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llvm-project/polly/lib/Support/ScopHelper.cpp
Johannes Doerfert f80f3b0449 Allow user defined error functions 
The user can provide function names with
    -polly-error-functions=name1,name2,name3
  that will be treated as error functions. Any call to them is assumed
  not to be executed.

  This feature is mainly for developers to play around with the new
  "error block" feature.

llvm-svn: 249098
2015-10-01 23:45:51 +00:00

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//===- ScopHelper.cpp - Some Helper Functions for Scop. ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Small functions that help with Scop and LLVM-IR.
//
//===----------------------------------------------------------------------===//
#include "polly/Support/ScopHelper.h"
#include "polly/Options.h"
#include "polly/ScopInfo.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/RegionInfo.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpander.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/IR/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
using namespace polly;
#define DEBUG_TYPE "polly-scop-helper"
static cl::list<std::string>
ErrorFunctions("polly-error-functions",
cl::desc("A list of error functions"), cl::Hidden,
cl::ZeroOrMore, cl::CommaSeparated, cl::cat(PollyCategory));
Value *polly::getPointerOperand(Instruction &Inst) {
if (LoadInst *load = dyn_cast<LoadInst>(&Inst))
return load->getPointerOperand();
else if (StoreInst *store = dyn_cast<StoreInst>(&Inst))
return store->getPointerOperand();
else if (GetElementPtrInst *gep = dyn_cast<GetElementPtrInst>(&Inst))
return gep->getPointerOperand();
return 0;
}
bool polly::hasInvokeEdge(const PHINode *PN) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i)
if (InvokeInst *II = dyn_cast<InvokeInst>(PN->getIncomingValue(i)))
if (II->getParent() == PN->getIncomingBlock(i))
return true;
return false;
}
// Ensures that there is just one predecessor to the entry node from outside the
// region.
// The identity of the region entry node is preserved.
static void simplifyRegionEntry(Region *R, DominatorTree *DT, LoopInfo *LI,
RegionInfo *RI) {
BasicBlock *EnteringBB = R->getEnteringBlock();
BasicBlock *Entry = R->getEntry();
// Before (one of):
//
// \ / //
// EnteringBB //
// | \------> //
// \ / | //
// Entry <--\ Entry <--\ //
// / \ / / \ / //
// .... .... //
// Create single entry edge if the region has multiple entry edges.
if (!EnteringBB) {
SmallVector<BasicBlock *, 4> Preds;
for (BasicBlock *P : predecessors(Entry))
if (!R->contains(P))
Preds.push_back(P);
BasicBlock *NewEntering =
SplitBlockPredecessors(Entry, Preds, ".region_entering", DT, LI);
if (RI) {
// The exit block of predecessing regions must be changed to NewEntering
for (BasicBlock *ExitPred : predecessors(NewEntering)) {
Region *RegionOfPred = RI->getRegionFor(ExitPred);
if (RegionOfPred->getExit() != Entry)
continue;
while (!RegionOfPred->isTopLevelRegion() &&
RegionOfPred->getExit() == Entry) {
RegionOfPred->replaceExit(NewEntering);
RegionOfPred = RegionOfPred->getParent();
}
}
// Make all ancestors use EnteringBB as entry; there might be edges to it
Region *AncestorR = R->getParent();
RI->setRegionFor(NewEntering, AncestorR);
while (!AncestorR->isTopLevelRegion() && AncestorR->getEntry() == Entry) {
AncestorR->replaceEntry(NewEntering);
AncestorR = AncestorR->getParent();
}
}
EnteringBB = NewEntering;
}
assert(R->getEnteringBlock() == EnteringBB);
// After:
//
// \ / //
// EnteringBB //
// | //
// | //
// Entry <--\ //
// / \ / //
// .... //
}
// Ensure that the region has a single block that branches to the exit node.
