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[FIX] Approximate non-affine loops correctly 

Before isValidCFG() could hide the fact that a loop is non-affine by
  over-approximation. This is problematic if a subregion of the loop contains
  an exit/latch block and is over-approximated. Now we do not over-approximate
  in the isValidCFG function if we check loop control.  If such control is
  non-affine the whole loop is over-approximated, not only a subregion.

llvm-svn: 249273
This commit is contained in:
Johannes Doerfert 2015-10-04 14:54:27 +00:00
parent 30ffb6fcb6
commit 757a32b5b3
3 changed files with 114 additions and 61 deletions
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30
polly/include/polly/ScopDetection.h
View File

@ -281,33 +281,37 @@ private:
/// @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.
/// @param BB The block to check.
/// @param SI The switch to check.
/// @param Condition The switch condition.
/// @param IsLoopBranch Flag to indicate the branch is a loop exit/latch.
/// @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;
bool IsLoopBranch, 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.
/// @param BB The block to check.
/// @param BI The branch to check.
/// @param Condition The branch condition.
/// @param IsLoopBranch Flag to indicate the branch is a loop exit/latch.
/// @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;
bool IsLoopBranch, DetectionContext &Context) const;
/// @brief Check if the control flow in a basic block is valid.
///
/// @param BB The BB to check the control flow.
/// @param Context The context of scop detection.
/// @param BB The BB to check the control flow.
/// @param IsLoopBranch Flag to indicate the branch is a loop exit/latch.
/// @param Context The context of scop detection.
///
/// @return True if the BB contains only valid control flow.
bool isValidCFG(BasicBlock &BB, DetectionContext &Context) const;
bool isValidCFG(BasicBlock &BB, bool IsLoopBranch,
DetectionContext &Context) const;
/// @brief Is a loop valid with respect to a given region.
///

106
polly/lib/Analysis/ScopDetection.cpp
View File

@ -300,71 +300,79 @@ bool ScopDetection::addOverApproximatedRegion(Region *AR,
}
bool ScopDetection::isValidSwitch(BasicBlock &BB, SwitchInst *SI,
Value *Condition,
Value *Condition, bool IsLoopBranch,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;
Loop *L = LI->getLoopFor(&BB);
const SCEV *ConditionSCEV = SE->getSCEVAtScope(Condition, L);
if (!isAffineExpr(&CurRegion, ConditionSCEV, *SE))
if (!AllowNonAffineSubRegions ||
!addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return invalid<ReportNonAffBranch>(Context, /*Assert=*/true, &BB,
ConditionSCEV, ConditionSCEV, SI);
if (isAffineExpr(&CurRegion, ConditionSCEV, *SE))
return true;
return true;
if (!IsLoopBranch && AllowNonAffineSubRegions &&
addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return true;
if (IsLoopBranch)
return false;
return invalid<ReportNonAffBranch>(Context, /*Assert=*/true, &BB,
ConditionSCEV, ConditionSCEV, SI);
}
bool ScopDetection::isValidBranch(BasicBlock &BB, BranchInst *BI,
Value *Condition,
Value *Condition, bool IsLoopBranch,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;
// 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, BI, &BB);
if (!IsLoopBranch && AllowNonAffineSubRegions &&
addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return true;
return invalid<ReportInvalidCond>(Context, /*Assert=*/true, BI, &BB);
}
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, BI, &BB);
ICmpInst *ICmp = 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, BI, &BB);
// Are both operands of the ICmp affine?
if (isa<UndefValue>(ICmp->getOperand(0)) ||
isa<UndefValue>(ICmp->getOperand(1)))
return invalid<ReportUndefOperand>(Context, /*Assert=*/true, &BB, ICmp);
// Are both operands of the ICmp affine?
if (isa<UndefValue>(ICmp->getOperand(0)) ||
isa<UndefValue>(ICmp->getOperand(1)))
return invalid<ReportUndefOperand>(Context, /*Assert=*/true, &BB, ICmp);
// TODO: FIXME: IslExprBuilder is not capable of producing valid code
// for arbitrary pointer expressions at the moment. Until
// this is fixed we disallow pointer expressions completely.
if (ICmp->getOperand(0)->getType()->isPointerTy())
return false;
// TODO: FIXME: IslExprBuilder is not capable of producing valid code
// for arbitrary pointer expressions at the moment. Until
// this is fixed we disallow pointer expressions completely.
if (ICmp->getOperand(0)->getType()->isPointerTy())
return false;
Loop *L = LI->getLoopFor(ICmp->getParent());
const SCEV *LHS = SE->getSCEVAtScope(ICmp->getOperand(0), L);
const SCEV *RHS = SE->getSCEVAtScope(ICmp->getOperand(1), L);
Loop *L = LI->getLoopFor(ICmp->getParent());
const SCEV *LHS = SE->getSCEVAtScope(ICmp->getOperand(0), L);
const SCEV *RHS = SE->getSCEVAtScope(ICmp->getOperand(1), L);
if (!isAffineExpr(&CurRegion, LHS, *SE) ||
!isAffineExpr(&CurRegion, RHS, *SE)) {
if (!AllowNonAffineSubRegions ||
!addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return invalid<ReportNonAffBranch>(Context, /*Assert=*/true, &BB, LHS,
RHS, ICmp);
}
}
if (isAffineExpr(&CurRegion, LHS, *SE) && isAffineExpr(&CurRegion, RHS, *SE))
return true;
return true;
if (!IsLoopBranch && AllowNonAffineSubRegions &&
addOverApproximatedRegion(RI->getRegionFor(&BB), Context))
return true;
if (IsLoopBranch)
return false;
return invalid<ReportNonAffBranch>(Context, /*Assert=*/true, &BB, LHS, RHS,
ICmp);
}
bool ScopDetection::isValidCFG(BasicBlock &BB,
bool ScopDetection::isValidCFG(BasicBlock &BB, bool IsLoopBranch,
DetectionContext &Context) const {
Region &CurRegion = Context.CurRegion;
@ -388,12 +396,12 @@ bool ScopDetection::isValidCFG(BasicBlock &BB,
return true;
if (BranchInst *BI = dyn_cast<BranchInst>(TI))
return isValidBranch(BB, BI, Condition, Context);
return isValidBranch(BB, BI, Condition, IsLoopBranch, Context);
SwitchInst *SI = dyn_cast<SwitchInst>(TI);
assert(SI && "Terminator was neither branch nor switch");
return isValidSwitch(BB, SI, Condition, Context);
return isValidSwitch(BB, SI, Condition, IsLoopBranch, Context);
}
bool ScopDetection::isValidCallInst(CallInst &CI) {
@ -735,7 +743,7 @@ bool ScopDetection::canUseISLTripCount(Loop *L,
L->getLoopLatches(LoopControlBlocks);
L->getExitingBlocks(LoopControlBlocks);
for (BasicBlock *ControlBB : LoopControlBlocks) {
if (!isValidCFG(*ControlBB, Context))
if (!isValidCFG(*ControlBB, true, Context))
return false;
}
@ -751,9 +759,11 @@ bool ScopDetection::isValidLoop(Loop *L, DetectionContext &Context) const {
if (AllowNonAffineSubLoops && AllowNonAffineSubRegions) {
Region *R = RI->getRegionFor(L->getHeader());
if (R->contains(L))
if (addOverApproximatedRegion(R, Context))
return true;
while (R != &Context.CurRegion && !R->contains(L))
R = R->getParent();
if (addOverApproximatedRegion(R, Context))
return true;
}
const SCEV *LoopCount = SE->getBackedgeTakenCount(L);
@ -948,7 +958,7 @@ bool ScopDetection::allBlocksValid(DetectionContext &Context) const {
if (isErrorBlock(*BB))
continue;
if (!isValidCFG(*BB, Context) && !KeepGoing)
if (!isValidCFG(*BB, false, Context) && !KeepGoing)
return false;
for (BasicBlock::iterator I = BB->begin(), E = --BB->end(); I != E; ++I)
if (!isValidInstruction(*I, Context) && !KeepGoing)

