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Diffstat (limited to 'llvm/lib/Target/NVPTX/NVPTXFavorNonGenericAddrSpaces.cpp')
| -rw-r--r-- | llvm/lib/Target/NVPTX/NVPTXFavorNonGenericAddrSpaces.cpp | 289 |
1 files changed, 0 insertions, 289 deletions
diff --git a/llvm/lib/Target/NVPTX/NVPTXFavorNonGenericAddrSpaces.cpp b/llvm/lib/Target/NVPTX/NVPTXFavorNonGenericAddrSpaces.cpp deleted file mode 100644 index 7c5a54162d7..00000000000 --- a/llvm/lib/Target/NVPTX/NVPTXFavorNonGenericAddrSpaces.cpp +++ /dev/null @@ -1,289 +0,0 @@ -//===-- NVPTXFavorNonGenericAddrSpace.cpp - ---------------------*- C++ -*-===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// FIXME: This pass is deprecated in favor of NVPTXInferAddressSpaces, which -// uses a new algorithm that handles pointer induction variables. -// -// When a load/store accesses the generic address space, checks whether the -// address is casted from a non-generic address space. If so, remove this -// addrspacecast because accessing non-generic address spaces is typically -// faster. Besides removing addrspacecasts directly used by loads/stores, this -// optimization also recursively traces into a GEP's pointer operand and a -// bitcast's source to find more eliminable addrspacecasts. -// -// For instance, the code below loads a float from an array allocated in -// addrspace(3). -// -// %0 = addrspacecast [10 x float] addrspace(3)* @a to [10 x float]* -// %1 = gep [10 x float]* %0, i64 0, i64 %i -// %2 = bitcast float* %1 to i32* -// %3 = load i32* %2 ; emits ld.u32 -// -// First, function hoistAddrSpaceCastFrom reorders the addrspacecast, the GEP, -// and the bitcast to expose more optimization opportunities to function -// optimizeMemoryInst. The intermediate code looks like: -// -// %0 = gep [10 x float] addrspace(3)* @a, i64 0, i64 %i -// %1 = bitcast float addrspace(3)* %0 to i32 addrspace(3)* -// %2 = addrspacecast i32 addrspace(3)* %1 to i32* -// %3 = load i32* %2 ; still emits ld.u32, but will be optimized shortly -// -// Then, function optimizeMemoryInstruction detects a load from addrspacecast'ed -// generic pointers, and folds the load and the addrspacecast into a load from -// the original address space. The final code looks like: -// -// %0 = gep [10 x float] addrspace(3)* @a, i64 0, i64 %i -// %1 = bitcast float addrspace(3)* %0 to i32 addrspace(3)* -// %3 = load i32 addrspace(3)* %1 ; emits ld.shared.f32 -// -// This pass may remove an addrspacecast in a different BB. Therefore, we -// implement it as a FunctionPass. -// -// TODO: -// The current implementation doesn't handle PHINodes. Eliminating -// addrspacecasts used by PHINodes is trickier because PHINodes can introduce -// loops in data flow. For example, -// -// %generic.input = addrspacecast float addrspace(3)* %input to float* -// loop: -// %y = phi [ %generic.input, %y2 ] -// %y2 = getelementptr %y, 1 -// %v = load %y2 -// br ..., label %loop, ... -// -// Marking %y2 shared depends on marking %y shared, but %y also data-flow -// depends on %y2. We probably need an iterative fix-point algorithm on handle -// this case. -// -//===----------------------------------------------------------------------===// - -#include "NVPTX.