LLVM  12.0.0git
Speculation.cpp
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1 //===---------- speculation.cpp - Utilities for Speculation ----------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
10 #include "llvm/IR/BasicBlock.h"
11 #include "llvm/IR/Function.h"
12 #include "llvm/IR/IRBuilder.h"
13 #include "llvm/IR/Instruction.h"
14 #include "llvm/IR/Instructions.h"
15 #include "llvm/IR/LLVMContext.h"
16 #include "llvm/IR/Module.h"
17 #include "llvm/IR/Type.h"
18 #include "llvm/IR/Verifier.h"
19 
20 namespace llvm {
21 
22 namespace orc {
23 
24 // ImplSymbolMap methods
26  assert(SrcJD && "Tracking on Null Source .impl dylib");
27  std::lock_guard<std::mutex> Lockit(ConcurrentAccess);
28  for (auto &I : ImplMaps) {
29  auto It = Maps.insert({I.first, {I.second.Aliasee, SrcJD}});
30  // check rationale when independent dylibs have same symbol name?
31  assert(It.second && "ImplSymbols are already tracked for this Symbol?");
32  (void)(It);
33  }
34 }
35 
36 // Trigger Speculative Compiles.
37 void Speculator::speculateForEntryPoint(Speculator *Ptr, uint64_t StubId) {
38  assert(Ptr && " Null Address Received in orc_speculate_for ");
39  Ptr->speculateFor(StubId);
40 }
41 
43  MangleAndInterner &Mangle) {
46  JITEvaluatedSymbol SpeculateForEntryPtr(
47  pointerToJITTargetAddress(&speculateForEntryPoint),
49  return JD.define(absoluteSymbols({
50  {Mangle("__orc_speculator"), ThisPtr}, // Data Symbol
51  {Mangle("__orc_speculate_for"), SpeculateForEntryPtr} // Callable Symbol
52  }));
53 }
54 
55 // If two modules, share the same LLVMContext, different threads must
56 // not access them concurrently without locking the associated LLVMContext
57 // this implementation follows this contract.
58 void IRSpeculationLayer::emit(std::unique_ptr<MaterializationResponsibility> R,
59  ThreadSafeModule TSM) {
60 
61  assert(TSM && "Speculation Layer received Null Module ?");
62  assert(TSM.getContext().getContext() != nullptr &&
63  "Module with null LLVMContext?");
64 
65  // Instrumentation of runtime calls, lock the Module
66  TSM.withModuleDo([this, &R](Module &M) {
67  auto &MContext = M.getContext();
68  auto SpeculatorVTy = StructType::create(MContext, "Class.Speculator");
69  auto RuntimeCallTy = FunctionType::get(
70  Type::getVoidTy(MContext),
71  {SpeculatorVTy->getPointerTo(), Type::getInt64Ty(MContext)}, false);
72  auto RuntimeCall =
73  Function::Create(RuntimeCallTy, Function::LinkageTypes::ExternalLinkage,
74  "__orc_speculate_for", &M);
75  auto SpeclAddr = new GlobalVariable(
76  M, SpeculatorVTy, false, GlobalValue::LinkageTypes::ExternalLinkage,
77  nullptr, "__orc_speculator");
78 
79  IRBuilder<> Mutator(MContext);
80 
81  // QueryAnalysis allowed to transform the IR source, one such example is
82  // Simplify CFG helps the static branch prediction heuristics!
83  for (auto &Fn : M.getFunctionList()) {
84  if (!Fn.isDeclaration()) {
85 
86  auto IRNames = QueryAnalysis(Fn);
87  // Instrument and register if Query has result
88  if (IRNames.hasValue()) {
89 
90  // Emit globals for each function.
