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[ScopDetect/Info] Look through PHIs that follow an error block 

In case a PHI node follows an error block we can assume that the incoming value
can only come from the node that is not an error block. As a result, conditions
that seemed non-affine before are now in fact affine.

llvm-svn: 312410
This commit is contained in:
Tobias Grosser 2017-09-02 08:25:55 +00:00
parent f1f9c34174
commit 4baedc70d1
7 changed files with 134 additions and 23 deletions
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13
polly/include/polly/ScopInfo.h
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@ -1699,6 +1699,7 @@ private:
friend class ScopBuilder;
ScalarEvolution *SE;
DominatorTree *DT;
/// The underlying Region.
Region &R;
@ -1927,12 +1928,9 @@ private:
static int getNextID(std::string ParentFunc);
/// Scop constructor; invoked from ScopBuilder::buildScop.
Scop(Region &R, ScalarEvolution &SE, LoopInfo &LI,
Scop(Region &R, ScalarEvolution &SE, LoopInfo &LI, DominatorTree &DT,
ScopDetection::DetectionContext &DC, OptimizationRemarkEmitter &ORE);
/// Return the LoopInfo used for this Scop.
LoopInfo *getLI() const { return Affinator.getLI(); }
//@}
/// Initialize this ScopBuilder.
@ -2402,8 +2400,15 @@ public:
/// Remove the metadata stored for @p Access.
void removeAccessData(MemoryAccess *Access);
/// Return the scalar evolution.
ScalarEvolution *getSE() const;
/// Return the dominator tree.
DominatorTree *getDT() const { return DT; }
/// Return the LoopInfo used for this Scop.
LoopInfo *getLI() const { return Affinator.getLI(); }
/// Get the count of parameters used in this Scop.
///
/// @return The count of parameters used in this Scop.

11
polly/include/polly/Support/SCEVValidator.h
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@ -94,6 +94,17 @@ ParameterSetTy getParamsInAffineExpr(const llvm::Region *R, llvm::Loop *Scope,
/// @returns The constant factor in @p M and the rest of @p M.
std::pair<const llvm::SCEVConstant *, const llvm::SCEV *>
extractConstantFactor(const llvm::SCEV *M, llvm::ScalarEvolution &SE);
/// Try to look through PHI nodes, where some incoming edges come from error
/// blocks.
///
/// In case a PHI node follows an error block we can assume that the incoming
/// value can only come from the node that is not an error block. As a result,
/// conditions that seemed non-affine before are now in fact affine.
const llvm::SCEV *tryForwardThroughPHI(const llvm::SCEV *Expr, llvm::Region &R,
llvm::ScalarEvolution &SE,
llvm::LoopInfo &LI,
const llvm::DominatorTree &DT);
} // namespace polly
#endif

2
polly/lib/Analysis/ScopBuilder.cpp
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@ -1181,7 +1181,7 @@ static inline BasicBlock *getRegionNodeBasicBlock(RegionNode *RN) {
void ScopBuilder::buildScop(Region &R, AssumptionCache &AC,
OptimizationRemarkEmitter &ORE) {
scop.reset(new Scop(R, SE, LI, *SD.getDetectionContext(&R), ORE));
scop.reset(new Scop(R, SE, LI, DT, *SD.getDetectionContext(&R), ORE));
buildStmts(R);
buildAccessFunctions();

3
polly/lib/Analysis/ScopDetection.cpp
View File

@ -607,6 +607,9 @@ bool ScopDetection::isValidBranch(BasicBlock &BB, BranchInst *BI,
const SCEV *LHS = SE.getSCEVAtScope(ICmp->getOperand(0), L);
const SCEV *RHS = SE.getSCEVAtScope(ICmp->getOperand(1), L);
LHS = tryForwardThroughPHI(LHS, Context.CurRegion, SE, LI, DT);
RHS = tryForwardThroughPHI(RHS, Context.CurRegion, SE, LI, DT);
// If unsigned operations are not allowed try to approximate the region.
if (ICmp->isUnsigned() && !PollyAllowUnsignedOperations)
return !IsLoopBranch && AllowNonAffineSubRegions &&