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/Operator.h" -#include "llvm/Support/CommandLine.h" - -using namespace llvm; - -// An option to disable this optimization. Enable it by default. -static cl::opt<bool> DisableFavorNonGeneric( - "disable-nvptx-favor-non-generic", - cl::init(false), - cl::desc("Do not convert generic address space usage " - "to non-generic address space usage"), - cl::Hidden); - -namespace { -/// \brief NVPTXFavorNonGenericAddrSpaces -class NVPTXFavorNonGenericAddrSpaces : public FunctionPass { -public: - static char ID; - NVPTXFavorNonGenericAddrSpaces() : FunctionPass(ID) {} - bool runOnFunction(Function &F) override; - -private: - /// Optimizes load/store instructions. Idx is the index of the pointer operand - /// (0 for load, and 1 for store). Returns true if it changes anything. - bool optimizeMemoryInstruction(Instruction *I, unsigned Idx); - /// Recursively traces into a GEP's pointer operand or a bitcast's source to - /// find an eliminable addrspacecast, and hoists that addrspacecast to the - /// outermost level. For example, this function transforms - /// bitcast(gep(gep(addrspacecast(X)))) - /// to - /// addrspacecast(bitcast(gep(gep(X)))). - /// - /// This reordering exposes to optimizeMemoryInstruction more - /// optimization opportunities on loads and stores. - /// - /// If this function successfully hoists an eliminable addrspacecast or V is - /// already such an addrspacecast, it returns the transformed value (which is - /// guaranteed to be an addrspacecast); otherwise, it returns nullptr. - Value *hoistAddrSpaceCastFrom(Value *V, int Depth = 0); - /// Helper function for GEPs. - Value *hoistAddrSpaceCastFromGEP(GEPOperator *GEP, int Depth); - /// Helper function for bitcasts. - Value *hoistAddrSpaceCastFromBitCast(BitCastOperator *BC, int Depth); -}; -} - -char NVPTXFavorNonGenericAddrSpaces::ID = 0; - -namespace llvm { -void initializeNVPTXFavorNonGenericAddrSpacesPass(PassRegistry &); -} -INITIALIZE_PASS(NVPTXFavorNonGenericAddrSpaces, "nvptx-favor-non-generic", - "Remove unnecessary non-generic-to-generic addrspacecasts", - false, false) - -// Decides whether V is an addrspacecast and shortcutting V in load/store is -// valid and beneficial. -static bool isEliminableAddrSpaceCast(Value *V) { - // Returns false if V is not even an addrspacecast. - Operator *Cast = dyn_cast<Operator>(V); - if (Cast == nullptr || Cast->getOpcode() != Instruction::AddrSpaceCast) - return false; - - Value *Src = Cast->getOperand(0); - PointerType *SrcTy = cast<PointerType>(Src->getType()); - PointerType *DestTy = cast<PointerType>(Cast->getType()); - // TODO: For now, we only handle the case where the addrspacecast only changes - // the address space but not the type. If the type also changes, we could - // still get rid of the addrspacecast by adding an extra bitcast, but we - // rarely see such scenarios. - if (SrcTy->getElementType() != DestTy->getElementType()) - return false; - - // Checks whether the addrspacecast is from a non-generic address space to the - // generic address space. - return (SrcTy->getAddressSpace() != AddressSpace::ADDRESS_SPACE_GENERIC && - DestTy->getAddressSpace() == AddressSpace::ADDRESS_SPACE_GENERIC); -} - -Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFromGEP( - GEPOperator *GEP, int Depth) { - Value *NewOperand = - hoistAddrSpaceCastFrom(GEP->getPointerOperand(), Depth + 1); - if (NewOperand == nullptr) - return nullptr; - - // hoistAddrSpaceCastFrom returns an eliminable addrspacecast or nullptr. - assert(isEliminableAddrSpaceCast(NewOperand)); - Operator *Cast = cast<Operator>(NewOperand); - - SmallVector<Value *, 8> Indices(GEP->idx_begin(), GEP->idx_end()); - Value *NewASC; - if (Instruction *GEPI = dyn_cast<Instruction>(GEP)) { - // GEP = gep (addrspacecast X), indices - // => - // NewGEP = gep X, indices - // NewASC = addrspacecast NewGEP - GetElementPtrInst *NewGEP = GetElementPtrInst::Create( - GEP->getSourceElementType(), Cast->getOperand(0), Indices, - "", GEPI); - NewGEP->setIsInBounds(GEP->isInBounds()); - NewGEP->takeName(GEP); - NewASC = new AddrSpaceCastInst(NewGEP, GEP->getType(), "", GEPI); - // Without RAUWing GEP, the compiler would visit GEP again and emit - // redundant instructions. This is exercised in test @rauw