/// canExpandBackedgeTakenCount - Return true if this loop's backedge taken
/// count expression can be safely and cheaply expanded into an instruction
/// sequence that can be used by LinearFunctionTestReplace.
+///
+/// TODO: This fails for pointer-type loop counters with greater than one byte
+/// strides, consequently preventing LFTR from running. For the purpose of LFTR
+/// we could skip this check in the case that the LFTR loop counter (chosen by
+/// FindLoopCounter) is also pointer type. Instead, we could directly convert
+/// the loop test to an inequality test by checking the target data's alignment
+/// of element types (given that the initial pointer value originates from or is
+/// used by ABI constrained operation, as opposed to inttoptr/ptrtoint).
+/// However, we don't yet have a strong motivation for converting loop tests
+/// into inequality tests.
static bool canExpandBackedgeTakenCount(Loop *L, ScalarEvolution *SE) {
const SCEV *BackedgeTakenCount = SE->getBackedgeTakenCount(L);
if (isa<SCEVCouldNotCompute>(BackedgeTakenCount) ||
/// FindLoopCounter - Find an affine IV in canonical form.
///
+/// BECount may be an i8* pointer type. The pointer difference is already
+/// valid count without scaling the address stride, so it remains a pointer
+/// expression as far as SCEV is concerned.
+///
/// FIXME: Accept -1 stride and set IVLimit = IVInit - BECount
///
/// FIXME: Accept non-unit stride as long as SCEV can reduce BECount * Stride.
static PHINode *
FindLoopCounter(Loop *L, const SCEV *BECount,
ScalarEvolution *SE, DominatorTree *DT, const TargetData *TD) {
- // I'm not sure how BECount could be a pointer type, but we definitely don't
- // want to LFTR that.
- if (BECount->getType()->isPointerTy())
- return 0;
-
uint64_t BCWidth = SE->getTypeSizeInBits(BECount->getType());
Value *Cond =
if (!SE->isSCEVable(Phi->getType()))
continue;
+ // Avoid comparing an integer IV against a pointer Limit.
+ if (BECount->getType()->isPointerTy() && !Phi->getType()->isPointerTy())
+ continue;
+
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(Phi));
if (!AR || AR->getLoop() != L || !AR->isAffine())
continue;
return BestPhi;
}
+/// genLoopLimit - Help LinearFunctionTestReplace by generating a value that
+/// holds the RHS of the new loop test.
+static Value *genLoopLimit(PHINode *IndVar, const SCEV *IVCount, Loop *L,
+ SCEVExpander &Rewriter, ScalarEvolution *SE) {
+ const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(IndVar));
+ assert(AR && AR->getLoop() == L && AR->isAffine() && "bad loop counter");
+ const SCEV *IVInit = AR->getStart();
+
+ // IVInit may be a pointer while IVCount is an integer when FindLoopCounter
+ // finds a valid pointer IV. Sign extend BECount in order to materialize a
+ // GEP. Avoid running SCEVExpander on a new pointer value, instead reusing
+ // the existing GEPs whenever possible.
+ if (IndVar->getType()->isPointerTy()
+ && !IVCount->getType()->isPointerTy()) {
+
+ Type *OfsTy = SE->getEffectiveSCEVType(IVInit->getType());
+ const SCEV *IVOffset = SE->getTruncateOrSignExtend(IVCount, OfsTy);
+
+ // Expand the code for the iteration count.
+ assert(SE->isLoopInvariant(IVOffset, L) &&
+ "Computed iteration count is not loop invariant!");
+ BranchInst *BI = cast<BranchInst>(L->getExitingBlock()->getTerminator());
+ Value *GEPOffset = Rewriter.expandCodeFor(IVOffset, OfsTy, BI);
+
+ Value *GEPBase = IndVar->getIncomingValueForBlock(L->getLoopPreheader());
+ assert(AR->getStart() == SE->getSCEV(GEPBase) && "bad loop counter");
+ // We could handle pointer IVs other than i8*, but we need to compensate for
+ // gep index scaling. See canExpandBackedgeTakenCount comments.
