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llvm-project/polly/lib/CodeGen/IslCodeGeneration.cpp

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//===------ IslCodeGeneration.cpp - Code generate the Scops using ISL. ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// The IslCodeGeneration pass takes a Scop created by ScopInfo and translates it
// back to LLVM-IR using the ISL code generator.
//
// The Scop describes the high level memory behaviour of a control flow region.
// Transformation passes can update the schedule (execution order) of statements
// in the Scop. ISL is used to generate an abstract syntax tree that reflects
// the updated execution order. This clast is used to create new LLVM-IR that is
// computationally equivalent to the original control flow region, but executes
// its code in the new execution order defined by the changed scattering.
//
//===----------------------------------------------------------------------===//
#include "polly/Config/config.h"
#include "polly/CodeGen/IslExprBuilder.h"
#include "polly/CodeGen/BlockGenerators.h"
#include "polly/CodeGen/CodeGeneration.h"
#include "polly/CodeGen/IslAst.h"
#include "polly/CodeGen/LoopGenerators.h"
#include "polly/CodeGen/Utils.h"
#include "polly/Dependences.h"
#include "polly/LinkAllPasses.h"
#include "polly/ScopInfo.h"
#include "polly/Support/GICHelper.h"
#include "polly/Support/ScopHelper.h"
#include "polly/Support/SCEVValidator.h"
#include "polly/TempScopInfo.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/PostDominators.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "isl/union_map.h"
#include "isl/list.h"
#include "isl/ast.h"
#include "isl/ast_build.h"
#include "isl/set.h"
#include "isl/map.h"
#include "isl/aff.h"
using namespace polly;
using namespace llvm;
#define DEBUG_TYPE "polly-codegen-isl"
class IslNodeBuilder {
public:
IslNodeBuilder(PollyIRBuilder &Builder, ScopAnnotator &Annotator, Pass *P,
const DataLayout &DL, LoopInfo &LI, ScalarEvolution &SE,
DominatorTree &DT, Scop &S)
: S(S), Builder(Builder), Annotator(Annotator),
Rewriter(new SCEVExpander(SE, "polly")),
ExprBuilder(Builder, IDToValue, *Rewriter),
BlockGen(Builder, LI, SE, DT, &ExprBuilder), P(P), DL(DL), LI(LI),
SE(SE), DT(DT) {}
~IslNodeBuilder() { delete Rewriter; }
void addParameters(__isl_take isl_set *Context);
void create(__isl_take isl_ast_node *Node);
IslExprBuilder &getExprBuilder() { return ExprBuilder; }
private:
Scop &S;
PollyIRBuilder &Builder;
ScopAnnotator &Annotator;
/// @brief A SCEVExpander to create llvm values from SCEVs.
SCEVExpander *Rewriter;
IslExprBuilder ExprBuilder;
BlockGenerator BlockGen;
Pass *P;
const DataLayout &DL;
LoopInfo &LI;
ScalarEvolution &SE;
DominatorTree &DT;
/// @brief The current iteration of out-of-scop loops
///
/// This map provides for a given loop a llvm::Value that contains the current
/// loop iteration.
LoopToScevMapT OutsideLoopIterations;
// This maps an isl_id* to the Value* it has in the generated program. For now
// on, the only isl_ids that are stored here are the newly calculated loop
// ivs.
IslExprBuilder::IDToValueTy IDToValue;
/// Generate code for a given SCEV*
///
/// This function generates code for a given SCEV expression. It generated
/// code is emmitted at the end of the basic block our Builder currently
/// points to and the resulting value is returned.
///
/// @param Expr The expression to code generate.
Value *generateSCEV(const SCEV *Expr);
/// A set of Value -> Value remappings to apply when generating new code.
///
/// When generating new code for a ScopStmt this map is used to map certain
/// llvm::Values to new llvm::Values.
ValueMapT ValueMap;
// Extract the upper bound of this loop
//
// The isl code generation can generate arbitrary expressions to check if the
// upper bound of a loop is reached, but it provides an option to enforce
// 'atomic' upper bounds. An 'atomic upper bound is always of the form
// iv <= expr, where expr is an (arbitrary) expression not containing iv.
//
// This function extracts 'atomic' upper bounds. Polly, in general, requires
// atomic upper bounds for the following reasons:
//
// 1. An atomic upper bound is loop invariant
//
// It must not be calculated at each loop iteration and can often even be
// hoisted out further by the loop invariant code motion.
//
// 2. OpenMP needs a loop invarient upper bound to calculate the number
// of loop iterations.
//
// 3. With the existing code, upper bounds have been easier to implement.
__isl_give isl_ast_expr *getUpperBound(__isl_keep isl_ast_node *For,
CmpInst::Predicate &Predicate);
unsigned getNumberOfIterations(__isl_keep isl_ast_node *For);
/// Compute the values and loops referenced in this subtree.
