux-triple x86_64-unknown-linux-gnu -emit-llvm %s -fcuda-is-device -o - | FileCheck %s --check-prefix=DEVICE

#define __device__ __attribute__((device))
#define __host__ __attribute__((host))

extern "C" {
//.
// HOST: @HostFunc = weak alias i32 (), ptr @__HostFunc
// HOST: @HostFunc_ = alias i32 (), ptr @__HostFunc
// HOST: @HostVar = weak alias i32, ptr @__HostVar
// HOST: @HostVar_ = alias i32, ptr @__HostVar
// HOST: @Two = weak alias i32 (), ptr @__Two
// HOST: @Two_ = alias i32 (), ptr @__Two
// HOST: @_Z5Threev = weak alias i32 (), ptr @_Z7__Threev
// HOST: @_Z6Three_v = alias i32 (), ptr @_Z7__Threev
// HOST: @_Z4Fourv = weak alias i32 (), ptr @_Z6__Fourv
// HOST: @_Z4Fourf = weak alias float (float), ptr @_Z6__Fourf
//.
// DEVICE: @One = weak alias i32 (), ptr @__One
// DEVICE: @One_ = alias i32 (), ptr @__One
// DEVICE: @Two = weak alias i32 (), ptr @__Two
// DEVICE: @Two_ = alias i32 (), ptr @__Two
// DEVICE: @_Z5Threev = weak alias i32 (), ptr @_Z7__Threev
// DEVICE: @_Z6Three_v = alias i32 (), ptr @_Z7__Threev
// DEVICE: @_Z4Fourv = weak alias i32 (), ptr @_Z6__Fourv
// DEVICE: @_Z4Fourf = weak alias float (float), ptr @_Z6__Fourf
//.
// HOST-LABEL: define dso_local i32 @__HostFunc(
// HOST-SAME: ) #[[ATTR0:[0-9]+]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 42
//
int __HostFunc(void) { return 42; }
int __HostVar = 1;
int HostFunc(void) __attribute__((weak, alias("__HostFunc")));
int HostFunc_(void) __attribute__((alias("__HostFunc")));
extern int __attribute__((weak, alias("__HostVar"))) HostVar;
extern int __attribute__((alias("__HostVar"))) HostVar_;

// DEVICE-LABEL: define dso_local i32 @__One(
// DEVICE-SAME: ) #[[ATTR0:[0-9]+]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 1
//
__device__ int __One(void) { return 1; }
__device__ int One(void) __attribute__((weak, alias("__One")));
__device__ int One_(void) __attribute__((alias("__One")));

Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

can we add lit tests for:

  1. aliasee being a host device function
  2. aliasee being a constexpr function
  3. aliasee being one of an overloaded device functions aliased by mangled name

Copy link
Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I added the cases for HIP and amdgcn for OpenMP in 16c1a68,

The cases work without modification of the patch.

// HOST-LABEL: define dso_local i32 @__Two(
// HOST-SAME: ) #[[ATTR0]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 2
//
// DEVICE-LABEL: define dso_local i32 @__Two(
// DEVICE-SAME: ) #[[ATTR0]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 2
//
__host__ __device__ int __Two(void) { return 2; }
__host__ __device__ int Two(void) __attribute__((weak, alias("__Two")));
__host__ __device__ int Two_(void) __attribute__((alias("__Two")));
}

// HOST-LABEL: define linkonce_odr noundef i32 @_Z7__Threev(
// HOST-SAME: ) #[[ATTR0]] comdat {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 5
//
// DEVICE-LABEL: define linkonce_odr noundef i32 @_Z7__Threev(
// DEVICE-SAME: ) #[[ATTR0]] comdat {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 5
//
__host__ __device__ constexpr int __Three(void) { return 5; }
__host__ __device__ int Three(void) __attribute__((weak, alias("_Z7__Threev")));
__host__ __device__ int Three_(void) __attribute__((alias("_Z7__Threev")));