+ assert(SE->getSizeOfExpr(
+ cast<PointerType>(GEPBase->getType())->getElementType())->isOne()
+ && "unit stride pointer IV must be i8*");
+
+ IRBuilder<> Builder(L->getLoopPreheader()->getTerminator());
+ return Builder.CreateGEP(GEPBase, GEPOffset, "lftr.limit");
+ }
+ else {
+ // In any other case, convert both IVInit and IVCount to integers before
+ // comparing. This may result in SCEV expension of pointers, but in practice
+ // SCEV will fold the pointer arithmetic away as such:
+ // BECount = (IVEnd - IVInit - 1) => IVLimit = IVInit (postinc).
+ //
+ // Valid Cases: (1) both integers is most common; (2) both may be pointers
+ // for simple memset-style loops; (3) IVInit is an integer and IVCount is a
+ // pointer may occur when enable-iv-rewrite generates a canonical IV on top
+ // of case #2.
+
+ const SCEV *IVLimit = 0;
+ // For unit stride, IVCount = Start + BECount with 2's complement overflow.
+ // For non-zero Start, compute IVCount here.
+ if (AR->getStart()->isZero())
+ IVLimit = IVCount;
+ else {
+ assert(AR->getStepRecurrence(*SE)->isOne() && "only handles unit stride");
+ const SCEV *IVInit = AR->getStart();
+
+ // For integer IVs, truncate the IV before computing IVInit + BECount.
+ if (SE->getTypeSizeInBits(IVInit->getType())
+ > SE->getTypeSizeInBits(IVCount->getType()))
+ IVInit = SE->getTruncateExpr(IVInit, IVCount->getType());
+
+ IVLimit = SE->getAddExpr(IVInit, IVCount);
+ }
+ // Expand the code for the iteration count.
+ BranchInst *BI = cast<BranchInst>(L->getExitingBlock()->getTerminator());
+ IRBuilder<> Builder(BI);
+ assert(SE->isLoopInvariant(IVLimit, L) &&
+ "Computed iteration count is not loop invariant!");
+ // Ensure that we generate the same type as IndVar, or a smaller integer
+ // type. In the presence of null pointer values, we have an integer type
+ // SCEV expression (IVInit) for a pointer type IV value (IndVar).
+ Type *LimitTy = IVCount->getType()->isPointerTy() ?
+ IndVar->getType() : IVCount->getType();
+ return Rewriter.expandCodeFor(IVLimit, LimitTy, BI);
+ }
+}
+
/// LinearFunctionTestReplace - This method rewrites the exit condition of the
/// loop to be a canonical != comparison against the incremented loop induction
/// variable. This pass is able to rewrite the exit tests of any loop where the
PHINode *IndVar,
SCEVExpander &Rewriter) {
assert(canExpandBackedgeTakenCount(L, SE) && "precondition");
- BranchInst *BI = cast<BranchInst>(L->getExitingBlock()->getTerminator());
// LFTR can ignore IV overflow and truncate to the width of
// BECount. This avoids materializing the add(zext(add)) expression.
Type *CntTy = !EnableIVRewrite ?
BackedgeTakenCount->getType() : IndVar->getType();
- const SCEV *IVLimit = BackedgeTakenCount;
+ const SCEV *IVCount = BackedgeTakenCount;
- // If the exiting block is not the same as the backedge block, we must compare
- // against the preincremented value, otherwise we prefer to compare against
- // the post-incremented value.
+ // If the exiting block is the same as the backedge block, we prefer to
+ // compare against the post-incremented value, otherwise we must compare
+ // against the preincremented value.
Value *CmpIndVar;
if (L->getExitingBlock() == L->getLoopLatch()) {
// Add one to the "backedge-taken" count to get the trip count.
