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//===------ PerfMonitor.cpp - Generate a run-time performance monitor. -======//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//
#include "polly/CodeGen/PerfMonitor.h"
#include "polly/CodeGen/RuntimeDebugBuilder.h"
#include "llvm/ADT/Triple.h"
#include "llvm/IR/Intrinsics.h"
using namespace llvm;
using namespace polly;
Function *PerfMonitor::getAtExit() {
const char *Name = "atexit";
Function *F = M->getFunction(Name);
if (!F) {
GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;
FunctionType *Ty = FunctionType::get(Builder.getInt32Ty(),
{Builder.getInt8PtrTy()}, false);
F = Function::Create(Ty, Linkage, Name, M);
}
return F;
}
void PerfMonitor::addToGlobalConstructors(Function *Fn) {
const char *Name = "llvm.global_ctors";
GlobalVariable *GV = M->getGlobalVariable(Name);
std::vector<Constant *> V;
if (GV) {
Constant *Array = GV->getInitializer();
for (Value *X : Array->operand_values())
V.push_back(cast<Constant>(X));
GV->eraseFromParent();
}
StructType *ST = StructType::get(Builder.getInt32Ty(), Fn->getType(),
Builder.getInt8PtrTy(), nullptr);
V.push_back(ConstantStruct::get(
ST, Builder.getInt32(10), Fn,
ConstantPointerNull::get(Builder.getInt8PtrTy()), nullptr));
ArrayType *Ty = ArrayType::get(ST, V.size());
GV = new GlobalVariable(*M, Ty, true, GlobalValue::AppendingLinkage,
ConstantArray::get(Ty, V), Name, nullptr,
GlobalVariable::NotThreadLocal);
}
Function *PerfMonitor::getRDTSCP() {
return Intrinsic::getDeclaration(M, Intrinsic::x86_rdtscp);
}
PerfMonitor::PerfMonitor(Module *M) : M(M), Builder(M->getContext()) {
if (Triple(M->getTargetTriple()).getArch() == llvm::Triple::x86_64)
Supported = true;
else
Supported = false;
}
void PerfMonitor::addGlobalVariables() {
auto TryRegisterGlobal = [=](const char *Name, Constant *InitialValue,
Value **Location) {
*Location = M->getGlobalVariable(Name);
if (!*Location)
*Location = new GlobalVariable(
*M, InitialValue->getType(), true, GlobalValue::WeakAnyLinkage,
InitialValue, Name, nullptr, GlobalVariable::InitialExecTLSModel);
};
TryRegisterGlobal("__polly_perf_cycles_total_start", Builder.getInt64(0),
&CyclesTotalStartPtr);
TryRegisterGlobal("__polly_perf_initialized", Builder.getInt1(0),
&AlreadyInitializedPtr);
TryRegisterGlobal("__polly_perf_cycles_in_scops", Builder.getInt64(0),
&CyclesInScopsPtr);
TryRegisterGlobal("__polly_perf_cycles_in_scop_start", Builder.getInt64(0),
&CyclesInScopStartPtr);
TryRegisterGlobal("__polly_perf_write_loation", Builder.getInt32(0),
&RDTSCPWriteLocation);
}
static const char *InitFunctionName = "__polly_perf_init";
static const char *FinalReportingFunctionName = "__polly_perf_final";
Function *PerfMonitor::insertFinalReporting() {
// Create new function.
GlobalValue::LinkageTypes Linkage = Function::WeakODRLinkage;
FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), {}, false);
Function *ExitFn =
Function::Create(Ty, Linkage, FinalReportingFunctionName, M);
BasicBlock *Start = BasicBlock::Create(M->getContext(), "start", ExitFn);
Builder.SetInsertPoint(Start);
if (!Supported) {
RuntimeDebugBuilder::createCPUPrinter(
Builder, "Polly runtime information generation not supported\n");
Builder.CreateRetVoid();
return ExitFn;
}
// Measure current cycles and compute final timings.
Function *RDTSCPFn = getRDTSCP();
Value *CurrentCycles = Builder.CreateCall(
RDTSCPFn,
Builder.CreatePointerCast(RDTSCPWriteLocation, Builder.getInt8PtrTy()));
Value *CyclesStart = Builder.CreateLoad(CyclesTotalStartPtr, true);
Value *CyclesTotal = Builder.CreateSub(CurrentCycles, CyclesStart);
Value *CyclesInScops = Builder.CreateLoad(CyclesInScopsPtr, true);
// Print the runtime information.