static void simplifyRegionExit(Region *R, DominatorTree *DT, LoopInfo *LI,
RegionInfo *RI) {
BasicBlock *ExitBB = R->getExit();
BasicBlock *ExitingBB = R->getExitingBlock();
// Before:
//
// (Region) ______/ //
// \ | / //
// ExitBB //
// / \ //
if (!ExitingBB) {
SmallVector<BasicBlock *, 4> Preds;
for (BasicBlock *P : predecessors(ExitBB))
if (R->contains(P))
Preds.push_back(P);
// Preds[0] Preds[1] otherBB //
// \ | ________/ //
// \ | / //
// BB //
ExitingBB =
SplitBlockPredecessors(ExitBB, Preds, ".region_exiting", DT, LI);
// Preds[0] Preds[1] otherBB //
// \ / / //
// BB.region_exiting / //
// \ / //
// BB //
if (RI)
RI->setRegionFor(ExitingBB, R);
// Change the exit of nested regions, but not the region itself,
R->replaceExitRecursive(ExitingBB);
R->replaceExit(ExitBB);
}
assert(ExitingBB == R->getExitingBlock());
// After:
//
// \ / //
// ExitingBB _____/ //
// \ / //
// ExitBB //
// / \ //
}
void polly::simplifyRegion(Region *R, DominatorTree *DT, LoopInfo *LI,
RegionInfo *RI) {
assert(R && !R->isTopLevelRegion());
assert(!RI || RI == R->getRegionInfo());
assert((!RI || DT) &&
"RegionInfo requires DominatorTree to be updated as well");
simplifyRegionEntry(R, DT, LI, RI);
simplifyRegionExit(R, DT, LI, RI);
assert(R->isSimple());
}
// Split the block into two successive blocks.
//
// Like llvm::SplitBlock, but also preserves RegionInfo
static BasicBlock *splitBlock(BasicBlock *Old, Instruction *SplitPt,
DominatorTree *DT, llvm::LoopInfo *LI,
RegionInfo *RI) {
assert(Old && SplitPt);
// Before:
//
// \ / //
// Old //
// / \ //
BasicBlock *NewBlock = llvm::SplitBlock(Old, SplitPt, DT, LI);
if (RI) {
Region *R = RI->getRegionFor(Old);
RI->setRegionFor(NewBlock, R);
}
// After:
//
// \ / //
// Old //
// | //
// NewBlock //
// / \ //
return NewBlock;
}
void polly::splitEntryBlockForAlloca(BasicBlock *EntryBlock, Pass *P) {
// Find first non-alloca instruction. Every basic block has a non-alloc
// instruction, as every well formed basic block has a terminator.
BasicBlock::iterator I = EntryBlock->begin();
while (isa<AllocaInst>(I))
++I;
auto *DTWP = P->getAnalysisIfAvailable<DominatorTreeWrapperPass>();
auto *DT = DTWP ? &DTWP->getDomTree() : nullptr;
auto *LIWP = P->getAnalysisIfAvailable<LoopInfoWrapperPass>();
auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
RegionInfoPass *RIP = P->getAnalysisIfAvailable<RegionInfoPass>();
RegionInfo *RI = RIP ? &RIP->getRegionInfo() : nullptr;
// splitBlock updates DT, LI and RI.
splitBlock(EntryBlock, I, DT, LI, RI);
}
/// The SCEVExpander will __not__ generate any code for an existing SDiv/SRem
/// instruction but just use it, if it is referenced as a SCEVUnknown. We want
/// however to generate new code if the instruction is in the analyzed region
/// and we generate code outside/in front of that region. Hence, we generate the
/// code for the SDiv/SRem operands in front of the analyzed region and then
/// create a new SDiv/SRem operation there too.
struct ScopExpander : SCEVVisitor<ScopExpander, const SCEV *> {
friend struct SCEVVisitor<ScopExpander, const SCEV *>;
explicit ScopExpander(const Region &R, ScalarEvolution &SE,
const DataLayout &DL, const char *Name, ValueMapT *VMap)
: Expander(SCEVExpander(SE, DL, Name)), SE(SE), Name(Name), R(R),
VMap(VMap) {}
Value *expandCodeFor(const SCEV *E, Type *Ty, Instruction *I) {
// If we generate code in the region we will immediately fall back to the
// SCEVExpander, otherwise we will stop at all unknowns in the SCEV and if
// needed replace them by copies computed in the entering block.
if (!R.contains(I))
E = visit(E);
return Expander.expandCodeFor(E, Ty, I);
}
private:
SCEVExpander Expander;
ScalarEvolution &SE;
const char *Name;
const Region &R;
ValueMapT *VMap;
const SCEV *visitUnknown(const SCEVUnknown *E) {
// If a value mapping was given try if the underlying value is remapped.