39
polly/test/ScopDetect/invalid-latch-conditions.ll Normal file
View File

@ -0,0 +1,39 @@
; RUN: opt %loadPolly -polly-detect -analyze < %s | FileCheck %s
; RUN: opt %loadPolly -polly-allow-nonaffine-loops -polly-detect -analyze < %s | FileCheck %s --check-prefix=NALOOPS
; The latch conditions of the outer loop are not affine, thus the loop cannot
; handled by the domain generation and needs to be overapproximated.
; CHECK-NOT: Valid
; NALOOPS: Valid Region for Scop: for.body.6 => for.end.45
; ModuleID = '/home/johannes/Downloads/bug.ll'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
; Function Attrs: nounwind uwtable
define void @kernel_reg_detect([6 x i32]* %path) #0 {
entry:
br label %for.body.6
for.body.6: ; preds = %for.inc.43, %for.body.6, %entry
%indvars.iv9 = phi i64 [ %indvars.iv.next10, %for.body.6 ], [ 0, %for.inc.43 ], [ 0, %entry ]
%indvars.iv.next10 = add nuw nsw i64 %indvars.iv9, 1
%lftr.wideiv = trunc i64 %indvars.iv.next10 to i32
%exitcond = icmp ne i32 %lftr.wideiv, 6
br i1 %exitcond, label %for.body.6, label %for.inc.40
for.inc.40: ; preds = %for.inc.40, %for.body.6
%arrayidx28 = getelementptr inbounds [6 x i32], [6 x i32]* %path, i64 0, i64 0
%tmp = load i32, i32* %arrayidx28, align 4
%arrayidx36 = getelementptr inbounds [6 x i32], [6 x i32]* %path, i64 0, i64 0
store i32 0, i32* %arrayidx36, align 4
%exitcond22 = icmp ne i64 0, 6
br i1 %exitcond22, label %for.inc.40, label %for.inc.43
for.inc.43: ; preds = %for.inc.40
%exitcond23 = icmp ne i32 0, 10000
br i1 %exitcond23, label %for.body.6, label %for.end.45
for.end.45: ; preds = %for.inc.43
ret void
}