// HOST-LABEL: define dso_local noundef i32 @_Z6__Fourv(
// HOST-SAME: ) #[[ATTR0]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 2
//
// DEVICE-LABEL: define dso_local noundef i32 @_Z6__Fourv(
// DEVICE-SAME: ) #[[ATTR0]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 2
//
__host__ __device__ int __Four(void) { return 2; }
// HOST-LABEL: define dso_local noundef float @_Z6__Fourf(
// HOST-SAME: float noundef [[F:%.*]]) #[[ATTR0]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: [[F_ADDR:%.*]] = alloca float, align 4
// HOST-NEXT: store float [[F]], ptr [[F_ADDR]], align 4
// HOST-NEXT: [[TMP0:%.*]] = load float, ptr [[F_ADDR]], align 4
// HOST-NEXT: [[MUL:%.*]] = fmul contract float 2.000000e+00, [[TMP0]]
// HOST-NEXT: ret float [[MUL]]
//
// DEVICE-LABEL: define dso_local noundef float @_Z6__Fourf(
// DEVICE-SAME: float noundef [[F:%.*]]) #[[ATTR0]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca float, align 4, addrspace(5)
// DEVICE-NEXT: [[F_ADDR:%.*]] = alloca float, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: [[F_ADDR_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[F_ADDR]] to ptr
// DEVICE-NEXT: store float [[F]], ptr [[F_ADDR_ASCAST]], align 4
// DEVICE-NEXT: [[TMP0:%.*]] = load float, ptr [[F_ADDR_ASCAST]], align 4
// DEVICE-NEXT: [[MUL:%.*]] = fmul contract float 2.000000e+00, [[TMP0]]
// DEVICE-NEXT: ret float [[MUL]]
//
__host__ __device__ float __Four(float f) { return 2.0f * f; }
__host__ __device__ int Four(void) __attribute__((weak, alias("_Z6__Fourv")));
__host__ __device__ float Four(float f) __attribute__((weak, alias("_Z6__Fourf")));
103 changes: 103 additions & 0 deletions clang/test/OpenMP/amdgcn_weak_alias.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,103 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --check-globals all --version 6
// REQUIRES: amdgpu-registered-target

// RUN: %clang_cc1 -fopenmp -x c -triple x86_64-unknown-unknown -fopenmp-targets=amdgcn-amd-amdhsa -emit-llvm-bc %s -o %t-ppc-host.bc
// RUN: %clang_cc1 -fopenmp -x c -triple x86_64-unknown-unknown -fopenmp-targets=amdgcn-amd-amdhsa -emit-llvm %s -o - | FileCheck %s --check-prefix=HOST
// RUN: %clang_cc1 -fopenmp -x c -triple amdgcn-amd-amdhsa -fopenmp-targets=amdgcn-amd-amdhsa -emit-llvm %s -fopenmp-is-target-device -fopenmp-host-ir-file-path %t-ppc-host.bc -o - | FileCheck %s --check-prefix=DEVICE

