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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 =
64       llvm_ir::EmitIfThenElse(condition, name, b_,
65                               /*emit_else=*/false_block_generator != nullptr);
66   b_->SetInsertPoint(&if_data.true_block->back());
67   TF_RETURN_IF_ERROR(true_block_generator());
68   if (false_block_generator != nullptr) {
69     b_->SetInsertPoint(&if_data.false_block->back());
70     TF_RETURN_IF_ERROR(false_block_generator());
71   }
72   llvm_ir::SetToLastInsertPoint(if_data.after_block, b_);
73   return Status::OK();
74 }
75 
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)76 void KernelSupportLibrary::EmitAndCallOutlinedKernel(
77     const HloModuleConfig& module_config, llvm::IRBuilder<>* b,
78     absl::string_view kernel_name,
79     KernelSupportLibrary::ArgumentVector arguments,
80     const std::function<void(KernelSupportLibrary::ArgumentVector)>&
81         kernel_body_generator) {
82   llvm::Module* module = b->GetInsertBlock()->getModule();
83   llvm::Function* function =
84       module->getFunction(llvm_ir::AsStringRef(kernel_name));
85 
86   int64 null_arg_idx = -1;
87   std::vector<llvm::Value*> sanitized_args;
88   sanitized_args.reserve(arguments.size());
89   for (int64 i = 0, e = arguments.size(); i < e; i++) {
90     if (arguments[i]) {
91       sanitized_args.push_back(arguments[i]);
92     } else {
93       CHECK_EQ(null_arg_idx, -1);
94       null_arg_idx = i;
95     }
96   }
97 
98   if (!function) {
99     VLOG(2) << "Generating kernel for " << kernel_name;
100     std::vector<llvm::Type*> arg_types;
101     std::transform(sanitized_args.begin(), sanitized_args.end(),
102                    std::back_inserter(arg_types),
103                    [](llvm::Value* arg) { return arg->getType(); });
104 
105     auto* function_type =
106         llvm::FunctionType::get(b->getVoidTy(), arg_types, /*isVarArg=*/false);
107 
108     function = llvm_ir::CreateCpuFunction(function_type,
109                                           llvm::GlobalValue::InternalLinkage,
110                                           module_config, kernel_name, module);
111 
112     llvm::IRBuilder<>::InsertPointGuard guard(*b);
113 
114     auto* entry_bb =
115         llvm::BasicBlock::Create(b->getContext(), "entry", function);
116     auto* return_inst = llvm::ReturnInst::Create(b->getContext(),
117                                                  /*retVal=*/nullptr, entry_bb);
118     // Set the insert point to before return_inst.
119     b->SetInsertPoint(return_inst);
120 
121     std::vector<llvm::Value*> arg_values;
122     /*
123      * clang on OSX doesn't like std::transform or range for loop here.
124      * See https://github.com/tensorflow/tensorflow/issues/15196
125      */
126     for (llvm::Function::arg_iterator arg = function->arg_begin(),
127                                       arg_e = function->arg_end();
128          arg != arg_e; ++arg) {
129       arg_values.push_back(arg);
130     }
131     if (null_arg_idx != -1) {
132       arg_values.insert(arg_values.begin() + null_arg_idx, nullptr);
133     }
134     kernel_body_generator(arg_values);
135   } else {
136     VLOG(3) << "Re-using kernel for " << kernel_name;
137   }
138 
139   b->CreateCall(function, llvm_ir::AsArrayRef(sanitized_args));
140 }
141 
142 }  // namespace xla
143