From: Evan Cheng Date: Thu, 25 Oct 2007 22:45:20 +0000 (+0000) Subject: Do not rewrite compare instruction using iv of a different stride if the new X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=5f8ebaa5c0c216b7dbb16b781895e4af36bfa39a;p=oota-llvm.git Do not rewrite compare instruction using iv of a different stride if the new stride may be rewritten using the stride of the compare instruction. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43367 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 5805e02a55a..fbe3171f81f 100644 --- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -177,11 +177,17 @@ private: void OptimizeIndvars(Loop *L); bool FindIVForUser(ICmpInst *Cond, IVStrideUse *&CondUse, const SCEVHandle *&CondStride); + bool RequiresTypeConversion(const Type *Ty, const Type *NewTy); unsigned CheckForIVReuse(bool, const SCEVHandle&, IVExpr&, const Type*, const std::vector& UsersToProcess); bool ValidStride(bool, int64_t, const std::vector& UsersToProcess); + SCEVHandle CollectIVUsers(const SCEVHandle &Stride, + IVUsersOfOneStride &Uses, + Loop *L, + bool &AllUsesAreAddresses, + std::vector &UsersToProcess); void StrengthReduceStridedIVUsers(const SCEVHandle &Stride, IVUsersOfOneStride &Uses, Loop *L, bool isOnlyStride); @@ -972,6 +978,19 @@ bool LoopStrengthReduce::ValidStride(bool HasBaseReg, return true; } +/// RequiresTypeConversion - Returns true if converting Ty to NewTy is not +/// a nop. +bool LoopStrengthReduce::RequiresTypeConversion(const Type *Ty, + const Type *NewTy) { + if (Ty == NewTy) + return false; + return (!Ty->canLosslesslyBitCastTo(NewTy) && + !(isa(NewTy) && + Ty->canLosslesslyBitCastTo(UIntPtrTy)) && + !(isa(Ty) && + NewTy->canLosslesslyBitCastTo(UIntPtrTy))); +} + /// CheckForIVReuse - Returns the multiple if the stride is the multiple /// of a previous stride and it is a legal value for the target addressing /// mode scale component and optional base reg. This allows the users of @@ -1001,7 +1020,8 @@ unsigned LoopStrengthReduce::CheckForIVReuse(bool HasBaseReg, IE = SI->second.IVs.end(); II != IE; ++II) // FIXME: Only handle base == 0 for now. // Only reuse previous IV if it would not require a type conversion. - if (isZero(II->Base) && II->Base->getType() == Ty) { + if (isZero(II->Base) && + !RequiresTypeConversion(II->Base->getType(),Ty)) { IV = *II; return Scale; } @@ -1030,23 +1050,16 @@ static bool isNonConstantNegative(const SCEVHandle &Expr) { return SC->getValue()->getValue().isNegative(); } -/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single -/// stride of IV. All of the users may have different starting values, and this -/// may not be the only stride (we know it is if isOnlyStride is true). -void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride, - IVUsersOfOneStride &Uses, - Loop *L, - bool isOnlyStride) { - // If all the users are moved to another stride, then there is nothing to do. - if (Uses.Users.size() == 0) - return; - - // Transform our list of users and offsets to a bit more complex table. In - // this new vector, each 'BasedUser' contains 'Base' the base of the - // strided accessas well as the old information from Uses. We progressively - // move information from the Base field to the Imm field, until we eventually - // have the full access expression to rewrite the use. - std::vector UsersToProcess; +// CollectIVUsers - Transform our list of users and offsets to a bit more +// complex table. In this new vector, each 'BasedUser' contains 'Base' the base +// of the strided accessas well as the old information from Uses. We +// progressively move information from the Base field to the Imm field, until +// we eventually have the full access expression to rewrite the use. +SCEVHandle LoopStrengthReduce::CollectIVUsers(const SCEVHandle &Stride, + IVUsersOfOneStride &Uses, + Loop *L, + bool &AllUsesAreAddresses, + std::vector &UsersToProcess) { UsersToProcess.reserve(Uses.Users.size()); for (unsigned i = 0, e = Uses.Users.size(); i != e; ++i) { UsersToProcess.push_back(BasedUser(Uses.Users[i], SE)); @@ -1070,17 +1083,6 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride, SCEVHandle CommonExprs = RemoveCommonExpressionsFromUseBases(UsersToProcess, SE); - // If we managed to find some expressions in common, we'll need to carry - // their value in a register and add it in for each use. This will take up - // a register operand, which potentially restricts what stride values are - // valid. - bool HaveCommonExprs = !isZero(CommonExprs); - - // Keep track if every use in UsersToProcess is an address. If they all are, - // we may be able to rewrite the entire collection of them in terms of a - // smaller-stride IV. - bool AllUsesAreAddresses = true; - // Next, figure out what we can represent in the immediate fields of // instructions. If we can represent anything there, move it to the imm // fields of the BasedUsers. We do this so that it increases the commonality @@ -1136,6 +1138,40 @@ void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride, } } + return CommonExprs; +} + +/// StrengthReduceStridedIVUsers - Strength reduce all of the users of a single +/// stride of IV. All of the users may have different starting values, and this +/// may not be the only stride (we know it is if isOnlyStride is true). +void LoopStrengthReduce::StrengthReduceStridedIVUsers(const SCEVHandle &Stride, + IVUsersOfOneStride &Uses, + Loop *L, + bool isOnlyStride) { + // If all the users are moved to another stride, then there is nothing to do. + if (Uses.Users.size() == 0) + return; + + // Keep track if every use in UsersToProcess is an address. If they all are, + // we may be able to rewrite the entire collection of them in terms of a + // smaller-stride IV. + bool AllUsesAreAddresses = true; + + // Transform our list of users and offsets to a bit more complex table. In + // this new vector, each 'BasedUser' contains 'Base' the base of the + // strided accessas well as the old information from Uses. We progressively + // move information from the Base field to the Imm field, until we eventually + // have the full access expression to rewrite the use. + std::vector UsersToProcess; + SCEVHandle CommonExprs = CollectIVUsers(Stride, Uses, L, AllUsesAreAddresses, + UsersToProcess); + + // If we managed to find some expressions in common, we'll need to carry + // their value in a register and add it in for each use. This will take up + // a register operand, which potentially restricts what stride values are + // valid. + bool HaveCommonExprs = !isZero(CommonExprs); + // If all uses are addresses, check if it is possible to reuse an IV with a // stride that is a factor of this stride. And that the multiple is a number // that can be encoded in the scale field of the target addressing mode. And @@ -1424,9 +1460,6 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond, if (StrideOrder.size() < 2 || IVUsesByStride[*CondStride].Users.size() != 1) return Cond; - // FIXME: loosen this restriction? - if (!isa(CondUse->Offset)) - return Cond; const SCEVConstant *SC = dyn_cast(*CondStride); if (!SC) return Cond; ConstantInt *C = dyn_cast(Cond->getOperand(1)); @@ -1478,11 +1511,22 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond, continue; } - // FIXME: allow reuse of iv of a smaller type? NewCmpTy = NewIncV->getType(); - if (!CmpTy->canLosslesslyBitCastTo(NewCmpTy) && - !(isa(NewCmpTy) && - CmpTy->canLosslesslyBitCastTo(UIntPtrTy))) { + if (RequiresTypeConversion(CmpTy, NewCmpTy)) { + // FIXME: allow reuse of iv of a smaller type? + NewCmpVal = CmpVal; + continue; + } + + bool AllUsesAreAddresses = true; + std::vector UsersToProcess; + SCEVHandle CommonExprs = CollectIVUsers(SI->first, SI->second, L, + AllUsesAreAddresses, + UsersToProcess); + // Avoid rewriting the compare instruction with an iv of new stride + // if it's likely the new stride uses will be rewritten using the + if (AllUsesAreAddresses && + ValidStride(!isZero(CommonExprs), Scale, UsersToProcess)) { NewCmpVal = CmpVal; continue; }