1 /* Copyright 2017 The TensorFlow Authors. All Rights Reserved.
2
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9 Unless required by applicable law or agreed to in writing, software
10 distributed under the License is distributed on an "AS IS" BASIS,
11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 See the License for the specific language governing permissions and
13 limitations under the License.
14 ==============================================================================*/
15
16 #include "tensorflow/compiler/xla/service/llvm_ir/kernel_support_library.h"
17
18 #include "tensorflow/compiler/xla/service/llvm_ir/llvm_util.h"
19
20 namespace xla {
ForWithStatus(absl::string_view name,llvm::Value * start,llvm::Value * end,llvm::Value * step,const std::function<Status (llvm::Value *,bool)> & for_body_generator)21 Status KernelSupportLibrary::ForWithStatus(
22 absl::string_view name, llvm::Value* start, llvm::Value* end,
23 llvm::Value* step,
24 const std::function<Status(llvm::Value*, bool)>& for_body_generator) {
25 return IfWithStatus(b_->CreateICmpSLT(start, end), [&]() -> Status {
26 TF_RETURN_IF_ERROR(for_body_generator(start, /*is_first_iteration=*/true));
27 return ForWithStatus(
28 name, b_->CreateAdd(start, step), end, step,
29 [&](llvm::Value* iv) { return for_body_generator(iv, false); });
30 });
31 }
32
ForWithStatus(absl::string_view name,llvm::Value * start,llvm::Value * end,llvm::Value * step,bool peel_first_iteration,const std::function<Status (llvm::Value *,llvm::Value *)> & for_body_generator)33 Status KernelSupportLibrary::ForWithStatus(
34 absl::string_view name, llvm::Value* start, llvm::Value* end,
35 llvm::Value* step, bool peel_first_iteration,
36 const std::function<Status(llvm::Value*, llvm::Value*)>&
37 for_body_generator) {
38 if (peel_first_iteration) {
39 return ForWithStatus(
40 name, start, end, step, true,
41 [&](llvm::Value* indvar, bool is_first_iteration) -> Status {
42 return for_body_generator(indvar, b_->getInt1(is_first_iteration));
43 });
44 } else {
45 std::unique_ptr<llvm_ir::ForLoop> loop = llvm_ir::ForLoop::EmitForLoop(
46 name, start, end, step, b_,
47 /*unroll_mode=*/unroll_mode_,
48 /*prevent_vectorization=*/prevent_vectorization_);
49 b_->SetInsertPoint(&loop->GetBodyBasicBlock()->back());
50 TF_RETURN_IF_ERROR(
51 for_body_generator(loop->GetIndVarValue(),
52 /*is_first_iteration=*/b_->CreateICmpEQ(
53 loop->GetIndVarValue(), start)));
54 llvm_ir::SetToLastInsertPoint(loop->GetExitBasicBlock(), b_);
55 return Status::OK();
56 }
57 }
58
IfWithStatus(absl::string_view name,llvm::Value * condition,const std::function<Status ()> & true_block_generator,const std::function<Status ()> & false_block_generator)59 Status KernelSupportLibrary::IfWithStatus(
60 absl::string_view name, llvm::Value* condition,
61 const std::function<Status()>& true_block_generator,
62 const std::function<Status()>& false_block_generator) {
63 llvm_ir::LlvmIfData if_data = llvm_ir::EmitIfThenElse(condition, name, b_);
64 b_->SetInsertPoint(&if_data.true_block->back());
65 TF_RETURN_IF_ERROR(true_block_generator());
66 b_->SetInsertPoint(&if_data.false_block->back());
67 TF_RETURN_IF_ERROR(false_block_generator());
68 llvm_ir::SetToLastInsertPoint(if_data.after_block, b_);
69 return Status::OK();
70 }
71
EmitAndCallOutlinedKernel(const HloModuleConfig & module_config,llvm::IRBuilder<> * b,absl::string_view kernel_name,KernelSupportLibrary::ArgumentVector arguments,const std::function<void (KernelSupportLibrary::ArgumentVector)> & kernel_body_generator)72 void KernelSupportLibrary::EmitAndCallOutlinedKernel(
73 const HloModuleConfig& module_config, llvm::IRBuilder<>* b,
74 absl::string_view kernel_name,
75 KernelSupportLibrary::ArgumentVector arguments,
76 const std::function<void(KernelSupportLibrary::ArgumentVector)>&
77 kernel_body_generator) {
78 llvm::Module* module = b->GetInsertBlock()->getModule();
79 llvm::Function* function =
80 module->getFunction(llvm_ir::AsStringRef(kernel_name));
81
82 int64 null_arg_idx = -1;
83 std::vector<llvm::Value*> sanitized_args;
84 sanitized_args.reserve(arguments.size());
85 for (int64 i = 0, e = arguments.size(); i < e; i++) {
86 if (arguments[i]) {
87 sanitized_args.push_back(arguments[i]);
88 } else {
89 CHECK_EQ(null_arg_idx, -1);
90 null_arg_idx = i;
91 }
92 }
93
94 if (!function) {
95 VLOG(2) << "Generating kernel for " << kernel_name;
96 std::vector<llvm::Type*> arg_types;
97 std::transform(sanitized_args.begin(), sanitized_args.end(),
98 std::back_inserter(arg_types),
99 [](llvm::Value* arg) { return arg->getType(); });
100
101 auto* function_type =
102 llvm::FunctionType::get(b->getVoidTy(), arg_types, /*isVarArg=*/false);
103
104 function = llvm_ir::CreateCpuFunction(function_type,
105 llvm::GlobalValue::InternalLinkage,
106 module_config, kernel_name, module);
107
108 llvm::IRBuilder<>::InsertPointGuard guard(*b);
109
110 auto* entry_bb =
111 llvm::BasicBlock::Create(b->getContext(), "entry", function);
112 auto* return_inst = llvm::ReturnInst::Create(b->getContext(),
113 /*retVal=*/nullptr, entry_bb);
114 // Set the insert point to before return_inst.
115 b->SetInsertPoint(return_inst);
116
117 std::vector<llvm::Value*> arg_values;
118 /*
119 * clang on OSX doesn't like std::transform or range for loop here.
120 * See https://github.com/tensorflow/tensorflow/issues/15196
121 */
122 for (llvm::Function::arg_iterator arg = function->arg_begin(),
123 arg_e = function->arg_end();
124 arg != arg_e; ++arg) {
125 arg_values.push_back(arg);
126 }
127 if (null_arg_idx != -1) {
128 arg_values.insert(arg_values.begin() + null_arg_idx, nullptr);
129 }
130 kernel_body_generator(arg_values);
131 } else {
132 VLOG(3) << "Re-using kernel for " << kernel_name;
133 }
134
135 b->CreateCall(function, llvm_ir::AsArrayRef(sanitized_args));
136 }
137
138 } // namespace xla
139