///
/// This function looks at all ScopStmts scheduled below the provided For node
/// and finds the llvm::Value[s] and llvm::Loops[s] which are referenced but
/// not locally defined.
///
/// Values that can be synthesized or that are available as globals are
/// considered locally defined.
///
/// Loops that contain the scop or that are part of the scop are considered
/// locally defined. Loops that are before the scop, but do not contain the
/// scop itself are considered not locally defined.
///
/// @param For The node defining the subtree.
/// @param Values A vector that will be filled with the Values referenced in
/// this subtree.
/// @param Loops A vector that will be filled with the Loops referenced in
/// this subtree.
void getReferencesInSubtree(__isl_keep isl_ast_node *For,
SetVector<Value *> &Values,
SetVector<const Loop *> &Loops);
/// Change the llvm::Value(s) used for code generation.
///
/// When generating code certain values (e.g., references to induction
/// variables or array base pointers) in the original code may be replaced by
/// new values. This function allows to (partially) update the set of values
/// used. A typical use case for this function is the case when we continue
/// code generation in a subfunction/kernel function and need to explicitly
/// pass down certain values.
///
/// @param NewValues A map that maps certain llvm::Values to new llvm::Values.
void updateValues(ParallelLoopGenerator::ValueToValueMapTy &NewValues);
void createFor(__isl_take isl_ast_node *For);
void createForVector(__isl_take isl_ast_node *For, int VectorWidth);
void createForSequential(__isl_take isl_ast_node *For);
/// Create LLVM-IR that executes a for node thread parallel.
///
/// @param For The FOR isl_ast_node for which code is generated.
void createForParallel(__isl_take isl_ast_node *For);
/// Generate LLVM-IR that computes the values of the original induction
/// variables in function of the newly generated loop induction variables.
///
/// Example:
///
/// // Original
/// for i
/// for j
/// S(i)
///
/// Schedule: [i,j] -> [i+j, j]
///
/// // New
/// for c0
/// for c1
/// S(c0 - c1, c1)
///
/// Assuming the original code consists of two loops which are
/// transformed according to a schedule [i,j] -> [c0=i+j,c1=j]. The resulting
/// ast models the original statement as a call expression where each argument
/// is an expression that computes the old induction variables from the new
/// ones, ordered such that the first argument computes the value of induction
/// variable that was outermost in the original code.
///
/// @param Expr The call expression that represents the statement.
/// @param Stmt The statement that is called.
/// @param VMap The value map into which the mapping from the old induction
/// variable to the new one is inserted. This mapping is used
/// for the classical code generation (not scev-based) and
/// gives an explicit mapping from an original, materialized
/// induction variable. It consequently can only be expressed
/// if there was an explicit induction variable.
/// @param LTS The loop to SCEV map in which the mapping from the original
/// loop to a SCEV representing the new loop iv is added. This
/// mapping does not require an explicit induction variable.
/// Instead, we think in terms of an implicit induction variable
/// that counts the number of times a loop is executed. For each
/// original loop this count, expressed in function of the new
/// induction variables, is added to the LTS map.
void createSubstitutions(__isl_take isl_ast_expr *Expr, ScopStmt *Stmt,
ValueMapT &VMap, LoopToScevMapT &LTS);
void createSubstitutionsVector(__isl_take isl_ast_expr *Expr, ScopStmt *Stmt,
VectorValueMapT &VMap,
std::vector<LoopToScevMapT> &VLTS,
std::vector<Value *> &IVS,
__isl_take isl_id *IteratorID);
void createIf(__isl_take isl_ast_node *If);
void createUserVector(__isl_take isl_ast_node *User,
std::vector<Value *> &IVS,