in - // access-non-generic.ll. - GEP->replaceAllUsesWith(NewASC); - } else { - // GEP is a constant expression. - Constant *NewGEP = ConstantExpr::getGetElementPtr( - GEP->getSourceElementType(), cast<Constant>(Cast->getOperand(0)), - Indices, GEP->isInBounds()); - NewASC = ConstantExpr::getAddrSpaceCast(NewGEP, GEP->getType()); - } - return NewASC; -} - -Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFromBitCast( - BitCastOperator *BC, int Depth) { - Value *NewOperand = hoistAddrSpaceCastFrom(BC->getOperand(0), Depth + 1); - if (NewOperand == nullptr) - return nullptr; - - // hoistAddrSpaceCastFrom returns an eliminable addrspacecast or nullptr. - assert(isEliminableAddrSpaceCast(NewOperand)); - Operator *Cast = cast<Operator>(NewOperand); - - // Cast = addrspacecast Src - // BC = bitcast Cast - // => - // Cast' = bitcast Src - // BC' = addrspacecast Cast' - Value *Src = Cast->getOperand(0); - Type *TypeOfNewCast = - PointerType::get(BC->getType()->getPointerElementType(), - Src->getType()->getPointerAddressSpace()); - Value *NewBC; - if (BitCastInst *BCI = dyn_cast<BitCastInst>(BC)) { - Value *NewCast = new BitCastInst(Src, TypeOfNewCast, "", BCI); - NewBC = new AddrSpaceCastInst(NewCast, BC->getType(), "", BCI); - NewBC->takeName(BC); - // Without RAUWing BC, the compiler would visit BC again and emit - // redundant instructions. This is exercised in test @rauw in - // access-non-generic.ll. - BC->replaceAllUsesWith(NewBC); - } else { - // BC is a constant expression. - Constant *NewCast = - ConstantExpr::getBitCast(cast<Constant>(Src), TypeOfNewCast); - NewBC = ConstantExpr::getAddrSpaceCast(NewCast, BC->getType()); - } - return NewBC; -} - -Value *NVPTXFavorNonGenericAddrSpaces::hoistAddrSpaceCastFrom(Value *V, - int Depth) { - // Returns V if V is already an eliminable addrspacecast. - if (isEliminableAddrSpaceCast(V)) - return V; - - // Limit the depth to prevent this recursive function from running too long. - const int MaxDepth = 20; - if (Depth >= MaxDepth) - return nullptr; - - // If V is a GEP or bitcast, hoist the addrspacecast if any from its pointer - // operand. This enables optimizeMemoryInstruction to shortcut addrspacecasts - // that are not directly used by the load/store. - if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) - return hoistAddrSpaceCastFromGEP(GEP, Depth); - - if (BitCastOperator *BC = dyn_cast<BitCastOperator>(V)) - return hoistAddrSpaceCastFromBitCast(BC, Depth); - - return nullptr; -} - -bool NVPTXFavorNonGenericAddrSpaces::optimizeMemoryInstruction(Instruction *MI, - unsigned Idx) { - Value *NewOperand = hoistAddrSpaceCastFrom(MI->getOperand(Idx)); - if (NewOperand == nullptr) - return false; - - // load/store (addrspacecast X) => load/store X if shortcutting the - // addrspacecast is valid and can improve performance. - // - // e.g., - // %1 = addrspacecast float addrspace(3)* %0 to float* - // %2 = load float* %1 - // -> - // %2 = load float addrspace(3)* %0 - // - // Note: the addrspacecast can also be a constant expression. - assert(isEliminableAddrSpaceCast(NewOperand)); - Operator *ASC = dyn_cast<Operator>(NewOperand); - MI->setOperand(Idx, ASC->getOperand(0)); - return true; -} - -bool NVPTXFavorNonGenericAddrSpaces::runOnFunction(Function &F) { - if (DisableFavorNonGeneric || skipFunction(F)) - return false; - - bool Changed = false; - for (BasicBlock &B : F) { - for (Instruction &I : B) { - if (isa<LoadInst>(I)) { - // V = load P - Changed |= optimizeMemoryInstruction(&I, 0); - } else if (isa<StoreInst>(I)) { - // store V, P - Changed |= optimizeMemoryInstruction(&I, 1); - } - } - } - return Changed; -} - -FunctionPass *llvm::createNVPTXFavorNonGenericAddrSpacesPass() { - return new NVPTXFavorNonGenericAddrSpaces(); -} |