// If this addition may overflow, we have to be more pessimistic and
// cast the induction variable before doing the add.
const SCEV *N =
- SE->getAddExpr(IVLimit, SE->getConstant(IVLimit->getType(), 1));
- if (CntTy == IVLimit->getType())
- IVLimit = N;
+ SE->getAddExpr(IVCount, SE->getConstant(IVCount->getType(), 1));
+ if (CntTy == IVCount->getType())
+ IVCount = N;
else {
- const SCEV *Zero = SE->getConstant(IVLimit->getType(), 0);
+ const SCEV *Zero = SE->getConstant(IVCount->getType(), 0);
if ((isa<SCEVConstant>(N) && !N->isZero()) ||
SE->isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, N, Zero)) {
// No overflow. Cast the sum.
- IVLimit = SE->getTruncateOrZeroExtend(N, CntTy);
+ IVCount = SE->getTruncateOrZeroExtend(N, CntTy);
} else {
// Potential overflow. Cast before doing the add.
- IVLimit = SE->getTruncateOrZeroExtend(IVLimit, CntTy);
- IVLimit = SE->getAddExpr(IVLimit, SE->getConstant(CntTy, 1));
+ IVCount = SE->getTruncateOrZeroExtend(IVCount, CntTy);
+ IVCount = SE->getAddExpr(IVCount, SE->getConstant(CntTy, 1));
}
}
// The BackedgeTaken expression contains the number of times that the
// number of times the loop executes, so use the incremented indvar.
CmpIndVar = IndVar->getIncomingValueForBlock(L->getExitingBlock());
} else {
- // We have to use the preincremented value...
- IVLimit = SE->getTruncateOrZeroExtend(IVLimit, CntTy);
+ // We must use the preincremented value...
+ IVCount = SE->getTruncateOrZeroExtend(IVCount, CntTy);
CmpIndVar = IndVar;
}
- // For unit stride, IVLimit = Start + BECount with 2's complement overflow.
- // So for non-zero start compute the IVLimit here.
- Type *CmpTy = CntTy;
- const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(IndVar));
- assert(AR && AR->getLoop() == L && AR->isAffine() && "bad loop counter");
- if (!AR->getStart()->isZero()) {
- assert(AR->getStepRecurrence(*SE)->isOne() && "only handles unit stride");
- const SCEV *IVInit = AR->getStart();
-
- // For pointer types, sign extend BECount in order to materialize a GEP.
- // Note that for without EnableIVRewrite, we never run SCEVExpander on a
- // pointer type, because we must preserve the existing GEPs. Instead we
- // directly generate a GEP later.
- if (CmpIndVar->getType()->isPointerTy()) {
- CmpTy = SE->getEffectiveSCEVType(IVInit->getType());
- IVLimit = SE->getTruncateOrSignExtend(IVLimit, CmpTy);
- }
- // For integer types, truncate the IV before computing IVInit + BECount.
- else {
- if (SE->getTypeSizeInBits(IVInit->getType())
- > SE->getTypeSizeInBits(CmpTy))
- IVInit = SE->getTruncateExpr(IVInit, CmpTy);
-
- IVLimit = SE->getAddExpr(IVInit, IVLimit);
- }
- }
- // Expand the code for the iteration count.
- IRBuilder<> Builder(BI);
-
- assert(SE->isLoopInvariant(IVLimit, L) &&
- "Computed iteration count is not loop invariant!");
- assert((EnableIVRewrite || !IVLimit->getType()->isPointerTy()) &&
- "Should not expand pointer types" );
- Value *ExitCnt = Rewriter.expandCodeFor(IVLimit, CmpTy, BI);
-
- // Create a gep for IVInit + IVLimit from on an existing pointer base.
- //
- // In the presence of null pointer values, the SCEV expression may be an
- // integer type while the IV is a pointer type. Ensure that the compare
- // operands are always the same type by checking the IV type here.