RuntimeDebugBuilder::createCPUPrinter(Builder, "Polly runtime information\n");
RuntimeDebugBuilder::createCPUPrinter(Builder, "-------------------------\n");
RuntimeDebugBuilder::createCPUPrinter(Builder, "Total: ", CyclesTotal, "\n");
RuntimeDebugBuilder::createCPUPrinter(Builder, "Scops: ", CyclesInScops,
"\n");
// Finalize function.
Builder.CreateRetVoid();
return ExitFn;
}
void PerfMonitor::initialize() {
addGlobalVariables();
Function *F = M->getFunction(InitFunctionName);
if (F)
return;
// initialize
Function *FinalReporting = insertFinalReporting();
Function *InitFn = insertInitFunction(FinalReporting);
addToGlobalConstructors(InitFn);
}
Function *PerfMonitor::insertInitFunction(Function *FinalReporting) {
// Insert function definition and BBs.
GlobalValue::LinkageTypes Linkage = Function::WeakODRLinkage;
FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), {}, false);
Function *InitFn = Function::Create(Ty, Linkage, InitFunctionName, M);
BasicBlock *Start = BasicBlock::Create(M->getContext(), "start", InitFn);
BasicBlock *EarlyReturn =
BasicBlock::Create(M->getContext(), "earlyreturn", InitFn);
BasicBlock *InitBB = BasicBlock::Create(M->getContext(), "initbb", InitFn);
Builder.SetInsertPoint(Start);
// Check if this function was already run. If yes, return.
//
// In case profiling has been enabled in multiple translation units, the
// initializer function will be added to the global constructors list of
// each translation unit. When merging translation units, the global
// constructor lists are just appended, such that the initializer will appear
// multiple times. To avoid initializations being run multiple times (and
// especially to avoid that atExitFn is called more than once), we bail
// out if the intializer is run more than once.
Value *HasRunBefore = Builder.CreateLoad(AlreadyInitializedPtr);
Builder.CreateCondBr(HasRunBefore, EarlyReturn, InitBB);
Builder.SetInsertPoint(EarlyReturn);
Builder.CreateRetVoid();
// Keep track that this function has been run once.
Builder.SetInsertPoint(InitBB);
Value *True = Builder.getInt1(true);
Builder.CreateStore(True, AlreadyInitializedPtr);
// Register the final reporting function with atexit().
Value *FinalReportingPtr =
Builder.CreatePointerCast(FinalReporting, Builder.getInt8PtrTy());
Function *AtExitFn = getAtExit();
Builder.CreateCall(AtExitFn, {FinalReportingPtr});
if (Supported) {
// Read the currently cycle counter and store the result for later.
Function *RDTSCPFn = getRDTSCP();
Value *CurrentCycles = Builder.CreateCall(
RDTSCPFn,
Builder.CreatePointerCast(RDTSCPWriteLocation, Builder.getInt8PtrTy()));
Builder.CreateStore(CurrentCycles, CyclesTotalStartPtr, true);
}
Builder.CreateRetVoid();
return InitFn;
}
void PerfMonitor::insertRegionStart(Instruction *InsertBefore) {
if (!Supported)
return;
Builder.SetInsertPoint(InsertBefore);
Function *RDTSCPFn = getRDTSCP();
Value *CurrentCycles = Builder.CreateCall(
RDTSCPFn,
Builder.CreatePointerCast(RDTSCPWriteLocation, Builder.getInt8PtrTy()));
Builder.CreateStore(CurrentCycles, CyclesInScopStartPtr, true);
}
void PerfMonitor::insertRegionEnd(Instruction *InsertBefore) {
if (!Supported)
return;
Builder.SetInsertPoint(InsertBefore);
Function *RDTSCPFn = getRDTSCP();
LoadInst *CyclesStart = Builder.CreateLoad(CyclesInScopStartPtr, true);
Value *CurrentCycles = Builder.CreateCall(
RDTSCPFn,
Builder.CreatePointerCast(RDTSCPWriteLocation, Builder.getInt8PtrTy()));
Value *CyclesInScop = Builder.CreateSub(CurrentCycles, CyclesStart);
Value *CyclesInScops = Builder.CreateLoad(CyclesInScopsPtr, true);
CyclesInScops = Builder.CreateAdd(CyclesInScops, CyclesInScop);
Builder.CreateStore(CyclesInScops, CyclesInScopsPtr, true);
}
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