91  auto LoadValueTy = Type::getInt8Ty(MContext);
92  auto SpeculatorGuard = new GlobalVariable(
93  M, LoadValueTy, false, GlobalValue::LinkageTypes::InternalLinkage,
94  ConstantInt::get(LoadValueTy, 0),
95  "__orc_speculate.guard.for." + Fn.getName());
96  SpeculatorGuard->setAlignment(Align(1));
97  SpeculatorGuard->setUnnamedAddr(GlobalValue::UnnamedAddr::Local);
98 
99  BasicBlock &ProgramEntry = Fn.getEntryBlock();
100  // Create BasicBlocks before the program's entry basicblock
101  BasicBlock *SpeculateBlock = BasicBlock::Create(
102  MContext, "__orc_speculate.block", &Fn, &ProgramEntry);
103  BasicBlock *SpeculateDecisionBlock = BasicBlock::Create(
104  MContext, "__orc_speculate.decision.block", &Fn, SpeculateBlock);
105 
106  assert(SpeculateDecisionBlock == &Fn.getEntryBlock() &&
107  "SpeculateDecisionBlock not updated?");
108  Mutator.SetInsertPoint(SpeculateDecisionBlock);
109 
110  auto LoadGuard =
111  Mutator.CreateLoad(LoadValueTy, SpeculatorGuard, "guard.value");
112  // if just loaded value equal to 0,return true.
113  auto CanSpeculate =
114  Mutator.CreateICmpEQ(LoadGuard, ConstantInt::get(LoadValueTy, 0),
115  "compare.to.speculate");
116  Mutator.CreateCondBr(CanSpeculate, SpeculateBlock, &ProgramEntry);
117 
118  Mutator.SetInsertPoint(SpeculateBlock);
119  auto ImplAddrToUint =
120  Mutator.CreatePtrToInt(&Fn, Type::getInt64Ty(MContext));
121  Mutator.CreateCall(RuntimeCallTy, RuntimeCall,
122  {SpeclAddr, ImplAddrToUint});
123  Mutator.CreateStore(ConstantInt::get(LoadValueTy, 1),
124  SpeculatorGuard);
125  Mutator.CreateBr(&ProgramEntry);
126 
127  assert(Mutator.GetInsertBlock()->getParent() == &Fn &&
128  "IR builder association mismatch?");
129  S.registerSymbols(internToJITSymbols(IRNames.getValue()),
130  &R->getTargetJITDylib());
131  }
132  }
133  }
134  });
135 
136  assert(!TSM.withModuleDo([](const Module &M) { return verifyModule(M); }) &&
137  "Speculation Instrumentation breaks IR?");
138 
139  NextLayer.emit(std::move(R), std::move(TSM));
140 }
141 
142 } // namespace orc
143 } // namespace llvm
This class represents lattice values for constants.
Definition: AllocatorList.h:23
CallInst * CreateCall(FunctionType *FTy, Value *Callee, ArrayRef< Value * > Args=None, const Twine &Name="", MDNode *FPMathTag=nullptr)
Definition: IRBuilder.h:2427
Value * CreateICmpEQ(Value *LHS, Value *RHS, const Twine &Name="")
Definition: IRBuilder.h:2263
A Module instance is used to store all the information related to an LLVM module.
Definition: Module.h:67
Error addSpeculationRuntime(JITDylib &JD, MangleAndInterner &Mangle)
Define symbols for this Speculator object (__orc_speculator) and the speculation runtime entry point ...
Definition: Speculation.cpp:42
static IntegerType * getInt64Ty(LLVMContext &C)
Definition: Type.cpp:198
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:207
StoreInst * CreateStore(Value *Val, Value *Ptr, bool isVolatile=false)
Definition: IRBuilder.h:1730
PointerType * getPointerTo(unsigned AddrSpace=0) const
Return a pointer to the current type.
Definition: Type.cpp:691
BranchInst * CreateCondBr(Value *Cond, BasicBlock *True, BasicBlock *False, MDNode *BranchWeights=nullptr, MDNode *Unpredictable=nullptr)
Create a conditional 'br Cond, TrueDest, FalseDest' instruction.
Definition: IRBuilder.h:1048
Mangles symbol names then uniques them in the context of an ExecutionSession.
Definition: Mangling.h:26
Error define(std::unique_ptr< MaterializationUnitType > &&MU, ResourceTrackerSP RT=nullptr)
Define all symbols provided by the materialization unit to be part of this JITDylib.