__isl_take isl_id *IteratorID,
__isl_take isl_union_map *Schedule);
void createUser(__isl_take isl_ast_node *User);
void createBlock(__isl_take isl_ast_node *Block);
};
__isl_give isl_ast_expr *
IslNodeBuilder::getUpperBound(__isl_keep isl_ast_node *For,
ICmpInst::Predicate &Predicate) {
isl_id *UBID, *IteratorID;
isl_ast_expr *Cond, *Iterator, *UB, *Arg0;
isl_ast_op_type Type;
Cond = isl_ast_node_for_get_cond(For);
Iterator = isl_ast_node_for_get_iterator(For);
isl_ast_expr_get_type(Cond);
assert(isl_ast_expr_get_type(Cond) == isl_ast_expr_op &&
"conditional expression is not an atomic upper bound");
Type = isl_ast_expr_get_op_type(Cond);
switch (Type) {
case isl_ast_op_le:
Predicate = ICmpInst::ICMP_SLE;
break;
case isl_ast_op_lt:
Predicate = ICmpInst::ICMP_SLT;
break;
default:
llvm_unreachable("Unexpected comparision type in loop conditon");
}
Arg0 = isl_ast_expr_get_op_arg(Cond, 0);
assert(isl_ast_expr_get_type(Arg0) == isl_ast_expr_id &&
"conditional expression is not an atomic upper bound");
UBID = isl_ast_expr_get_id(Arg0);
assert(isl_ast_expr_get_type(Iterator) == isl_ast_expr_id &&
"Could not get the iterator");
IteratorID = isl_ast_expr_get_id(Iterator);
assert(UBID == IteratorID &&
"conditional expression is not an atomic upper bound");
UB = isl_ast_expr_get_op_arg(Cond, 1);
isl_ast_expr_free(Cond);
isl_ast_expr_free(Iterator);
isl_ast_expr_free(Arg0);
isl_id_free(IteratorID);
isl_id_free(UBID);
return UB;
}
unsigned IslNodeBuilder::getNumberOfIterations(__isl_keep isl_ast_node *For) {
isl_union_map *Schedule = IslAstInfo::getSchedule(For);
isl_set *LoopDomain = isl_set_from_union_set(isl_union_map_range(Schedule));
int NumberOfIterations = polly::getNumberOfIterations(LoopDomain);
if (NumberOfIterations == -1)
return -1;
return NumberOfIterations + 1;
}
struct FindValuesUser {
LoopInfo &LI;
ScalarEvolution &SE;
Region &R;
SetVector<Value *> &Values;
SetVector<const SCEV *> &SCEVs;
};
/// Extract the values and SCEVs needed to generate code for a ScopStmt.
///
/// This function extracts a ScopStmt from a given isl_set and computes the
/// Values this statement depends on as well as a set of SCEV expressions that
/// need to be synthesized when generating code for this statment.
static int findValuesInStmt(isl_set *Set, void *UserPtr) {
isl_id *Id = isl_set_get_tuple_id(Set);
struct FindValuesUser &User = *static_cast<struct FindValuesUser *>(UserPtr);
const ScopStmt *Stmt = static_cast<const ScopStmt *>(isl_id_get_user(Id));
const BasicBlock *BB = Stmt->getBasicBlock();
// Check all the operands of instructions in the basic block.
for (const Instruction &Inst : *BB) {
for (Value *SrcVal : Inst.operands()) {
if (Instruction *OpInst = dyn_cast<Instruction>(SrcVal))
if (canSynthesize(OpInst, &User.LI, &User.SE, &User.R)) {
User.SCEVs.insert(
User.SE.getSCEVAtScope(OpInst, User.LI.getLoopFor(BB)));
continue;
}
if (Instruction *OpInst = dyn_cast<Instruction>(SrcVal))
if (Stmt->getParent()->getRegion().contains(OpInst))
continue;
if (isa<Instruction>(SrcVal) || isa<Argument>(SrcVal))
User.Values.insert(SrcVal);
}
}
isl_id_free(Id);
isl_set_free(Set);
return 0;
}
void IslNodeBuilder::getReferencesInSubtree(__isl_keep isl_ast_node *For,
SetVector<Value *> &Values,
SetVector<const Loop *> &Loops) {
SetVector<const SCEV *> SCEVs;
struct FindValuesUser FindValues = {LI, SE, S.getRegion(), Values, SCEVs};
for (const auto &I : IDToValue)
Values.insert(I.second);
for (const auto &I : OutsideLoopIterations)
Values.insert(cast<SCEVUnknown>(I.second)->getValue());
isl_union_set *Schedule = isl_union_map_domain(IslAstInfo::getSchedule(For));
isl_union_set_foreach_set(Schedule, findValuesInStmt, &FindValues);
isl_union_set_free(Schedule);
for (const SCEV *Expr : SCEVs) {
findValues(Expr, Values);
findLoops(Expr, Loops);
}
Values.remove_if([](const Value *V) { return isa<GlobalValue>(V); });
/// Remove loops that contain the scop or that are part of the scop, as they
/// are considered local. This leaves only loops that are before the scop, but
/// do not contain the scop itself.
