diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index c2be91c783e..1aadac4771a 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -4108,127 +4108,128 @@ const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) { break; } } - if (BEValueV && StartValueV) { - // While we are analyzing this PHI node, handle its value symbolically. - const SCEV *SymbolicName = getUnknown(PN); - assert(ValueExprMap.find_as(PN) == ValueExprMap.end() && - "PHI node already processed?"); - ValueExprMap.insert({SCEVCallbackVH(PN, this), SymbolicName}); + if (!BEValueV || !StartValueV) + return nullptr; - // Using this symbolic name for the PHI, analyze the value coming around - // the back-edge. - const SCEV *BEValue = getSCEV(BEValueV); + // While we are analyzing this PHI node, handle its value symbolically. + const SCEV *SymbolicName = getUnknown(PN); + assert(ValueExprMap.find_as(PN) == ValueExprMap.end() && + "PHI node already processed?"); + ValueExprMap.insert({SCEVCallbackVH(PN, this), SymbolicName}); - // NOTE: If BEValue is loop invariant, we know that the PHI node just - // has a special value for the first iteration of the loop. + // Using this symbolic name for the PHI, analyze the value coming around + // the back-edge. + const SCEV *BEValue = getSCEV(BEValueV); - // If the value coming around the backedge is an add with the symbolic - // value we just inserted, then we found a simple induction variable! - if (const SCEVAddExpr *Add = dyn_cast(BEValue)) { - // If there is a single occurrence of the symbolic value, replace it - // with a recurrence. - unsigned FoundIndex = Add->getNumOperands(); + // NOTE: If BEValue is loop invariant, we know that the PHI node just + // has a special value for the first iteration of the loop. + + // If the value coming around the backedge is an add with the symbolic + // value we just inserted, then we found a simple induction variable! + if (const SCEVAddExpr *Add = dyn_cast(BEValue)) { + // If there is a single occurrence of the symbolic value, replace it + // with a recurrence. + unsigned FoundIndex = Add->getNumOperands(); + for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) + if (Add->getOperand(i) == SymbolicName) + if (FoundIndex == e) { + FoundIndex = i; + break; + } + + if (FoundIndex != Add->getNumOperands()) { + // Create an add with everything but the specified operand. + SmallVector Ops; for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) - if (Add->getOperand(i) == SymbolicName) - if (FoundIndex == e) { - FoundIndex = i; - break; + if (i != FoundIndex) + Ops.push_back(Add->getOperand(i)); + const SCEV *Accum = getAddExpr(Ops); + + // This is not a valid addrec if the step amount is varying each + // loop iteration, but is not itself an addrec in this loop. + if (isLoopInvariant(Accum, L) || + (isa(Accum) && + cast(Accum)->getLoop() == L)) { + SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; + + if (auto BO = MatchBinaryOp(BEValueV, DT)) { + if (BO->Opcode == Instruction::Add && BO->LHS == PN) { + if (BO->IsNUW) + Flags = setFlags(Flags, SCEV::FlagNUW); + if (BO->IsNSW) + Flags = setFlags(Flags, SCEV::FlagNSW); + } + } else if (GEPOperator *GEP = dyn_cast(BEValueV)) { + // If the increment is an inbounds GEP, then we know the address + // space cannot be wrapped around. We cannot make any guarantee + // about signed or unsigned overflow because pointers are + // unsigned but we may have a negative index from the base + // pointer. We can guarantee that no unsigned wrap occurs if the + // indices form a positive value. + if (GEP->isInBounds() && GEP->getOperand(0) == PN) { + Flags = setFlags(Flags, SCEV::FlagNW); + + const SCEV *Ptr = getSCEV(GEP->getPointerOperand()); + if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr))) + Flags = setFlags(Flags, SCEV::FlagNUW); } - if (FoundIndex != Add->getNumOperands()) { - // Create an add with everything but the specified operand. - SmallVector Ops; - for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i) - if (i != FoundIndex) - Ops.push_back(Add->getOperand(i)); - const SCEV *Accum = getAddExpr(Ops); - - // This is not a valid addrec if the step amount is varying each - // loop iteration, but is not itself an addrec in this loop. - if (isLoopInvariant(Accum, L) || - (isa(Accum) && - cast(Accum)->getLoop() == L)) { - SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap; - - if (auto BO = MatchBinaryOp(BEValueV, DT)) { - if (BO->Opcode == Instruction::Add && BO->LHS == PN) { - if (BO->IsNUW) - Flags = setFlags(Flags, SCEV::FlagNUW); - if (BO->IsNSW) - Flags = setFlags(Flags, SCEV::FlagNSW); - } - } else if (GEPOperator *GEP = dyn_cast(BEValueV)) { - // If the increment is an inbounds GEP, then we know the address - // space cannot be wrapped around. We cannot make any guarantee - // about