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//===------ LoopGeneratorsGOMP.cpp - IR helper to create loops ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains functions to create parallel loops as LLVM-IR.
//
//===----------------------------------------------------------------------===//
#include "polly/CodeGen/LoopGeneratorsGOMP.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Module.h"
using namespace llvm;
using namespace polly;
void ParallelLoopGeneratorGOMP::createCallSpawnThreads(Value *SubFn,
Value *SubFnParam,
Value *LB, Value *UB,
Value *Stride) {
const std::string Name = "GOMP_parallel_loop_runtime_start";
Function *F = M->getFunction(Name);
// If F is not available, declare it.
if (!F) {
GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;
Type *Params[] = {PointerType::getUnqual(FunctionType::get(
Builder.getVoidTy(), Builder.getInt8PtrTy(), false)),
Builder.getInt8PtrTy(),
Builder.getInt32Ty(),
LongType,
LongType,
LongType};
FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), Params, false);
F = Function::Create(Ty, Linkage, Name, M);
}
Value *Args[] = {SubFn, SubFnParam, Builder.getInt32(PollyNumThreads),
LB, UB, Stride};
CallInst *Call = Builder.CreateCall(F, Args);
Call->setDebugLoc(DLGenerated);
}
void ParallelLoopGeneratorGOMP::deployParallelExecution(Function *SubFn,
Value *SubFnParam,
Value *LB, Value *UB,
Value *Stride) {
// Tell the runtime we start a parallel loop
createCallSpawnThreads(SubFn, SubFnParam, LB, UB, Stride);
CallInst *Call = Builder.CreateCall(SubFn, SubFnParam);
Call->setDebugLoc(DLGenerated);
createCallJoinThreads();
}
Function *ParallelLoopGeneratorGOMP::prepareSubFnDefinition(Function *F) const {
FunctionType *FT =
FunctionType::get(Builder.getVoidTy(), {Builder.getInt8PtrTy()}, false);
Function *SubFn = Function::Create(FT, Function::InternalLinkage,
F->getName() + "_polly_subfn", M);
// Name the function's arguments
SubFn->arg_begin()->setName("polly.par.userContext");
return SubFn;
}
// Create a subfunction of the following (preliminary) structure:
//
// PrevBB
// |
// v
// HeaderBB
// | _____
// v v |
// CheckNextBB PreHeaderBB
// |\ |
// | \______/
// |
// v
// ExitBB
//
// HeaderBB will hold allocations and loading of variables.
// CheckNextBB will check for more work.
// If there is more work to do: go to PreHeaderBB, otherwise go to ExitBB.
// PreHeaderBB loads the new boundaries (& will lead to the loop body later on).
// ExitBB marks the end of the parallel execution.
std::tuple<Value *, Function *>
ParallelLoopGeneratorGOMP::createSubFn(Value *Stride, AllocaInst *StructData,
SetVector<Value *> Data,
ValueMapT &Map) {
if (PollyScheduling != OMPGeneralSchedulingType::Runtime) {
// User tried to influence the scheduling type (currently not supported)
errs() << "warning: Polly's GNU OpenMP backend solely "
"supports the scheduling type 'runtime'.\n";
}
if (PollyChunkSize != 0) {
// User tried to influence the chunk size (currently not supported)
errs() << "warning: Polly's GNU OpenMP backend solely "
"supports the default chunk size.\n";
}
Function *SubFn = createSubFnDefinition();
LLVMContext &Context = SubFn->getContext();
// Store the previous basic block.
BasicBlock *PrevBB = Builder.GetInsertBlock();
// Create basic blocks.
BasicBlock *HeaderBB = BasicBlock::Create(Context, "polly.par.setup", SubFn);
BasicBlock *ExitBB = BasicBlock::Create(Context, "polly.par.exit", SubFn);
BasicBlock *CheckNextBB =
BasicBlock::Create(Context, "polly.par.checkNext", SubFn);
BasicBlock *PreHeaderBB =
BasicBlock::Create(Context, "polly.par.loadIVBounds", SubFn);
DT.addNewBlock(HeaderBB, PrevBB);
DT.addNewBlock(ExitBB, HeaderBB);
DT.addNewBlock(CheckNextBB, HeaderBB);
DT.addNewBlock(PreHeaderBB, HeaderBB);
// Fill up basic block HeaderBB.