41
polly/lib/Analysis/ScopInfo.cpp
View File

@ -1451,11 +1451,10 @@ getPwAff(Scop &S, BasicBlock *BB,
/// This will fill @p ConditionSets with the conditions under which control
/// will be moved from @p SI to its successors. Hence, @p ConditionSets will
/// have as many elements as @p SI has successors.
static bool
buildConditionSets(Scop &S, BasicBlock *BB, SwitchInst *SI, Loop *L,
__isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
bool buildConditionSets(Scop &S, BasicBlock *BB, SwitchInst *SI, Loop *L,
__isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
Value *Condition = getConditionFromTerminator(SI);
assert(Condition && "No condition for switch");
@ -1497,7 +1496,7 @@ buildConditionSets(Scop &S, BasicBlock *BB, SwitchInst *SI, Loop *L,
/// @param IsStrictUpperBound holds information on the predicate relation
/// between TestVal and UpperBound, i.e,
/// TestVal < UpperBound OR TestVal <= UpperBound
static __isl_give isl_set *
__isl_give isl_set *
buildUnsignedConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
__isl_keep isl_set *Domain, const SCEV *SCEV_TestVal,
const SCEV *SCEV_UpperBound,
@ -1537,11 +1536,10 @@ buildUnsignedConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
/// have as many elements as @p TI has successors. If @p TI is nullptr the
/// context under which @p Condition is true/false will be returned as the
/// new elements of @p ConditionSets.
static bool
buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
TerminatorInst *TI, Loop *L, __isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
bool buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
TerminatorInst *TI, Loop *L, __isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
isl_set *ConsequenceCondSet = nullptr;
if (auto *CCond = dyn_cast<ConstantInt>(Condition)) {
if (CCond->isZero())
@ -1577,6 +1575,10 @@ buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
"Condition of exiting branch was neither constant nor ICmp!");
ScalarEvolution &SE = *S.getSE();
LoopInfo &LI = *S.getLI();
DominatorTree &DT = *S.getDT();
Region &R = S.getRegion();
isl_pw_aff *LHS, *RHS;
// For unsigned comparisons we assumed the signed bit of neither operand
// to be set. The comparison is equal to a signed comparison under this
@ -1585,6 +1587,9 @@ buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
const SCEV *LeftOperand = SE.getSCEVAtScope(ICond->getOperand(0), L),
*RightOperand = SE.getSCEVAtScope(ICond->getOperand(1), L);
LeftOperand = tryForwardThroughPHI(LeftOperand, R, SE, LI, DT);
RightOperand = tryForwardThroughPHI(RightOperand, R, SE, LI, DT);
switch (ICond->getPredicate()) {
case ICmpInst::ICMP_ULT:
ConsequenceCondSet =
@ -1653,11 +1658,10 @@ buildConditionSets(Scop &S, BasicBlock *BB, Value *Condition,
/// This will fill @p ConditionSets with the conditions under which control
/// will be moved from @p TI to its successors. Hence, @p ConditionSets will
/// have as many elements as @p TI has successors.
static bool
buildConditionSets(Scop &S, BasicBlock *BB, TerminatorInst *TI, Loop *L,
__isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
bool buildConditionSets(Scop &S, BasicBlock *BB, TerminatorInst *TI, Loop *L,
__isl_keep isl_set *Domain,
DenseMap<BasicBlock *, isl::set> &InvalidDomainMap,
SmallVectorImpl<__isl_give isl_set *> &ConditionSets) {
if (SwitchInst *SI = dyn_cast<SwitchInst>(TI))
return buildConditionSets(S, BB, SI, L, Domain, InvalidDomainMap,
ConditionSets);
@ -3357,8 +3361,9 @@ int Scop::getNextID(std::string ParentFunc) {
}
Scop::Scop(Region &R, ScalarEvolution &ScalarEvolution, LoopInfo &LI,
ScopDetection::DetectionContext &DC, OptimizationRemarkEmitter &ORE)
: SE(&ScalarEvolution), R(R), name(R.getNameStr()),
DominatorTree &DT, ScopDetection::DetectionContext &DC,
OptimizationRemarkEmitter &ORE)
: SE(&ScalarEvolution), DT(&DT), R(R), name(R.getNameStr()),
HasSingleExitEdge(R.getExitingBlock()), DC(DC), ORE(ORE),
IslCtx(isl_ctx_alloc(), isl_ctx_free), Affinator(this, LI),
ID(getNextID((*R.getEntry()->getParent()).getName().str())) {

