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Jason-VanBeusekom丹治秀樹
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[OpenMP][clang] Register vtables on device for indirect calls runtime (llvm#167011)
This is a branch off of llvm#159856, in which consists of the runtime portion of the changes required to support indirect function and virtual function calls on an `omp target device` when the virtual class / indirect function is mapped to the device from the host. Key Changes - Introduced a new flag OMP_DECLARE_TARGET_INDIRECT_VTABLE to mark VTable registrations - Modified setupIndirectCallTable to support both VTable entries and indirect function pointers Details: The setupIndirectCallTable implementation was modified to support this registration type by retrieving the first address of the VTable and inferring the remaining data needed to build the indirect call table. Since the Vtables / Classes registered as indirect can be larger than 8 bytes, and the vtables may not be at the first address we either need to pass the size to __llvm_omp_indirect_call_lookup and have a check at each step of the binary search, or add multiple entries to the indirect table for each address registered. The latter was chosen. Commit: a00def3 is not a part of this PR and is handled / reviewed in: llvm#159856, This is PR (2/3) Register Vtable PR (1/3): llvm#159856, Codegen / _llvm_omp_indirect_call_lookup PR (3/3): llvm#159857
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‎offload/include/omptarget.h‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -94,6 +94,8 @@ enum OpenMPOffloadingDeclareTargetFlags {
9494
OMP_DECLARE_TARGET_INDIRECT = 0x08,
9595
/// This is an entry corresponding to a requirement to be registered.
9696
OMP_REGISTER_REQUIRES = 0x10,
97+
/// Mark the entry global as being an indirect vtable.
98+
OMP_DECLARE_TARGET_INDIRECT_VTABLE = 0x20,
9799
};
98100

99101
enum TargetAllocTy : int32_t {

‎offload/libomptarget/PluginManager.cpp‎

Lines changed: 8 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -437,20 +437,22 @@ static int loadImagesOntoDevice(DeviceTy &Device) {
437437

438438
llvm::offloading::EntryTy DeviceEntry = Entry;
439439
if (Entry.Size) {
440-
if (Device.RTL->get_global(Binary, Entry.Size, Entry.SymbolName,
441-
&DeviceEntry.Address) != OFFLOAD_SUCCESS)
442-
REPORT("Failed to load symbol %s\n", Entry.SymbolName);
440+
if (!(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT_VTABLE))
441+
if (Device.RTL->get_global(Binary, Entry.Size, Entry.SymbolName,
442+
&DeviceEntry.Address) != OFFLOAD_SUCCESS)
443+
REPORT("Failed to load symbol %s\n", Entry.SymbolName);
443444

444445
// If unified memory is active, the corresponding global is a device
445446
// reference to the host global. We need to initialize the pointer on
446447
// the device to point to the memory on the host.
447-
if ((PM->getRequirements() & OMP_REQ_UNIFIED_SHARED_MEMORY) ||
448-
(PM->getRequirements() & OMPX_REQ_AUTO_ZERO_COPY)) {
448+
if (!(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT_VTABLE) &&
449+
!(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT) &&
450+
((PM->getRequirements() & OMP_REQ_UNIFIED_SHARED_MEMORY) ||
451+
(PM->getRequirements() & OMPX_REQ_AUTO_ZERO_COPY)))
449452
if (Device.RTL->data_submit(DeviceId, DeviceEntry.Address,
450453
Entry.Address,
451454
Entry.Size) != OFFLOAD_SUCCESS)
452455
REPORT("Failed to write symbol for USM %s\n", Entry.SymbolName);
453-
}
454456
} else if (Entry.Address) {
455457
if (Device.RTL->get_function(Binary, Entry.SymbolName,
456458
&DeviceEntry.Address) != OFFLOAD_SUCCESS)

‎offload/libomptarget/device.cpp‎

Lines changed: 50 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -112,21 +112,58 @@ setupIndirectCallTable(DeviceTy &Device, __tgt_device_image *Image,
112112
llvm::SmallVector<std::pair<void *, void *>> IndirectCallTable;
113113
for (const auto &Entry : Entries) {
114114
if (Entry.Kind != llvm::object::OffloadKind::OFK_OpenMP ||
115-
Entry.Size == 0 || !(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT))
115+
Entry.Size == 0 ||
116+
(!(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT) &&
117+
!(Entry.Flags & OMP_DECLARE_TARGET_INDIRECT_VTABLE)))
116118
continue;
117119

