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Allow switch instructions in SCoPs
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  This patch allows switch instructions with affine conditions in the
  SCoP. Also switch instructions in non-affine subregions are allowed.
  Both did not require much changes to the code, though there was some
  refactoring needed to integrate them without code duplication.

  In the llvm-test suite the number of profitable SCoPs increased from
  135 to 139 but more importantly we can handle more benchmarks and user
  inputs without preprocessing.

Differential Revision: http://reviews.llvm.org/D13200

llvm-svn: 248701
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Johannes Doerfert committed Sep 28, 2015
1 parent 3d77768 commit 9a132f3
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Showing 17 changed files with 1,126 additions and 65 deletions.
22 changes: 22 additions & 0 deletions polly/include/polly/ScopDetection.h
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Expand Up @@ -271,6 +271,28 @@ class ScopDetection : public FunctionPass {
/// @return True if the instruction is valid, false otherwise.
bool isValidInstruction(Instruction &Inst, DetectionContext &Context) const;

/// @brief Check if the switch @p SI with condition @p Condition is valid.
///
/// @param BB The block to check.
/// @param SI The switch to check.
/// @param Condition The switch condition.
/// @param Context The context of scop detection.
///
/// @return True if the branch @p BI is valid.
bool isValidSwitch(BasicBlock &BB, SwitchInst *SI, Value *Condition,
DetectionContext &Context) const;

/// @brief Check if the branch @p BI with condition @p Condition is valid.
///
/// @param BB The block to check.
/// @param BI The branch to check.
/// @param Condition The branch condition.
/// @param Context The context of scop detection.
///
/// @return True if the branch @p BI is valid.
bool isValidBranch(BasicBlock &BB, BranchInst *BI, Value *Condition,
DetectionContext &Context) const;

/// @brief Check if the control flow in a basic block is valid.
///
/// @param BB The BB to check the control flow.
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10 changes: 5 additions & 5 deletions polly/include/polly/ScopDetectionDiagnostic.h
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Expand Up @@ -62,7 +62,7 @@ void emitValidRemarks(const llvm::Function &F, const Region *R);
enum RejectReasonKind {
// CFG Category
rrkCFG,
rrkNonBranchTerminator,
rrkInvalidTerminator,
rrkCondition,
rrkLastCFG,

Expand Down Expand Up @@ -230,13 +230,13 @@ class ReportCFG : public RejectReason {
};

//===----------------------------------------------------------------------===//
/// @brief Captures a non-branch terminator within a Scop candidate.
class ReportNonBranchTerminator : public ReportCFG {
/// @brief Captures bad terminator within a Scop candidate.
class ReportInvalidTerminator : public ReportCFG {
BasicBlock *BB;

public:
ReportNonBranchTerminator(BasicBlock *BB)
: ReportCFG(rrkNonBranchTerminator), BB(BB) {}
ReportInvalidTerminator(BasicBlock *BB)
: ReportCFG(rrkInvalidTerminator), BB(BB) {}

/// @name LLVM-RTTI interface
//@{
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10 changes: 10 additions & 0 deletions polly/include/polly/Support/ScopHelper.h
View file
Expand Up @@ -30,6 +30,7 @@ class StringRef;
class DataLayout;
class DominatorTree;
class RegionInfo;
class TerminatorInst;
class ScalarEvolution;
}

Expand Down Expand Up @@ -113,5 +114,14 @@ llvm::Value *expandCodeFor(Scop &S, llvm::ScalarEvolution &SE,
///
/// @return True if the block is a error block, false otherwise.
bool isErrorBlock(llvm::BasicBlock &BB);

/// @brief Return the condition for the terminator @p TI.
///
/// For unconditional branches the "i1 true" condition will be returned.
///
/// @param TI The terminator to get the condition from.
///
/// @return The condition of @p TI and nullptr if none could be extracted.
llvm::Value *getConditionFromTerminator(llvm::TerminatorInst *TI);
}
#endif
77 changes: 52 additions & 25 deletions polly/lib/Analysis/ScopDetection.cpp
View file
Expand Up @@ -299,48 +299,43 @@ bool ScopDetection::addOverApproximatedRegion(Region *AR,
return (AllowNonAffineSubLoops || Context.BoxedLoopsSet.empty());
}

bool ScopDetection::isValidCFG(BasicBlock &BB,
DetectionContext &Context) const {
bool ScopDetection::isValidSwitch(BasicBlock &BB, SwitchInst *SI,
Value *Condition,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;

TerminatorInst *TI = BB.getTerminator();

// Return instructions are only valid if the region is the top level region.
if (isa<ReturnInst>(TI) && !CurRegion.getExit() && TI->getNumOperands() == 0)
return true;