- if (CmpIndVar->getType()->isPointerTy()) {
- Value *IVStart = IndVar->getIncomingValueForBlock(L->getLoopPreheader());
- assert(AR->getStart() == SE->getSCEV(IVStart) && "bad loop counter");
- assert(SE->getSizeOfExpr(
- cast<PointerType>(IVStart->getType())->getElementType())->isOne()
- && "unit stride pointer IV must be i8*");
-
- Builder.SetInsertPoint(L->getLoopPreheader()->getTerminator());
- ExitCnt = Builder.CreateGEP(IVStart, ExitCnt, "lftr.limit");
- Builder.SetInsertPoint(BI);
- }
+ Value *ExitCnt = genLoopLimit(IndVar, IVCount, L, Rewriter, SE);
+ assert(ExitCnt->getType()->isPointerTy() == IndVar->getType()->isPointerTy()
+ && "genLoopLimit missed a cast");
// Insert a new icmp_ne or icmp_eq instruction before the branch.
+ BranchInst *BI = cast<BranchInst>(L->getExitingBlock()->getTerminator());
ICmpInst::Predicate P;
if (L->contains(BI->getSuccessor(0)))
P = ICmpInst::ICMP_NE;
<< " op:\t"
<< (P == ICmpInst::ICMP_NE ? "!=" : "==") << "\n"
<< " RHS:\t" << *ExitCnt << "\n"
- << " Expr:\t" << *IVLimit << "\n");
+ << " IVCount:\t" << *IVCount << "\n");
+ IRBuilder<> Builder(BI);
if (SE->getTypeSizeInBits(CmpIndVar->getType())
- > SE->getTypeSizeInBits(CmpTy)) {
- CmpIndVar = Builder.CreateTrunc(CmpIndVar, CmpTy, "lftr.wideiv");
+ > SE->getTypeSizeInBits(ExitCnt->getType())) {
+ CmpIndVar = Builder.CreateTrunc(CmpIndVar, ExitCnt->getType(),
+ "lftr.wideiv");
}
Value *Cond = Builder.CreateICmp(P, CmpIndVar, ExitCnt, "exitcond");
-; RUN: opt < %s -indvars -S -enable-iv-rewrite=true | FileCheck %s
+; RUN: opt < %s -indvars -S -enable-iv-rewrite=false "-default-data-layout=e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64" | FileCheck %s
+; RUN: opt < %s -indvars -S -enable-iv-rewrite=true "-default-data-layout=e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64" | FileCheck %s
+; RUN: opt < %s -indvars -S -enable-iv-rewrite=false "-default-data-layout=e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32" | FileCheck %s
+; RUN: opt < %s -indvars -S -enable-iv-rewrite=true "-default-data-layout=e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32" | FileCheck %s
;
; PR11279: Assertion !IVLimit->getType()->isPointerTy()
;
-; Test a non-integer BECount. It doesn't make sense, but that's what
-; falls out of SCEV. Since it's an i8*, we never adjust in a way that
-; would convert it to an integer type.
-;
-; enable-iv-rewrite=false does not currently perform LFTR when the the
-; taken count is a pointer expression, but that will change son.
+; Test LinearFunctionTestReplace of a pointer-type loop counter. Note
+; that BECount may or may not be a pointer type. A pointer type
+; BECount doesn't really make sense, but that's what falls out of
+; SCEV. Since it's an i8*, it has unit stride so we never adjust the
+; SCEV expression in a way that would convert it to an integer type.