118-
assert(Entry.Size == sizeof(void *) && "Global not a function pointer?");
119-
auto &[HstPtr, DevPtr] = IndirectCallTable.emplace_back();
120-
121-
void *Ptr;
122-
if (Device.RTL->get_global(Binary, Entry.Size, Entry.SymbolName, &Ptr))
123-
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
124-
"failed to load %s", Entry.SymbolName);
125-
126-
HstPtr = Entry.Address;
127-
if (Device.retrieveData(&DevPtr, Ptr, Entry.Size, AsyncInfo))
128-
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
129-
"failed to load %s", Entry.SymbolName);
120+
size_t PtrSize = sizeof(void *);
121+
if (Entry.Flags & OMP_DECLARE_TARGET_INDIRECT_VTABLE) {
122+
// This is a VTable entry, the current entry is the first index of the
123+
// VTable and Entry.Size is the total size of the VTable. Unlike the
124+
// indirect function case below, the Global is not of size Entry.Size and
125+
// is instead of size PtrSize (sizeof(void*)).
126+
void *Vtable;
127+
void *res;
128+
if (Device.RTL->get_global(Binary, PtrSize, Entry.SymbolName, &Vtable))
129+
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
130+
"failed to load %s", Entry.SymbolName);
131+
132+
// HstPtr = Entry.Address;
133+
if (Device.retrieveData(&res, Vtable, PtrSize, AsyncInfo))
134+
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
135+
"failed to load %s", Entry.SymbolName);
136+
if (Device.synchronize(AsyncInfo))
137+
return error::createOffloadError(
138+
error::ErrorCode::INVALID_BINARY,
139+
"failed to synchronize after retrieving %s", Entry.SymbolName);
140+
// Calculate and emplace entire Vtable from first Vtable byte
141+
for (uint64_t i = 0; i < Entry.Size / PtrSize; ++i) {
142+
auto &[HstPtr, DevPtr] = IndirectCallTable.emplace_back();
143+
HstPtr = reinterpret_cast<void *>(
144+
reinterpret_cast<uintptr_t>(Entry.Address) + i * PtrSize);
145+
DevPtr = reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(res) +
146+
i * PtrSize);
147+
}
148+
} else {
149+
// Indirect function case: Entry.Size should equal PtrSize since we're
150+
// dealing with a single function pointer (not a VTable)
151+
assert(Entry.Size == PtrSize && "Global not a function pointer?");
152+
auto &[HstPtr, DevPtr] = IndirectCallTable.emplace_back();
153+
void *Ptr;
154+
if (Device.RTL->get_global(Binary, Entry.Size, Entry.SymbolName, &Ptr))
155+
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
156+
"failed to load %s", Entry.SymbolName);
157+
158+
HstPtr = Entry.Address;
159+
if (Device.retrieveData(&DevPtr, Ptr, Entry.Size, AsyncInfo))
160+
return error::createOffloadError(error::ErrorCode::INVALID_BINARY,
161+
"failed to load %s", Entry.SymbolName);
162+
}
163+
if (Device.synchronize(AsyncInfo))
164+
return error::createOffloadError(
165+
error::ErrorCode::INVALID_BINARY,
166+
"failed to synchronize after retrieving %s", Entry.SymbolName);
130167
}
131168

132169
// If we do not have any indirect globals we exit early.