Loops.remove_if([this](const Loop *L) {
return this->S.getRegion().contains(L) ||
L->contains(S.getRegion().getEntry());
});
}
void IslNodeBuilder::updateValues(
ParallelLoopGenerator::ValueToValueMapTy &NewValues) {
SmallPtrSet<Value *, 5> Inserted;
for (const auto &I : IDToValue) {
IDToValue[I.first] = NewValues[I.second];
Inserted.insert(I.second);
}
for (const auto &I : NewValues) {
if (Inserted.count(I.first))
continue;
ValueMap[I.first] = I.second;
}
}
void IslNodeBuilder::createUserVector(__isl_take isl_ast_node *User,
std::vector<Value *> &IVS,
__isl_take isl_id *IteratorID,
__isl_take isl_union_map *Schedule) {
isl_ast_expr *Expr = isl_ast_node_user_get_expr(User);
isl_ast_expr *StmtExpr = isl_ast_expr_get_op_arg(Expr, 0);
isl_id *Id = isl_ast_expr_get_id(StmtExpr);
isl_ast_expr_free(StmtExpr);
ScopStmt *Stmt = (ScopStmt *)isl_id_get_user(Id);
Stmt->setAstBuild(IslAstInfo::getBuild(User));
VectorValueMapT VectorMap(IVS.size());
std::vector<LoopToScevMapT> VLTS(IVS.size());
isl_union_set *Domain = isl_union_set_from_set(Stmt->getDomain());
Schedule = isl_union_map_intersect_domain(Schedule, Domain);
isl_map *S = isl_map_from_union_map(Schedule);
createSubstitutionsVector(Expr, Stmt, VectorMap, VLTS, IVS, IteratorID);
VectorBlockGenerator::generate(BlockGen, *Stmt, VectorMap, VLTS, S);
isl_map_free(S);
isl_id_free(Id);
isl_ast_node_free(User);
}
void IslNodeBuilder::createForVector(__isl_take isl_ast_node *For,
int VectorWidth) {
isl_ast_node *Body = isl_ast_node_for_get_body(For);
isl_ast_expr *Init = isl_ast_node_for_get_init(For);
isl_ast_expr *Inc = isl_ast_node_for_get_inc(For);
isl_ast_expr *Iterator = isl_ast_node_for_get_iterator(For);
isl_id *IteratorID = isl_ast_expr_get_id(Iterator);
Value *ValueLB = ExprBuilder.create(Init);
Value *ValueInc = ExprBuilder.create(Inc);
Type *MaxType = ExprBuilder.getType(Iterator);
MaxType = ExprBuilder.getWidestType(MaxType, ValueLB->getType());
MaxType = ExprBuilder.getWidestType(MaxType, ValueInc->getType());
if (MaxType != ValueLB->getType())
ValueLB = Builder.CreateSExt(ValueLB, MaxType);
if (MaxType != ValueInc->getType())
ValueInc = Builder.CreateSExt(ValueInc, MaxType);
std::vector<Value *> IVS(VectorWidth);
IVS[0] = ValueLB;
for (int i = 1; i < VectorWidth; i++)
IVS[i] = Builder.CreateAdd(IVS[i - 1], ValueInc, "p_vector_iv");
isl_union_map *Schedule = IslAstInfo::getSchedule(For);
assert(Schedule && "For statement annotation does not contain its schedule");
IDToValue[IteratorID] = ValueLB;
switch (isl_ast_node_get_type(Body)) {
case isl_ast_node_user:
createUserVector(Body, IVS, isl_id_copy(IteratorID),
isl_union_map_copy(Schedule));
break;
case isl_ast_node_block: {
isl_ast_node_list *List = isl_ast_node_block_get_children(Body);
for (int i = 0; i < isl_ast_node_list_n_ast_node(List); ++i)
createUserVector(isl_ast_node_list_get_ast_node(List, i), IVS,
isl_id_copy(IteratorID), isl_union_map_copy(Schedule));
isl_ast_node_free(Body);
isl_ast_node_list_free(List);
break;
}
default:
isl_ast_node_dump(Body);
llvm_unreachable("Unhandled isl_ast_node in vectorizer");
}
IDToValue.erase(IDToValue.find(IteratorID));
isl_id_free(IteratorID);
isl_union_map_free(Schedule);
isl_ast_node_free(For);
isl_ast_expr_free(Iterator);
}
void IslNodeBuilder::createForSequential(__isl_take isl_ast_node *For) {
isl_ast_node *Body;
isl_ast_expr *Init, *Inc, *Iterator, *UB;
isl_id *IteratorID;
Value *ValueLB, *ValueUB, *ValueInc;
Type *MaxType;
BasicBlock *ExitBlock;
Value *IV;
CmpInst::Predicate Predicate;
bool Parallel;
Parallel =
IslAstInfo::isParallel(For) && !IslAstInfo::isReductionParallel(For);
Body = isl_ast_node_for_get_body(For);
// isl_ast_node_for_is_degenerate(For)
//
// TODO: For degenerated loops we could generate a plain assignment.
// However, for now we just reuse the logic for normal loops, which will
// create a loop with a single iteration.