signed or unsigned overflow because pointers are - // unsigned but we may have a negative index from the base - // pointer. We can guarantee that no unsigned wrap occurs if the - // indices form a positive value. - if (GEP->isInBounds() && GEP->getOperand(0) == PN) { - Flags = setFlags(Flags, SCEV::FlagNW); - - const SCEV *Ptr = getSCEV(GEP->getPointerOperand()); - if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr))) - Flags = setFlags(Flags, SCEV::FlagNUW); - } - - // We cannot transfer nuw and nsw flags from subtraction - // operations -- sub nuw X, Y is not the same as add nuw X, -Y - // for instance. - } - - const SCEV *StartVal = getSCEV(StartValueV); - const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags); - - // Okay, for the entire analysis of this edge we assumed the PHI - // to be symbolic. We now need to go back and purge all of the - // entries for the scalars that use the symbolic expression. - forgetSymbolicName(PN, SymbolicName); - ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV; - - // We can add Flags to the post-inc expression only if we - // know that it us *undefined behavior* for BEValueV to - // overflow. - if (auto *BEInst = dyn_cast(BEValueV)) - if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L)) - (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags); - - return PHISCEV; + // We cannot transfer nuw and nsw flags from subtraction + // operations -- sub nuw X, Y is not the same as add nuw X, -Y + // for instance. } - } - } else { - // Otherwise, this could be a loop like this: - // i = 0; for (j = 1; ..; ++j) { .... i = j; } - // In this case, j = {1,+,1} and BEValue is j. - // Because the other in-value of i (0) fits the evolution of BEValue - // i really is an addrec evolution. - // - // We can generalize this saying that i is the shifted value of BEValue - // by one iteration: - // PHI(f(0), f({1,+,1})) --> f({0,+,1}) - const SCEV *Shifted = SCEVShiftRewriter::rewrite(BEValue, L, *this); - const SCEV *Start = SCEVInitRewriter::rewrite(Shifted, L, *this); - if (Shifted != getCouldNotCompute() && - Start != getCouldNotCompute()) { + const SCEV *StartVal = getSCEV(StartValueV); - if (Start == StartVal) { - // Okay, for the entire analysis of this edge we assumed the PHI - // to be symbolic. We now need to go back and purge all of the - // entries for the scalars that use the symbolic expression. - forgetSymbolicName(PN, SymbolicName); - ValueExprMap[SCEVCallbackVH(PN, this)] = Shifted; - return Shifted; - } + const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags); + + // Okay, for the entire analysis of this edge we assumed the PHI + // to be symbolic. We now need to go back and purge all of the + // entries for the scalars that use the symbolic expression. + forgetSymbolicName(PN, SymbolicName); + ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV; + + // We can add Flags to the post-inc expression only if we + // know that it us *undefined behavior* for BEValueV to + // overflow. + if (auto *BEInst = dyn_cast(BEValueV)) + if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L)) + (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags); + + return PHISCEV; + } + } + } else { + // Otherwise, this could be a loop like this: + // i = 0; for (j = 1; ..; ++j) { .... i = j; } + // In this case, j = {1,+,1} and BEValue is j. + // Because the other in-value of i (0) fits the evolution of BEValue + // i really is an addrec evolution. + // + // We can generalize this saying that i is the shifted value of BEValue + // by one iteration: + // PHI(f(0), f({1,+,1})) --> f({0,+,1}) + const SCEV *Shifted = SCEVShiftRewriter::rewrite(BEValue, L, *this); + const SCEV *Start = SCEVInitRewriter::rewrite(Shifted, L, *this); + if (Shifted != getCouldNotCompute() && + Start != getCouldNotCompute()) { + const SCEV *StartVal = getSCEV(StartValueV); + if (Start == StartVal) { + // Okay, for the entire analysis of this edge we assumed the PHI + // to be symbolic. We now need to go back and purge all of the + // entries for the scalars that use the symbolic expression. + forgetSymbolicName(PN, SymbolicName); + ValueExprMap[SCEVCallbackVH(PN, this)] = Shifted; + return Shifted; } } - - // Remove the temporary PHI node SCEV that has been inserted while intending - // to create an AddRecExpr for this PHI node. We can not keep this temporary - // as it will prevent later (possibly simpler) SCEV expressions to be added - // to the ValueExprMap. - eraseValueFromMap(PN); } + // Remove the temporary PHI node SCEV that has been inserted while intending + // to create an AddRecExpr for this PHI node. We can not keep this temporary + // as it will prevent later (possibly simpler) SCEV expressions to be added + // to the ValueExprMap. + eraseValueFromMap(PN); + return nullptr; }