‎offload/test/api/omp_indirect_call_table_manual.c‎

Lines changed: 107 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,107 @@
1+
// RUN: %libomptarget-compile-run-and-check-generic
2+
#include <assert.h>
3+
#include <omp.h>
4+
#include <stdio.h>
5+
6+
// ---------------------------------------------------------------------------
7+
// Various definitions copied from OpenMP RTL
8+
9+
typedef struct {
10+
uint64_t Reserved;
11+
uint16_t Version;
12+
uint16_t Kind; // OpenMP==1
13+
uint32_t Flags;
14+
void *Address;
15+
char *SymbolName;
16+
uint64_t Size;
17+
uint64_t Data;
18+
void *AuxAddr;
19+
} __tgt_offload_entry;
20+
21+
enum OpenMPOffloadingDeclareTargetFlags {
22+
/// Mark the entry global as having a 'link' attribute.
23+
OMP_DECLARE_TARGET_LINK = 0x01,
24+
/// Mark the entry global as being an indirectly callable function.
25+
OMP_DECLARE_TARGET_INDIRECT = 0x08,
26+
/// This is an entry corresponding to a requirement to be registered.
27+
OMP_REGISTER_REQUIRES = 0x10,
28+
/// Mark the entry global as being an indirect vtable.
29+
OMP_DECLARE_TARGET_INDIRECT_VTABLE = 0x20,
30+
};
31+
32+
#pragma omp begin declare variant match(device = {kind(gpu)})
33+
// Provided by the runtime.
34+
void *__llvm_omp_indirect_call_lookup(void *host_ptr);
35+
#pragma omp declare target to(__llvm_omp_indirect_call_lookup) \
36+
device_type(nohost)
37+
#pragma omp end declare variant
38+
39+
#pragma omp begin declare variant match(device = {kind(cpu)})
40+
// We assume unified addressing on the CPU target.
41+
void *__llvm_omp_indirect_call_lookup(void *host_ptr) { return host_ptr; }
42+
#pragma omp end declare variant
43+
44+
#pragma omp begin declare target
45+
void foo(int *i) { *i += 1; }
46+
void bar(int *i) { *i += 10; }
47+
void baz(int *i) { *i += 100; }
48+
#pragma omp end declare target
49+
50+
typedef void (*fptr_t)(int *i);
51+
52+
// Dispatch Table - declare separately on host and device to avoid
53+
// registering with the library; this also allows us to use separate
54+
// names, which is convenient for debugging. This dispatchTable is
55+
// intended to mimic what Clang emits for C++ vtables.
56+
fptr_t dispatchTable[] = {foo, bar, baz};
57+
#pragma omp begin declare target device_type(nohost)
58+
fptr_t GPUdispatchTable[] = {foo, bar, baz};
59+
fptr_t *GPUdispatchTablePtr = GPUdispatchTable;
60+
#pragma omp end declare target
61+
62+
// Define "manual" OpenMP offload entries, where we emit Clang
63+
// offloading entry structure definitions in the appropriate ELF
64+
// section. This allows us to emulate the offloading entries that Clang would
65+
// normally emit for us
66+
67+
__attribute__((weak, section("llvm_offload_entries"), aligned(8)))
68+
const __tgt_offload_entry __offloading_entry[] = {{
69+
0ULL, // Reserved
70+
1, // Version
71+
1, // Kind
72+
OMP_DECLARE_TARGET_INDIRECT_VTABLE, // Flags
73+
&dispatchTable, // Address
74+
"GPUdispatchTablePtr", // SymbolName
75+
(size_t)(sizeof(dispatchTable)), // Size
76+
0ULL, // Data
77+
NULL // AuxAddr
78+
}};
79+
80+
// Mimic how Clang emits vtable pointers for C++ classes
81+
typedef struct {
82+
fptr_t *dispatchPtr;
83+
} myClass;
84+
85+
// ---------------------------------------------------------------------------
86+
int main() {
87+
myClass obj_foo = {dispatchTable + 0};
88+
myClass obj_bar = {dispatchTable + 1};
89+
myClass obj_baz = {dispatchTable + 2};
90+
int aaa = 0;
91+
92+
#pragma omp target map(aaa) map(to : obj_foo, obj_bar, obj_baz)
93+
{
94+
// Lookup
95+
fptr_t *foo_ptr = __llvm_omp_indirect_call_lookup(obj_foo.dispatchPtr);
96+
fptr_t *bar_ptr = __llvm_omp_indirect_call_lookup(obj_bar.dispatchPtr);
97+
fptr_t *baz_ptr = __llvm_omp_indirect_call_lookup(obj_baz.dispatchPtr);
98+
foo_ptr[0](&aaa);
99+
bar_ptr[0](&aaa);
100+
baz_ptr[0](&aaa);
101+
}
102+
103+
assert(aaa == 111);
104+
// CHECK: PASS
105+
printf("PASS\n");
106+
return 0;
107+
}

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