Init = isl_ast_node_for_get_init(For);
Inc = isl_ast_node_for_get_inc(For);
Iterator = isl_ast_node_for_get_iterator(For);
IteratorID = isl_ast_expr_get_id(Iterator);
UB = getUpperBound(For, Predicate);
ValueLB = ExprBuilder.create(Init);
ValueUB = ExprBuilder.create(UB);
ValueInc = ExprBuilder.create(Inc);
MaxType = ExprBuilder.getType(Iterator);
MaxType = ExprBuilder.getWidestType(MaxType, ValueLB->getType());
MaxType = ExprBuilder.getWidestType(MaxType, ValueUB->getType());
MaxType = ExprBuilder.getWidestType(MaxType, ValueInc->getType());
if (MaxType != ValueLB->getType())
ValueLB = Builder.CreateSExt(ValueLB, MaxType);
if (MaxType != ValueUB->getType())
ValueUB = Builder.CreateSExt(ValueUB, MaxType);
if (MaxType != ValueInc->getType())
ValueInc = Builder.CreateSExt(ValueInc, MaxType);
// If we can show that LB <Predicate> UB holds at least once, we can
// omit the GuardBB in front of the loop.
bool UseGuardBB =
!SE.isKnownPredicate(Predicate, SE.getSCEV(ValueLB), SE.getSCEV(ValueUB));
IV = createLoop(ValueLB, ValueUB, ValueInc, Builder, P, LI, DT, ExitBlock,
Predicate, &Annotator, Parallel, UseGuardBB);
IDToValue[IteratorID] = IV;
create(Body);
Annotator.popLoop(Parallel);
IDToValue.erase(IDToValue.find(IteratorID));
Builder.SetInsertPoint(ExitBlock->begin());
isl_ast_node_free(For);
isl_ast_expr_free(Iterator);
isl_id_free(IteratorID);
}
/// @brief Remove the BBs contained in a (sub)function from the dominator tree.
///
/// This function removes the basic blocks that are part of a subfunction from
/// the dominator tree. Specifically, when generating code it may happen that at
/// some point the code generation continues in a new sub-function (e.g., when
/// generating OpenMP code). The basic blocks that are created in this
/// sub-function are then still part of the dominator tree of the original
/// function, such that the dominator tree reaches over function boundaries.
/// This is not only incorrect, but also causes crashes. This function now
/// removes from the dominator tree all basic blocks that are dominated (and
/// consequently reachable) from the entry block of this (sub)function.
///
/// FIXME: A LLVM (function or region) pass should not touch anything outside of
/// the function/region it runs on. Hence, the pure need for this function shows
/// that we do not comply to this rule. At the moment, this does not cause any
/// issues, but we should be aware that such issues may appear. Unfortunately
/// the current LLVM pass infrastructure does not allow to make Polly a module
/// or call-graph pass to solve this issue, as such a pass would not have access
/// to the per-function analyses passes needed by Polly. A future pass manager
/// infrastructure is supposed to enable such kind of access possibly allowing
/// us to create a cleaner solution here.
///
/// FIXME: Instead of adding the dominance information and then dropping it
/// later on, we should try to just not add it in the first place. This requires
/// some careful testing to make sure this does not break in interaction with
/// the SCEVBuilder and SplitBlock which may rely on the dominator tree or
/// which may try to update it.
///
/// @param F The function which contains the BBs to removed.
/// @param DT The dominator tree from which to remove the BBs.
static void removeSubFuncFromDomTree(Function *F, DominatorTree &DT) {
DomTreeNode *N = DT.getNode(&F->getEntryBlock());
std::vector<BasicBlock *> Nodes;
// We can only remove an element from the dominator tree, if all its children
// have been removed. To ensure this we obtain the list of nodes to remove
// using a post-order tree traversal.
for (po_iterator<DomTreeNode *> I = po_begin(N), E = po_end(N); I != E; ++I)
Nodes.push_back(I->getBlock());
for (BasicBlock *BB : Nodes)
DT.eraseNode(BB);
}
void IslNodeBuilder::createForParallel(__isl_take isl_ast_node *For) {
isl_ast_node *Body;
isl_ast_expr *Init, *Inc, *Iterator, *UB;
isl_id *IteratorID;
Value *ValueLB, *ValueUB, *ValueInc;
Type *MaxType;
Value *IV;
CmpInst::Predicate Predicate;
Body = isl_ast_node_for_get_body(For);
Init = isl_ast_node_for_get_init(For);
Inc = isl_ast_node_for_get_inc(For);
Iterator = isl_ast_node_for_get_iterator(For);
IteratorID = isl_ast_expr_get_id(Iterator);
UB = getUpperBound(For, Predicate);
ValueLB = ExprBuilder.create(Init);
ValueUB = ExprBuilder.create(UB);
ValueInc = ExprBuilder.create(Inc);
// OpenMP always uses SLE. In case the isl generated AST uses a SLT
// expression, we need to adjust the loop blound by one.