Builder.SetInsertPoint(HeaderBB);
Value *LBPtr = Builder.CreateAlloca(LongType, nullptr, "polly.par.LBPtr");
Value *UBPtr = Builder.CreateAlloca(LongType, nullptr, "polly.par.UBPtr");
Value *UserContext = &*SubFn->arg_begin();
extractValuesFromStruct(Data, StructData->getAllocatedType(), UserContext,
Map);
Builder.CreateBr(CheckNextBB);
// Add code to check if another set of iterations will be executed.
Builder.SetInsertPoint(CheckNextBB);
Value *Next = createCallGetWorkItem(LBPtr, UBPtr);
Value *HasNextSchedule = Builder.CreateTrunc(
Next, Builder.getInt1Ty(), "polly.par.hasNextScheduleBlock");
Builder.CreateCondBr(HasNextSchedule, PreHeaderBB, ExitBB);
// Add code to load the iv bounds for this set of iterations.
Builder.SetInsertPoint(PreHeaderBB);
Value *LB = Builder.CreateLoad(LongType, LBPtr, "polly.par.LB");
Value *UB = Builder.CreateLoad(LongType, UBPtr, "polly.par.UB");
// Subtract one as the upper bound provided by OpenMP is a < comparison
// whereas the codegenForSequential function creates a <= comparison.
UB = Builder.CreateSub(UB, ConstantInt::get(LongType, 1),
"polly.par.UBAdjusted");
Builder.CreateBr(CheckNextBB);
Builder.SetInsertPoint(&*--Builder.GetInsertPoint());
BasicBlock *AfterBB;
Value *IV =
createLoop(LB, UB, Stride, Builder, LI, DT, AfterBB, ICmpInst::ICMP_SLE,
nullptr, true, /* UseGuard */ false);
BasicBlock::iterator LoopBody = Builder.GetInsertPoint();
// Add code to terminate this subfunction.
Builder.SetInsertPoint(ExitBB);
createCallCleanupThread();
Builder.CreateRetVoid();
Builder.SetInsertPoint(&*LoopBody);
return std::make_tuple(IV, SubFn);
}
Value *ParallelLoopGeneratorGOMP::createCallGetWorkItem(Value *LBPtr,
Value *UBPtr) {
const std::string Name = "GOMP_loop_runtime_next";
Function *F = M->getFunction(Name);
// If F is not available, declare it.
if (!F) {
GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;
Type *Params[] = {LongType->getPointerTo(), LongType->getPointerTo()};
FunctionType *Ty = FunctionType::get(Builder.getInt8Ty(), Params, false);
F = Function::Create(Ty, Linkage, Name, M);
}
Value *Args[] = {LBPtr, UBPtr};
CallInst *Call = Builder.CreateCall(F, Args);
Call->setDebugLoc(DLGenerated);
Value *Return = Builder.CreateICmpNE(
Call, Builder.CreateZExt(Builder.getFalse(), Call->getType()));
return Return;
}
void ParallelLoopGeneratorGOMP::createCallJoinThreads() {
const std::string Name = "GOMP_parallel_end";
Function *F = M->getFunction(Name);
// If F is not available, declare it.
if (!F) {
GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;
FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), false);
F = Function::Create(Ty, Linkage, Name, M);
}
CallInst *Call = Builder.CreateCall(F, {});
Call->setDebugLoc(DLGenerated);
}
void ParallelLoopGeneratorGOMP::createCallCleanupThread() {
const std::string Name = "GOMP_loop_end_nowait";
Function *F = M->getFunction(Name);
// If F is not available, declare it.
if (!F) {
GlobalValue::LinkageTypes Linkage = Function::ExternalLinkage;
FunctionType *Ty = FunctionType::get(Builder.getVoidTy(), false);
F = Function::Create(Ty, Linkage, Name, M);
}
CallInst *Call = Builder.CreateCall(F, {});
Call->setDebugLoc(DLGenerated);
}
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