+
+; CHECK: @testnullptrptr
+; CHECK: loop:
+; CHECK: icmp ne
+define i8 @testnullptrptr(i8* %buf, i8* %end) nounwind {
+ br label %loopguard
+
+loopguard:
+ %guard = icmp ult i8* null, %end
+ br i1 %guard, label %preheader, label %exit
+
+preheader:
+ br label %loop
+
+loop:
+ %p.01.us.us = phi i8* [ null, %preheader ], [ %gep, %loop ]
+ %s = phi i8 [0, %preheader], [%snext, %loop]
+ %gep = getelementptr inbounds i8* %p.01.us.us, i64 1
+ %snext = load i8* %gep
+ %cmp = icmp ult i8* %gep, %end
+ br i1 %cmp, label %loop, label %exit
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
-target triple = "x86_64-apple-darwin"
+exit:
+ ret i8 %snext
+}
-; CHECK: @test8
+; CHECK: @testptrptr
; CHECK: loop:
; CHECK: icmp ne
-define i8 @test8(i8* %buf, i8* %end) nounwind {
+define i8 @testptrptr(i8* %buf, i8* %end) nounwind {
br label %loopguard
loopguard:
exit:
ret i8 %snext
}
+
+; CHECK: @testnullptrint
+; CHECK: loop:
+; CHECK: icmp ne
+define i8 @testnullptrint(i8* %buf, i8* %end) nounwind {
+ br label %loopguard
+
+loopguard:
+ %bi = ptrtoint i8* %buf to i32
+ %ei = ptrtoint i8* %end to i32
+ %cnt = sub i32 %ei, %bi
+ %guard = icmp ult i32 0, %cnt
+ br i1 %guard, label %preheader, label %exit
+
+preheader:
+ br label %loop
+
+loop:
+ %p.01.us.us = phi i8* [ null, %preheader ], [ %gep, %loop ]
+ %iv = phi i32 [ 0, %preheader ], [ %ivnext, %loop ]
+ %s = phi i8 [0, %preheader], [%snext, %loop]
+ %gep = getelementptr inbounds i8* %p.01.us.us, i64 1
+ %snext = load i8* %gep
+ %ivnext = add i32 %iv, 1
+ %cmp = icmp ult i32 %ivnext, %cnt
+ br i1 %cmp, label %loop, label %exit
+
+exit:
+ ret i8 %snext
+}
+
+; CHECK: @testptrint
+; CHECK: loop:
+; CHECK: icmp ne
+define i8 @testptrint(i8* %buf, i8* %end) nounwind {
+ br label %loopguard
+
+loopguard:
+ %bi = ptrtoint i8* %buf to i32
+ %ei = ptrtoint i8* %end to i32
+ %cnt = sub i32 %ei, %bi
+ %guard = icmp ult i32 %bi, %cnt
+ br i1 %guard, label %preheader, label %exit
+
+preheader:
+ br label %loop
+
+loop:
+ %p.01.us.us = phi i8* [ %buf, %preheader ], [ %gep, %loop ]
+ %iv = phi i32 [ %bi, %preheader ], [ %ivnext, %loop ]
+ %s = phi i8 [0, %preheader], [%snext, %loop]
+ %gep = getelementptr inbounds i8* %p.01.us.us, i64 1
+ %snext = load i8* %gep
+ %ivnext = add i32 %iv, 1
+ %cmp = icmp ult i32 %ivnext, %cnt
+ br i1 %cmp, label %loop, label %exit
+
+exit:
+ ret i8 %snext
+}
+
+; IV and BECount have two different pointer types here.
+define void @testnullptr([512 x i8]* %base) nounwind {
+entry:
+ %add.ptr1603 = getelementptr [512 x i8]* %base, i64 0, i64 512
+ br label %preheader
+
+preheader:
+ %cmp1604192 = icmp ult i8* undef, %add.ptr1603
+ br i1 %cmp1604192, label %for.body, label %for.end1609
+
+for.body:
+ %r.17193 = phi i8* [ %incdec.ptr1608, %for.body ], [ null, %preheader ]
+ %incdec.ptr1608 = getelementptr i8* %r.17193, i64 1
+ %cmp1604 = icmp ult i8* %incdec.ptr1608, %add.ptr1603
+ br i1 %cmp1604, label %for.body, label %for.end1609
+
+for.end1609:
+ unreachable
+}
projects / oota-llvm.git / commitdiff