Generalize ScalarEvolution to be able to analyze GEPs when
TargetData is not present. It still uses TargetData when available.
This generalization also fixed some limitations in the TargetData
case; the attached testcase covers this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79344 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp
index 3ec6fe4..999fd55 100644
--- a/lib/Analysis/ScalarEvolutionExpander.cpp
+++ b/lib/Analysis/ScalarEvolutionExpander.cpp
@@ -158,53 +158,93 @@
/// check to see if the divide was folded.
static bool FactorOutConstant(const SCEV *&S,
const SCEV *&Remainder,
- const APInt &Factor,
- ScalarEvolution &SE) {
+ const SCEV *Factor,
+ ScalarEvolution &SE,
+ const TargetData *TD) {
// Everything is divisible by one.
- if (Factor == 1)
+ if (Factor->isOne())
return true;
+ // x/x == 1.
+ if (S == Factor) {
+ S = SE.getIntegerSCEV(1, S->getType());
+ return true;
+ }
+
// For a Constant, check for a multiple of the given factor.
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
- ConstantInt *CI =
- ConstantInt::get(SE.getContext(), C->getValue()->getValue().sdiv(Factor));
- // If the quotient is zero and the remainder is non-zero, reject
- // the value at this scale. It will be considered for subsequent
- // smaller scales.
- if (C->isZero() || !CI->isZero()) {
- const SCEV *Div = SE.getConstant(CI);
- S = Div;
- Remainder =
- SE.getAddExpr(Remainder,
- SE.getConstant(C->getValue()->getValue().srem(Factor)));
+ // 0/x == 0.
+ if (C->isZero())
return true;
+ // Check for divisibility.
+ if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) {
+ ConstantInt *CI =
+ ConstantInt::get(SE.getContext(),
+ C->getValue()->getValue().sdiv(
+ FC->getValue()->getValue()));
+ // If the quotient is zero and the remainder is non-zero, reject
+ // the value at this scale. It will be considered for subsequent
+ // smaller scales.
+ if (!CI->isZero()) {
+ const SCEV *Div = SE.getConstant(CI);
+ S = Div;
+ Remainder =
+ SE.getAddExpr(Remainder,
+ SE.getConstant(C->getValue()->getValue().srem(
+ FC->getValue()->getValue())));
+ return true;
+ }
}
}
// In a Mul, check if there is a constant operand which is a multiple
// of the given factor.
- if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S))
- if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
- if (!C->getValue()->getValue().srem(Factor)) {
- const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands();
- SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(),
- MOperands.end());
- NewMulOps[0] =
- SE.getConstant(C->getValue()->getValue().sdiv(Factor));
- S = SE.getMulExpr(NewMulOps);
- return true;
+ if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
+ if (TD) {
+ // With TargetData, the size is known. Check if there is a constant
+ // operand which is a multiple of the given factor. If so, we can
+ // factor it.
+ const SCEVConstant *FC = cast<SCEVConstant>(Factor);
+ if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
+ if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) {
+ const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands();
+ SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(),
+ MOperands.end());
+ NewMulOps[0] =
+ SE.getConstant(C->getValue()->getValue().sdiv(
+ FC->getValue()->getValue()));
+ S = SE.getMulExpr(NewMulOps);
+ return true;
+ }
+ } else {
+ // Without TargetData, check if Factor can be factored out of any of the
+ // Mul's operands. If so, we can just remove it.