if (Predicate == CmpInst::ICMP_SLT)
ValueUB = Builder.CreateAdd(
ValueUB, Builder.CreateSExt(Builder.getTrue(), ValueUB->getType()));
MaxType = ExprBuilder.getType(Iterator);
MaxType = ExprBuilder.getWidestType(MaxType, ValueLB->getType());
MaxType = ExprBuilder.getWidestType(MaxType, ValueUB->getType());
MaxType = ExprBuilder.getWidestType(MaxType, ValueInc->getType());
if (MaxType != ValueLB->getType())
ValueLB = Builder.CreateSExt(ValueLB, MaxType);
if (MaxType != ValueUB->getType())
ValueUB = Builder.CreateSExt(ValueUB, MaxType);
if (MaxType != ValueInc->getType())
ValueInc = Builder.CreateSExt(ValueInc, MaxType);
BasicBlock::iterator LoopBody;
SetVector<Value *> SubtreeValues;
SetVector<const Loop *> Loops;
getReferencesInSubtree(For, SubtreeValues, Loops);
// Create for all loops we depend on values that contain the current loop
// iteration. These values are necessary to generate code for SCEVs that
// depend on such loops. As a result we need to pass them to the subfunction.
for (const Loop *L : Loops) {
const SCEV *OuterLIV = SE.getAddRecExpr(SE.getUnknown(Builder.getInt64(0)),
SE.getUnknown(Builder.getInt64(1)),
L, SCEV::FlagAnyWrap);
Value *V = generateSCEV(OuterLIV);
OutsideLoopIterations[L] = SE.getUnknown(V);
SubtreeValues.insert(V);
}
ParallelLoopGenerator::ValueToValueMapTy NewValues;
ParallelLoopGenerator ParallelLoopGen(Builder, P, LI, DT, DL);
IV = ParallelLoopGen.createParallelLoop(ValueLB, ValueUB, ValueInc,
SubtreeValues, NewValues, &LoopBody);
BasicBlock::iterator AfterLoop = Builder.GetInsertPoint();
Builder.SetInsertPoint(LoopBody);
// Save the current values.
ValueMapT ValueMapCopy = ValueMap;
IslExprBuilder::IDToValueTy IDToValueCopy = IDToValue;
updateValues(NewValues);
IDToValue[IteratorID] = IV;
create(Body);
// Restore the original values.
ValueMap = ValueMapCopy;
IDToValue = IDToValueCopy;
Builder.SetInsertPoint(AfterLoop);
removeSubFuncFromDomTree((*LoopBody).getParent()->getParent(), DT);
for (const Loop *L : Loops)
OutsideLoopIterations.erase(L);
isl_ast_node_free(For);
isl_ast_expr_free(Iterator);
isl_id_free(IteratorID);
}
void IslNodeBuilder::createFor(__isl_take isl_ast_node *For) {
bool Vector = PollyVectorizerChoice != VECTORIZER_NONE;
if (Vector && IslAstInfo::isInnermostParallel(For) &&
!IslAstInfo::isReductionParallel(For)) {
int VectorWidth = getNumberOfIterations(For);
if (1 < VectorWidth && VectorWidth <= 16) {
createForVector(For, VectorWidth);
return;
}
}
if (IslAstInfo::isExecutedInParallel(For)) {
createForParallel(For);
return;
}
createForSequential(For);
}
void IslNodeBuilder::createIf(__isl_take isl_ast_node *If) {
isl_ast_expr *Cond = isl_ast_node_if_get_cond(If);
Function *F = Builder.GetInsertBlock()->getParent();
LLVMContext &Context = F->getContext();
BasicBlock *CondBB =
SplitBlock(Builder.GetInsertBlock(), Builder.GetInsertPoint(), &DT, &LI);
CondBB->setName("polly.cond");
BasicBlock *MergeBB = SplitBlock(CondBB, CondBB->begin(), &DT, &LI);
MergeBB->setName("polly.merge");
BasicBlock *ThenBB = BasicBlock::Create(Context, "polly.then", F);
BasicBlock *ElseBB = BasicBlock::Create(Context, "polly.else", F);
DT.addNewBlock(ThenBB, CondBB);
DT.addNewBlock(ElseBB, CondBB);
DT.changeImmediateDominator(MergeBB, CondBB);
Loop *L = LI.getLoopFor(CondBB);
if (L) {
L->addBasicBlockToLoop(ThenBB, LI);
L->addBasicBlockToLoop(ElseBB, LI);
}
CondBB->getTerminator()->eraseFromParent();
Builder.SetInsertPoint(CondBB);
Value *Predicate = ExprBuilder.create(Cond);
Builder.CreateCondBr(Predicate, ThenBB, ElseBB);
Builder.SetInsertPoint(ThenBB);
Builder.CreateBr(MergeBB);
Builder.SetInsertPoint(ElseBB);
Builder.CreateBr(MergeBB);
Builder.SetInsertPoint(ThenBB->begin());
create(isl_ast_node_if_get_then(If));
Builder.SetInsertPoint(ElseBB->begin());
if (isl_ast_node_if_has_else(If))
create(isl_ast_node_if_get_else(If));
Builder.SetInsertPoint(MergeBB->begin());
isl_ast_node_free(If);
}
void IslNodeBuilder::createSubstitutions(isl_ast_expr *Expr, ScopStmt *Stmt,
ValueMapT &VMap, LoopToScevMapT &LTS) {
assert(isl_ast_expr_get_type(Expr) == isl_ast_expr_op &&
"Expression of type 'op' expected");
assert(isl_ast_expr_get_op_type(Expr) == isl_ast_op_call &&
"Opertation of type 'call' expected");
for (int i = 0; i < isl_ast_expr_get_op_n_arg(Expr) - 1; ++i) {
isl_ast_expr *SubExpr;
Value *V;
SubExpr = isl_ast_expr_get_op_arg(Expr, i + 1);
V = ExprBuilder.create(SubExpr);
ScalarEvolution *SE = Stmt->getParent()->getSE();
LTS[Stmt->getLoopForDimension(i)] = SE->getUnknown(V);
}
// Add the current ValueMap to our per-statement value map.