if (VMap)
if (Value *NewVal = VMap->lookup(E->getValue()))
if (NewVal != E->getValue())
return visit(SE.getSCEV(NewVal));
Instruction *Inst = dyn_cast<Instruction>(E->getValue());
if (!Inst || (Inst->getOpcode() != Instruction::SRem &&
Inst->getOpcode() != Instruction::SDiv))
return E;
if (!R.contains(Inst))
return E;
Instruction *StartIP = R.getEnteringBlock()->getTerminator();
const SCEV *LHSScev = visit(SE.getSCEV(Inst->getOperand(0)));
const SCEV *RHSScev = visit(SE.getSCEV(Inst->getOperand(1)));
Value *LHS = Expander.expandCodeFor(LHSScev, E->getType(), StartIP);
Value *RHS = Expander.expandCodeFor(RHSScev, E->getType(), StartIP);
Inst = BinaryOperator::Create((Instruction::BinaryOps)Inst->getOpcode(),
LHS, RHS, Inst->getName() + Name, StartIP);
return SE.getSCEV(Inst);
}
/// The following functions will just traverse the SCEV and rebuild it with
/// the new operands returned by the traversal.
///
///{
const SCEV *visitConstant(const SCEVConstant *E) { return E; }
const SCEV *visitTruncateExpr(const SCEVTruncateExpr *E) {
return SE.getTruncateExpr(visit(E->getOperand()), E->getType());
}
const SCEV *visitZeroExtendExpr(const SCEVZeroExtendExpr *E) {
return SE.getZeroExtendExpr(visit(E->getOperand()), E->getType());
}
const SCEV *visitSignExtendExpr(const SCEVSignExtendExpr *E) {
return SE.getSignExtendExpr(visit(E->getOperand()), E->getType());
}
const SCEV *visitUDivExpr(const SCEVUDivExpr *E) {
return SE.getUDivExpr(visit(E->getLHS()), visit(E->getRHS()));
}
const SCEV *visitAddExpr(const SCEVAddExpr *E) {
SmallVector<const SCEV *, 4> NewOps;
for (const SCEV *Op : E->operands())
NewOps.push_back(visit(Op));
return SE.getAddExpr(NewOps);
}
const SCEV *visitMulExpr(const SCEVMulExpr *E) {
SmallVector<const SCEV *, 4> NewOps;
for (const SCEV *Op : E->operands())
NewOps.push_back(visit(Op));
return SE.getMulExpr(NewOps);
}
const SCEV *visitUMaxExpr(const SCEVUMaxExpr *E) {
SmallVector<const SCEV *, 4> NewOps;
for (const SCEV *Op : E->operands())
NewOps.push_back(visit(Op));
return SE.getUMaxExpr(NewOps);
}
const SCEV *visitSMaxExpr(const SCEVSMaxExpr *E) {
SmallVector<const SCEV *, 4> NewOps;
for (const SCEV *Op : E->operands())
NewOps.push_back(visit(Op));
return SE.getSMaxExpr(NewOps);
}
const SCEV *visitAddRecExpr(const SCEVAddRecExpr *E) {
SmallVector<const SCEV *, 4> NewOps;
for (const SCEV *Op : E->operands())
NewOps.push_back(visit(Op));
return SE.getAddRecExpr(NewOps, E->getLoop(), E->getNoWrapFlags());
}
///}
};
Value *polly::expandCodeFor(Scop &S, ScalarEvolution &SE, const DataLayout &DL,
const char *Name, const SCEV *E, Type *Ty,
Instruction *IP, ValueMapT *VMap) {
ScopExpander Expander(S.getRegion(), SE, DL, Name, VMap);
return Expander.expandCodeFor(E, Ty, IP);
}
bool polly::isErrorBlock(BasicBlock &BB) {
if (isa<UnreachableInst>(BB.getTerminator()))
return true;
if (ErrorFunctions.empty())
return false;
for (Instruction &Inst : BB)
if (CallInst *CI = dyn_cast<CallInst>(&Inst))
if (Function *F = CI->getCalledFunction()) {
const auto &FnName = F->getName();
for (const auto &ErrorFn : ErrorFunctions)
if (FnName.equals(ErrorFn))
return true;
}
return false;
}
Value *polly::getConditionFromTerminator(TerminatorInst *TI) {
if (BranchInst *BR = dyn_cast<BranchInst>(TI)) {
if (BR->isUnconditional())
return ConstantInt::getTrue(Type::getInt1Ty(TI->getContext()));
return BR->getCondition();
}
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI))
return SI->getCondition();
return nullptr;
}
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