Definition: Core.h:1531
BasicBlock * GetInsertBlock() const
Definition: IRBuilder.h:178
static FunctionType * get(Type *Result, ArrayRef< Type * > Params, bool isVarArg)
This static method is the primary way of constructing a FunctionType.
Definition: Type.cpp:321
void speculateFor(TargetFAddr StubAddr)
Definition: Speculation.h:137
BranchInst * CreateBr(BasicBlock *Dest)
Create an unconditional 'br label X' instruction.
Definition: IRBuilder.h:1042
void trackImpls(SymbolAliasMap ImplMaps, JITDylib *SrcJD)
Definition: Speculation.cpp:25
void SetInsertPoint(BasicBlock *TheBB)
This specifies that created instructions should be appended to the end of the specified block.
Definition: IRBuilder.h:184
void emit(std::unique_ptr< MaterializationResponsibility > R, ThreadSafeModule TSM) override
Emit should materialize the given IR.
Definition: Speculation.cpp:58
static Function * Create(FunctionType *Ty, LinkageTypes Linkage, unsigned AddrSpace, const Twine &N="", Module *M=nullptr)
Definition: Function.h:137
LLVM Basic Block Representation.
Definition: BasicBlock.h:58
LLVMContext * getContext()
Returns a pointer to the LLVMContext that was used to construct this instance, or null if the instanc...
JITTargetAddress pointerToJITTargetAddress(T *Ptr)
Convert a pointer to a JITTargetAddress.
Definition: JITSymbol.h:69
ThreadSafeContext getContext() const
Returns the context for this ThreadSafeModule.
void registerSymbols(FunctionCandidatesMap Candidates, JITDylib *JD)
Definition: Speculation.h:140
static Type * getVoidTy(LLVMContext &C)
Definition: Type.cpp:180
void emit(std::unique_ptr< MaterializationResponsibility > R, ThreadSafeModule TSM) override
Emit should materialize the given IR.
static BasicBlock * Create(LLVMContext &Context, const Twine &Name="", Function *Parent=nullptr, BasicBlock *InsertBefore=nullptr)
Creates a new BasicBlock.
Definition: BasicBlock.h:100
An LLVM Module together with a shared ThreadSafeContext.
uint64_t Align
decltype(auto) withModuleDo(Func &&F)
Locks the associated ThreadSafeContext and calls the given function on the contained Module.
LoadInst * CreateLoad(Type *Ty, Value *Ptr, const char *Name)
Provided to resolve 'CreateLoad(Ty, Ptr, "...")' correctly, instead of converting the string to 'bool...
Definition: IRBuilder.h:1701
std::unique_ptr< AbsoluteSymbolsMaterializationUnit > absoluteSymbols(SymbolMap Symbols)
Create an AbsoluteSymbolsMaterializationUnit with the given symbols.
Definition: Core.h:716
Module.h This file contains the declarations for the Module class.
static Constant * get(Type *Ty, uint64_t V, bool isSigned=false)
If Ty is a vector type, return a Constant with a splat of the given value.
Definition: Constants.cpp:867
Represents a symbol that has been evaluated to an address already.
Definition: JITSymbol.h:229
void setAlignment(MaybeAlign Align)
Definition: Globals.cpp:117
StringRef getName() const
Return a constant reference to the value's name.
Definition: Value.cpp:295
const Function * getParent() const
Return the enclosing method, or null if none.
Definition: BasicBlock.h:107
#define I(x, y, z)
Definition: MD5.cpp:59
Value * CreatePtrToInt(Value *V, Type *DestTy, const Twine &Name="")
Definition: IRBuilder.h:2139
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static StructType * create(LLVMContext &Context, StringRef Name)
This creates an identified struct.
Definition: Type.cpp:461
Lightweight error class with error context and mandatory checking.
Definition: Error.h:157
OutputIt move(R &&Range, OutputIt Out)
Provide wrappers to std::move which take ranges instead of having to pass begin/end explicitly.
Definition: STLExtras.h:1556
static IntegerType * getInt8Ty(LLVMContext &C)
Definition: Type.cpp:195
A symbol table that supports asynchoronous symbol queries.
Definition: Core.h:894