+ for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
+ const SCEV *SOp = M->getOperand(i);
+ const SCEV *Remainder = SE.getIntegerSCEV(0, SOp->getType());
+ if (FactorOutConstant(SOp, Remainder, Factor, SE, TD) &&
+ Remainder->isZero()) {
+ const SmallVectorImpl<const SCEV *> &MOperands = M->getOperands();
+ SmallVector<const SCEV *, 4> NewMulOps(MOperands.begin(),
+ MOperands.end());
+ NewMulOps[i] = SOp;
+ S = SE.getMulExpr(NewMulOps);
+ return true;
+ }
}
+ }
+ }
// In an AddRec, check if both start and step are divisible.
if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
const SCEV *Step = A->getStepRecurrence(SE);
const SCEV *StepRem = SE.getIntegerSCEV(0, Step->getType());
- if (!FactorOutConstant(Step, StepRem, Factor, SE))
+ if (!FactorOutConstant(Step, StepRem, Factor, SE, TD))
return false;
if (!StepRem->isZero())
return false;
const SCEV *Start = A->getStart();
- if (!FactorOutConstant(Start, Remainder, Factor, SE))
+ if (!FactorOutConstant(Start, Remainder, Factor, SE, TD))
return false;
S = SE.getAddRecExpr(Start, Step, A->getLoop());
return true;
@@ -213,9 +253,73 @@
return false;
}
+/// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs
+/// is the number of SCEVAddRecExprs present, which are kept at the end of
+/// the list.
+///
+static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops,
+ const Type *Ty,
+ ScalarEvolution &SE) {
+ unsigned NumAddRecs = 0;
+ for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i)
+ ++NumAddRecs;
+ // Group Ops into non-addrecs and addrecs.
+ SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs);
+ SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end());
+ // Let ScalarEvolution sort and simplify the non-addrecs list.
+ const SCEV *Sum = NoAddRecs.empty() ?
+ SE.getIntegerSCEV(0, Ty) :
+ SE.getAddExpr(NoAddRecs);
+ // If it returned an add, use the operands. Otherwise it simplified
+ // the sum into a single value, so just use that.
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum))
+ Ops = Add->getOperands();
+ else {
+ Ops.clear();
+ if (!Sum->isZero())
+ Ops.push_back(Sum);
+ }
+ // Then append the addrecs.
+ Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end());
+}
+
+/// SplitAddRecs - Flatten a list of add operands, moving addrec start values
+/// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}.
+/// This helps expose more opportunities for folding parts of the expressions
+/// into GEP indices.
+///
+static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops,
+ const Type *Ty,
+ ScalarEvolution &SE) {
+ // Find the addrecs.
+ SmallVector<const SCEV *, 8> AddRecs;
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i)
+ while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) {
+ const SCEV *Start = A->getStart();
+ if (Start->isZero()) break;
+ const SCEV *Zero = SE.getIntegerSCEV(0, Ty);
+ AddRecs.push_back(SE.getAddRecExpr(Zero,
+ A->getStepRecurrence(SE),
+ A->getLoop()));
+ if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
+ Ops[i] = Zero;
+ Ops.insert(Ops.end(), Add->op_begin(), Add->op_end());
+ e += Add->getNumOperands();
+ } else {
+ Ops[i] = Start;
+ }
+ }
+ if (!AddRecs.empty()) {
+ // Add the addrecs onto the end of the list.
+ Ops.insert(Ops.end(), AddRecs.begin(), AddRecs.end());
+ // Resort the operand list, moving any constants to the front.
+ SimplifyAddOperands(Ops, Ty, SE);
+ }
+}
+
/// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
/// instead of using ptrtoint+arithmetic+inttoptr. This helps
-/// BasicAliasAnalysis analyze the result.
+/// BasicAliasAnalysis and other passes analyze the result.
///
/// Design note: This depends on ScalarEvolution not recognizing inttoptr
/// and ptrtoint operators, as they may introduce pointer arithmetic
@@ -246,52 +350,62 @@
SmallVector<const SCEV *, 8> Ops(op_begin, op_end);
bool AnyNonZeroIndices = false;
+ // Split AddRecs up into parts as either of the parts may be usable
+ // without the other.
+ SplitAddRecs(Ops, Ty, SE);
+
// Decend down the pointer's type and attempt to convert the other
// operands into GEP indices, at each level. The first index in a GEP
// indexes into the array implied by the pointer operand; the rest of
// the indices index into the element or field type selected by the
// preceding index.
for (;;) {
- APInt ElSize = APInt(SE.getTypeSizeInBits(Ty),
- ElTy->isSized() ? SE.TD->getTypeAllocSize(ElTy) : 0);
- SmallVector<const SCEV *, 8> NewOps;
+ const SCEV *ElSize = SE.getAllocSizeExpr(ElTy);
+ // If the scale size is not 0, attempt to factor out a scale for
+ // array indexing.