//
// This is needed e.g. to rewrite array base addresses when moving code
// into a parallely executed subfunction.
VMap.insert(ValueMap.begin(), ValueMap.end());
isl_ast_expr_free(Expr);
}
void IslNodeBuilder::createSubstitutionsVector(
__isl_take isl_ast_expr *Expr, ScopStmt *Stmt, VectorValueMapT &VMap,
std::vector<LoopToScevMapT> &VLTS, std::vector<Value *> &IVS,
__isl_take isl_id *IteratorID) {
int i = 0;
Value *OldValue = IDToValue[IteratorID];
for (Value *IV : IVS) {
IDToValue[IteratorID] = IV;
createSubstitutions(isl_ast_expr_copy(Expr), Stmt, VMap[i], VLTS[i]);
i++;
}
IDToValue[IteratorID] = OldValue;
isl_id_free(IteratorID);
isl_ast_expr_free(Expr);
}
void IslNodeBuilder::createUser(__isl_take isl_ast_node *User) {
ValueMapT VMap;
LoopToScevMapT LTS;
isl_id *Id;
ScopStmt *Stmt;
isl_ast_expr *Expr = isl_ast_node_user_get_expr(User);
isl_ast_expr *StmtExpr = isl_ast_expr_get_op_arg(Expr, 0);
Id = isl_ast_expr_get_id(StmtExpr);
isl_ast_expr_free(StmtExpr);
LTS.insert(OutsideLoopIterations.begin(), OutsideLoopIterations.end());
Stmt = (ScopStmt *)isl_id_get_user(Id);
Stmt->setAstBuild(IslAstInfo::getBuild(User));
createSubstitutions(Expr, Stmt, VMap, LTS);
BlockGen.copyBB(*Stmt, VMap, LTS);
isl_ast_node_free(User);
isl_id_free(Id);
}
void IslNodeBuilder::createBlock(__isl_take isl_ast_node *Block) {
isl_ast_node_list *List = isl_ast_node_block_get_children(Block);
for (int i = 0; i < isl_ast_node_list_n_ast_node(List); ++i)
create(isl_ast_node_list_get_ast_node(List, i));
isl_ast_node_free(Block);
isl_ast_node_list_free(List);
}
void IslNodeBuilder::create(__isl_take isl_ast_node *Node) {
switch (isl_ast_node_get_type(Node)) {
case isl_ast_node_error:
llvm_unreachable("code generation error");
case isl_ast_node_for:
createFor(Node);
return;
case isl_ast_node_if:
createIf(Node);
return;
case isl_ast_node_user:
createUser(Node);
return;
case isl_ast_node_block:
createBlock(Node);
return;
}
llvm_unreachable("Unknown isl_ast_node type");
}
void IslNodeBuilder::addParameters(__isl_take isl_set *Context) {
for (unsigned i = 0; i < isl_set_dim(Context, isl_dim_param); ++i) {
isl_id *Id;
Id = isl_set_get_dim_id(Context, isl_dim_param, i);
IDToValue[Id] = generateSCEV((const SCEV *)isl_id_get_user(Id));
isl_id_free(Id);
}
// Generate values for the current loop iteration for all surrounding loops.
//
// We may also reference loops outside of the scop which do not contain the
// scop itself, but as the number of such scops may be arbitrarily large we do
// not generate code for them here, but only at the point of code generation
// where these values are needed.