//.
// HOST: @__One_var = global i32 1, align 4
// HOST: @__Two_var = global i32 2, align 4
// HOST: @__Three_var = global i32 3, align 4
// HOST: @.offloading.entry_name = internal unnamed_addr constant [10 x i8] c"__Two_var\00", section ".llvm.rodata.offloading", align 1
// HOST: @.offloading.entry.__Two_var = weak constant %struct.__tgt_offload_entry { i64 0, i16 1, i16 1, i32 0, ptr @__Two_var, ptr @.offloading.entry_name, i64 4, i64 0, ptr null }, section "llvm_offload_entries", align 8
// HOST: @.offloading.entry_name.1 = internal unnamed_addr constant [12 x i8] c"__Three_var\00", section ".llvm.rodata.offloading", align 1
// HOST: @.offloading.entry.__Three_var = weak constant %struct.__tgt_offload_entry { i64 0, i16 1, i16 1, i32 0, ptr @__Three_var, ptr @.offloading.entry_name.1, i64 4, i64 0, ptr null }, section "llvm_offload_entries", align 8
// HOST: @One = weak alias i32 (), ptr @__One
// HOST: @One_ = alias i32 (), ptr @__One
// HOST: @One_var = weak alias i32, ptr @__One_var
// HOST: @One_var_ = alias i32, ptr @__One_var
// HOST: @Two = weak alias i32 (), ptr @__Two
// HOST: @Two_ = alias i32 (), ptr @__Two
// HOST: @Two_var = weak alias i32, ptr @__Two_var
// HOST: @Two_var_ = alias i32, ptr @__Two_var
// HOST: @Three = weak alias i32 (), ptr @__Three
// HOST: @Three_ = alias i32 (), ptr @__Three
// HOST: @Three_var = weak alias i32, ptr @__Three_var
// HOST: @Three_var_ = alias i32, ptr @__Three_var
//.
// DEVICE: @__Two_var = addrspace(1) global i32 2, align 4
// DEVICE: @__Three_var = addrspace(1) global i32 3, align 4
// DEVICE: @Two = weak hidden alias i32 (), ptr @__Two
// DEVICE: @Two_ = hidden alias i32 (), ptr @__Two
// DEVICE: @Two_var = weak alias i32, addrspacecast (ptr addrspace(1) @__Two_var to ptr)
// DEVICE: @Two_var_ = alias i32, addrspacecast (ptr addrspace(1) @__Two_var to ptr)
// DEVICE: @Three = weak hidden alias i32 (), ptr @__Three
// DEVICE: @Three.1 = weak hidden alias i32 (), ptr @__Three
// DEVICE: @Three_ = hidden alias i32 (), ptr @__Three
// DEVICE: @Three_.2 = hidden alias i32 (), ptr @__Three
// DEVICE: @Three_var = weak alias i32, addrspacecast (ptr addrspace(1) @__Three_var to ptr)
// DEVICE: @Three_var_ = alias i32, addrspacecast (ptr addrspace(1) @__Three_var to ptr)
//.
// HOST-LABEL: define dso_local i32 @__One(
// HOST-SAME: ) #[[ATTR0:[0-9]+]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 1
//
int __One(void) { return 1; }
int One(void) __attribute__ ((weak, alias("__One")));
int One_(void) __attribute__ ((alias("__One")));

int __One_var = 1;
extern int __attribute__((weak, alias("__One_var"))) One_var;
extern int __attribute__((alias("__One_var"))) One_var_;

#pragma omp declare target
// HOST-LABEL: define dso_local i32 @__Two(
// HOST-SAME: ) #[[ATTR0]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 2
//
// DEVICE-LABEL: define hidden i32 @__Two(
// DEVICE-SAME: ) #[[ATTR0:[0-9]+]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 2
//
int __Two(void) { return 2; }
int Two(void) __attribute__ ((weak, alias("__Two")));
int Two_(void) __attribute__ ((alias("__Two")));

int __Two_var = 2;
extern int __attribute__((weak, alias("__Two_var"))) Two_var;
extern int __attribute__((alias("__Two_var"))) Two_var_;
#pragma omp end declare target

#pragma omp declare target
// HOST-LABEL: define dso_local i32 @__Three(
// HOST-SAME: ) #[[ATTR0]] {
// HOST-NEXT: [[ENTRY:.*:]]
// HOST-NEXT: ret i32 3
//
// DEVICE-LABEL: define hidden i32 @__Three(
// DEVICE-SAME: ) #[[ATTR0]] {
// DEVICE-NEXT: [[ENTRY:.*:]]
// DEVICE-NEXT: [[RETVAL:%.*]] = alloca i32, align 4, addrspace(5)
// DEVICE-NEXT: [[RETVAL_ASCAST:%.*]] = addrspacecast ptr addrspace(5) [[RETVAL]] to ptr
// DEVICE-NEXT: ret i32 3
//
int __Three(void) { return 3; }
int __Three_var = 3;
#pragma omp end declare target
int Three(void) __attribute__ ((weak, alias("__Three")));
int Three_(void) __attribute__ ((alias("__Three")));
extern int __attribute__((weak, alias("__Three_var"))) Three_var;
extern int __attribute__((alias("__Three_var"))) Three_var_;
//.
// HOST: [[META0:![0-9]+]] = !{i32 1, !"__Two_var", i32 0, i32 0}
// HOST: [[META1:![0-9]+]] = !{i32 1, !"__Three_var", i32 0, i32 1}
//.
// DEVICE: [[META0:![0-9]+]] = !{i32 1, !"__Two_var", i32 0, i32 0}
// DEVICE: [[META1:![0-9]+]] = !{i32 1, !"__Three_var", i32 0, i32 1}
//.
Loading