SmallVector<const SCEV *, 8> ScaledOps;
- for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
- // Split AddRecs up into parts as either of the parts may be usable
- // without the other.
- if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i]))
- if (!A->getStart()->isZero()) {
- const SCEV *Start = A->getStart();
- Ops.push_back(SE.getAddRecExpr(SE.getIntegerSCEV(0, A->getType()),
- A->getStepRecurrence(SE),
- A->getLoop()));
- Ops[i] = Start;
- ++e;
- }
- // If the scale size is not 0, attempt to factor out a scale.
- if (ElSize != 0) {
+ if (ElTy->isSized() && !ElSize->isZero()) {
+ SmallVector<const SCEV *, 8> NewOps;
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
const SCEV *Op = Ops[i];
- const SCEV *Remainder = SE.getIntegerSCEV(0, Op->getType());
- if (FactorOutConstant(Op, Remainder, ElSize, SE)) {
- ScaledOps.push_back(Op); // Op now has ElSize factored out.
- NewOps.push_back(Remainder);
- continue;
+ const SCEV *Remainder = SE.getIntegerSCEV(0, Ty);
+ if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.TD)) {
+ // Op now has ElSize factored out.
+ ScaledOps.push_back(Op);
+ if (!Remainder->isZero())
+ NewOps.push_back(Remainder);
+ AnyNonZeroIndices = true;
+ } else {
+ // The operand was not divisible, so add it to the list of operands
+ // we'll scan next iteration.
+ NewOps.push_back(Ops[i]);
}
}
- // If the operand was not divisible, add it to the list of operands
- // we'll scan next iteration.
- NewOps.push_back(Ops[i]);
+ // If we made any changes, update Ops.
+ if (!ScaledOps.empty()) {
+ Ops = NewOps;
+ SimplifyAddOperands(Ops, Ty, SE);
+ }
}
- Ops = NewOps;
- AnyNonZeroIndices |= !ScaledOps.empty();
+
+ // Record the scaled array index for this level of the type. If
+ // we didn't find any operands that could be factored, tentatively
+ // assume that element zero was selected (since the zero offset
+ // would obviously be folded away).
Value *Scaled = ScaledOps.empty() ?
Constant::getNullValue(Ty) :
expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
GepIndices.push_back(Scaled);
// Collect struct field index operands.
- if (!Ops.empty())
- while (const StructType *STy = dyn_cast<StructType>(ElTy)) {
+ while (const StructType *STy = dyn_cast<StructType>(ElTy)) {
+ bool FoundFieldNo = false;
+ // An empty struct has no fields.
+ if (STy->getNumElements() == 0) break;
+ if (SE.TD) {
+ // With TargetData, field offsets are known. See if a constant offset
+ // falls within any of the struct fields.
+ if (Ops.empty()) break;
if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
if (SE.getTypeSizeInBits(C->getType()) <= 64) {
const StructLayout &SL = *SE.TD->getStructLayout(STy);
@@ -304,25 +418,52 @@
Ops[0] =
SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx));
AnyNonZeroIndices = true;
- continue;
+ FoundFieldNo = true;
}
}
- break;
+ } else {
+ // Without TargetData, just check for a SCEVFieldOffsetExpr of the
+ // appropriate struct type.