BranchInst *Br = dyn_cast<BranchInst>(TI);
Loop *L = LI->getLoopFor(&BB);
const SCEV *ConditionSCEV = SE->getSCEVAtScope(Condition, L);

if (!Br)
return invalid<ReportNonBranchTerminator>(Context, /*Assert=*/true, &BB);

if (Br->isUnconditional())
return true;
if (!isAffineExpr(&CurRegion, ConditionSCEV, *SE))
if (!AllowNonAffineSubRegions ||
!addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return invalid<ReportNonAffBranch>(Context, /*Assert=*/true, &BB,
ConditionSCEV, ConditionSCEV, SI);

Value *Condition = Br->getCondition();
return true;
}

// UndefValue is not allowed as condition.
if (isa<UndefValue>(Condition))
return invalid<ReportUndefCond>(Context, /*Assert=*/true, Br, &BB);
bool ScopDetection::isValidBranch(BasicBlock &BB, BranchInst *BI,
Value *Condition,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;

// Only Constant and ICmpInst are allowed as condition.
if (!(isa<Constant>(Condition) || isa<ICmpInst>(Condition))) {
// Non constant conditions of branches need to be ICmpInst.
if (!isa<ICmpInst>(Condition)) {
if (!AllowNonAffineSubRegions ||
!addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return invalid<ReportInvalidCond>(Context, /*Assert=*/true, Br, &BB);
return invalid<ReportInvalidCond>(Context, /*Assert=*/true, BI, &BB);
}

// Allow perfectly nested conditions.
assert(Br->getNumSuccessors() == 2 && "Unexpected number of successors");

if (ICmpInst *ICmp = dyn_cast<ICmpInst>(Condition)) {
// Unsigned comparisons are not allowed. They trigger overflow problems
// in the code generation.
//
// TODO: This is not sufficient and just hides bugs. However it does pretty
// well.
if (ICmp->isUnsigned() && !AllowUnsigned)
return invalid<ReportUnsignedCond>(Context, /*Assert=*/true, Br, &BB);
return invalid<ReportUnsignedCond>(Context, /*Assert=*/true, BI, &BB);

// Are both operands of the ICmp affine?
if (isa<UndefValue>(ICmp->getOperand(0)) ||
Expand Down Expand Up @@ -369,6 +364,38 @@ bool ScopDetection::isValidCFG(BasicBlock &BB,
return true;
}

bool ScopDetection::isValidCFG(BasicBlock &BB,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;

TerminatorInst *TI = BB.getTerminator();

// Return instructions are only valid if the region is the top level region.
if (isa<ReturnInst>(TI) && !CurRegion.getExit() && TI->getNumOperands() == 0)
return true;

Value *Condition = getConditionFromTerminator(TI);

if (!Condition)
return invalid<ReportInvalidTerminator>(Context, /*Assert=*/true, &BB);

// UndefValue is not allowed as condition.
if (isa<UndefValue>(Condition))
return invalid<ReportUndefCond>(Context, /*Assert=*/true, TI, &BB);

// Constant conditions are always affine.
if (isa<Constant>(Condition))
return true;

if (BranchInst *BI = dyn_cast<BranchInst>(TI))
return isValidBranch(BB, BI, Condition, Context);

SwitchInst *SI = dyn_cast<SwitchInst>(TI);
assert(SI && "Terminator was neither branch nor switch");

return isValidSwitch(BB, SI, Condition, Context);
}

bool ScopDetection::isValidCallInst(CallInst &CI) {
if (CI.doesNotReturn())
return false;
Expand Down
12 changes: 6 additions & 6 deletions polly/lib/Analysis/ScopDetectionDiagnostic.cpp
View file
Expand Up @@ -141,18 +141,18 @@ bool ReportCFG::classof(const RejectReason *RR) {
}

//===----------------------------------------------------------------------===//
// ReportNonBranchTerminator.
// ReportInvalidTerminator.

std::string ReportNonBranchTerminator::getMessage() const {
return ("Non branch instruction terminates BB: " + BB->getName()).str();
std::string ReportInvalidTerminator::getMessage() const {
return ("Invalid instruction terminates BB: " + BB->getName()).str();
}

const DebugLoc &ReportNonBranchTerminator::getDebugLoc() const {
const DebugLoc &ReportInvalidTerminator::getDebugLoc() const {
return BB->getTerminator()->getDebugLoc();
}

bool ReportNonBranchTerminator::classof(const RejectReason *RR) {
return RR->getKind() == rrkNonBranchTerminator;
bool ReportInvalidTerminator::classof(const RejectReason *RR) {
return RR->getKind() == rrkInvalidTerminator;
}

//===----------------------------------------------------------------------===//
Expand Down

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