Region &R = S.getRegion();
Loop *L = LI.getLoopFor(R.getEntry());
while (L != nullptr && R.contains(L))
L = L->getParentLoop();
while (L != nullptr) {
const SCEV *OuterLIV = SE.getAddRecExpr(SE.getUnknown(Builder.getInt64(0)),
SE.getUnknown(Builder.getInt64(1)),
L, SCEV::FlagAnyWrap);
Value *V = generateSCEV(OuterLIV);
OutsideLoopIterations[L] = SE.getUnknown(V);
L = L->getParentLoop();
}
isl_set_free(Context);
}
Value *IslNodeBuilder::generateSCEV(const SCEV *Expr) {
Instruction *InsertLocation = --(Builder.GetInsertBlock()->end());
return Rewriter->expandCodeFor(Expr, Expr->getType(), InsertLocation);
}
namespace {
class IslCodeGeneration : public ScopPass {
public:
static char ID;
IslCodeGeneration() : ScopPass(ID) {}
/// @brief The datalayout used
const DataLayout *DL;
/// @name The analysis passes we need to generate code.
///
///{
LoopInfo *LI;
IslAstInfo *AI;
DominatorTree *DT;
ScalarEvolution *SE;
///}
/// @brief The loop annotator to generate llvm.loop metadata.
ScopAnnotator Annotator;
/// @brief Build the runtime condition.
///
/// Build the condition that evaluates at run-time to true iff all
/// assumptions taken for the SCoP hold, and to false otherwise.
///
/// @return A value evaluating to true/false if execution is save/unsafe.
Value *buildRTC(PollyIRBuilder &Builder, IslExprBuilder &ExprBuilder) {
Builder.SetInsertPoint(Builder.GetInsertBlock()->getTerminator());
Value *RTC = ExprBuilder.create(AI->getRunCondition());
if (!RTC->getType()->isIntegerTy(1))
RTC = Builder.CreateIsNotNull(RTC);
return RTC;
}
bool runOnScop(Scop &S) {
AI = &getAnalysis<IslAstInfo>();
// Check if we created an isl_ast root node, otherwise exit.
isl_ast_node *AstRoot = AI->getAst();
if (!AstRoot)
return false;
LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
SE = &getAnalysis<ScalarEvolution>();
DL = &getAnalysis<DataLayoutPass>().getDataLayout();
assert(!S.getRegion().isTopLevelRegion() &&
"Top level regions are not supported");
// Build the alias scopes for annotations first.
if (PollyAnnotateAliasScopes)
Annotator.buildAliasScopes(S);
BasicBlock *EnteringBB = simplifyRegion(&S, this);
PollyIRBuilder Builder = createPollyIRBuilder(EnteringBB, Annotator);
IslNodeBuilder NodeBuilder(Builder, Annotator, this, *DL, *LI, *SE, *DT, S);
NodeBuilder.addParameters(S.getContext());
Value *RTC = buildRTC(Builder, NodeBuilder.getExprBuilder());
BasicBlock *StartBlock = executeScopConditionally(S, this, RTC);
Builder.SetInsertPoint(StartBlock->begin());
NodeBuilder.create(AstRoot);
return true;
}
virtual void printScop(raw_ostream &OS) const {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DataLayoutPass>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<IslAstInfo>();
AU.addRequired<RegionInfoPass>();
AU.addRequired<ScalarEvolution>();
AU.addRequired<ScopDetection>();
AU.addRequired<ScopInfo>();
AU.addRequired<LoopInfoWrapperPass>();
AU.addPreserved<Dependences>();
AU.addPreserved<LoopInfoWrapperPass>();
AU.addPreserved<DominatorTreeWrapperPass>();
AU.addPreserved<IslAstInfo>();
AU.addPreserved<ScopDetection>();
AU.addPreserved<ScalarEvolution>();
// FIXME: We do not yet add regions for the newly generated code to the
// region tree.
AU.addPreserved<RegionInfoPass>();
AU.addPreserved<TempScopInfo>();
AU.addPreserved<ScopInfo>();
AU.addPreservedID(IndependentBlocksID);
}
};
}
char IslCodeGeneration::ID = 1;
Pass *polly::createIslCodeGenerationPass() { return new IslCodeGeneration(); }
INITIALIZE_PASS_BEGIN(IslCodeGeneration, "polly-codegen-isl",
"Polly - Create LLVM-IR from SCoPs", false, false);
INITIALIZE_PASS_DEPENDENCY(Dependences);
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass);
INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass);
INITIALIZE_PASS_DEPENDENCY(RegionInfoPass);
INITIALIZE_PASS_DEPENDENCY(ScalarEvolution);
INITIALIZE_PASS_DEPENDENCY(ScopDetection);
INITIALIZE_PASS_END(IslCodeGeneration, "polly-codegen-isl",
"Polly - Create LLVM-IR from SCoPs", false, false)
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