+ for (unsigned i = 0, e = Ops.size(); i != e; ++i)
+ if (const SCEVFieldOffsetExpr *FO =
+ dyn_cast<SCEVFieldOffsetExpr>(Ops[i]))
+ if (FO->getStructType() == STy) {
+ unsigned FieldNo = FO->getFieldNo();
+ GepIndices.push_back(
+ ConstantInt::get(Type::getInt32Ty(Ty->getContext()),
+ FieldNo));
+ ElTy = STy->getTypeAtIndex(FieldNo);
+ Ops[i] = SE.getConstant(Ty, 0);
+ AnyNonZeroIndices = true;
+ FoundFieldNo = true;
+ break;
+ }
}
-
- if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy)) {
- ElTy = ATy->getElementType();
- continue;
+ // If no struct field offsets were found, tentatively assume that
+ // field zero was selected (since the zero offset would obviously
+ // be folded away).
+ if (!FoundFieldNo) {
+ ElTy = STy->getTypeAtIndex(0u);
+ GepIndices.push_back(
+ Constant::getNullValue(Type::getInt32Ty(Ty->getContext())));
+ }
}
- break;
+
+ if (const ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
+ ElTy = ATy->getElementType();
+ else
+ break;
}
// If none of the operands were convertable to proper GEP indices, cast
// the base to i8* and do an ugly getelementptr with that. It's still
// better than ptrtoint+arithmetic+inttoptr at least.
if (!AnyNonZeroIndices) {
+ // Cast the base to i8*.
V = InsertNoopCastOfTo(V,
Type::getInt8Ty(Ty->getContext())->getPointerTo(PTy->getAddressSpace()));
+
+ // Expand the operands for a plain byte offset.
Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
// Fold a GEP with constant operands.
@@ -345,7 +486,8 @@
}
}
- Value *GEP = Builder.CreateGEP(V, Idx, "scevgep");
+ // Emit a GEP.
+ Value *GEP = Builder.CreateGEP(V, Idx, "uglygep");
InsertedValues.insert(GEP);
return GEP;
}
@@ -368,11 +510,10 @@
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
- if (SE.TD)
- if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
- const SmallVectorImpl<const SCEV *> &Ops = S->getOperands();
- return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1], PTy, Ty, V);
- }
+ if (const PointerType *PTy = dyn_cast<PointerType>(V->getType())) {
+ const SmallVectorImpl<const SCEV *> &Ops = S->getOperands();
+ return expandAddToGEP(&Ops[0], &Ops[Ops.size() - 1], PTy, Ty, V);
+ }
V = InsertNoopCastOfTo(V, Ty);
@@ -484,21 +625,19 @@
// Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
// comments on expandAddToGEP for details.
- if (SE.TD) {
- const SCEV *Base = S->getStart();
- const SCEV *RestArray[1] = { Rest };
- // Dig into the expression to find the pointer base for a GEP.
- ExposePointerBase(Base, RestArray[0], SE);
- // If we found a pointer, expand the AddRec with a GEP.
- if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
- // Make sure the Base isn't something exotic, such as a multiplied
- // or divided pointer value. In those cases, the result type isn't
- // actually a pointer type.
- if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
- Value *StartV = expand(Base);
- assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
- return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
- }
+ const SCEV *Base = S->getStart();
+ const SCEV *RestArray[1] = { Rest };
+ // Dig into the expression to find the pointer base for a GEP.
+ ExposePointerBase(Base, RestArray[0], SE);
+ // If we found a pointer, expand the AddRec with a GEP.
+ if (const PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
+ // Make sure the Base isn't something exotic, such as a multiplied
+ // or divided pointer value. In those cases, the result type isn't
+ // actually a pointer type.
+ if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
+ Value *StartV = expand(Base);
+ assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
+ return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
}
}
@@ -656,6 +795,14 @@
return LHS;
}
+Value *SCEVExpander::visitFieldOffsetExpr(const SCEVFieldOffsetExpr *S) {
+ return ConstantExpr::getOffsetOf(S->getStructType(), S->getFieldNo());
+}
+
+Value *SCEVExpander::visitAllocSizeExpr(const SCEVAllocSizeExpr *S) {
+ return ConstantExpr::getSizeOf(S->getAllocType());
+}
+
Value *SCEVExpander::expandCodeFor(const SCEV *SH, const Type *Ty) {
// Expand the code for this SCEV.
Value *V = expand(SH);