26
polly/lib/Support/SCEVValidator.cpp
View File

@ -735,4 +735,30 @@ extractConstantFactor(const SCEV *S, ScalarEvolution &SE) {
return std::make_pair(ConstPart, SE.getMulExpr(LeftOvers));
}
const SCEV *tryForwardThroughPHI(const SCEV *Expr, Region &R,
ScalarEvolution &SE, LoopInfo &LI,
const DominatorTree &DT) {
if (auto *Unknown = dyn_cast<SCEVUnknown>(Expr)) {
Value *V = Unknown->getValue();
auto *PHI = dyn_cast<PHINode>(V);
if (!PHI)
return Expr;
Value *Final = nullptr;
for (unsigned i = 0; i < PHI->getNumIncomingValues(); i++) {
if (isErrorBlock(*PHI->getIncomingBlock(i), R, LI, DT))
continue;
if (Final)
return Expr;
Final = PHI->getIncomingValue(i);
}
if (Final)
return SE.getSCEV(Final);
}
return Expr;
}
} // namespace polly

61
polly/test/ScopInfo/phi_after_error_block.ll Normal file
View File

@ -0,0 +1,61 @@
; RUN: opt %loadPolly -polly-scops -analyze < %s | FileCheck %s
declare void @bar()
define void @foo(float* %A, i64 %p) {
start:
br label %next
next:
%cmpA = icmp sle i64 %p, 0
br i1 %cmpA, label %error, label %ok
error:
call void @bar()
br label %merge
ok:
br label %merge
merge:
%phi = phi i64 [0, %error], [1, %ok]
store float 42.0, float* %A
%cmp = icmp eq i64 %phi, %p
br i1 %cmp, label %loop, label %exit
loop:
%indvar = phi i64 [0, %merge], [%indvar.next, %loop]
store float 42.0, float* %A
%indvar.next = add i64 %indvar, 1
%cmp2 = icmp sle i64 %indvar, 1024
br i1 %cmp2, label %loop, label %exit
exit:
ret void
}
; CHECK: Statements {
; CHECK-NEXT: Stmt_ok
; CHECK-NEXT: Domain :=
; CHECK-NEXT: [p] -> { Stmt_ok[] : p > 0 };
; CHECK-NEXT: Schedule :=
; CHECK-NEXT: [p] -> { Stmt_ok[] -> [0, 0] };
; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 1]
; CHECK-NEXT: [p] -> { Stmt_ok[] -> MemRef_phi__phi[] };
; CHECK-NEXT: Stmt_merge
; CHECK-NEXT: Domain :=
; CHECK-NEXT: [p] -> { Stmt_merge[] };
; CHECK-NEXT: Schedule :=
; CHECK-NEXT: [p] -> { Stmt_merge[] -> [1, 0] };
; CHECK-NEXT: ReadAccess := [Reduction Type: NONE] [Scalar: 1]
; CHECK-NEXT: [p] -> { Stmt_merge[] -> MemRef_phi__phi[] };
; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
; CHECK-NEXT: [p] -> { Stmt_merge[] -> MemRef_A[0] };
; CHECK-NEXT: Stmt_loop
; CHECK-NEXT: Domain :=
; CHECK-NEXT: [p] -> { Stmt_loop[i0] : p = 1 and 0 <= i0 <= 1025 };
; CHECK-NEXT: Schedule :=
; CHECK-NEXT: [p] -> { Stmt_loop[i0] -> [2, i0] };
; CHECK-NEXT: MustWriteAccess := [Reduction Type: NONE] [Scalar: 0]
; CHECK-NEXT: [p] -> { Stmt_loop[i0] -> MemRef_A[0] };
; CHECK-NEXT: }