R600: Use LDS and vectors for private memory

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211110 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 365 insertions, 0 deletions

diff --git a/lib/Target/R600/AMDGPUPromoteAlloca.cpp b/lib/Target/R600/AMDGPUPromoteAlloca.cpp
new file mode 100644
index 0000000000..2d3a7fdd4f
--- /dev/null
+++ b/lib/Target/R600/AMDGPUPromoteAlloca.cpp
@@ -0,0 +1,365 @@
+//===-- AMDGPUPromoteAlloca.cpp - Promote Allocas -------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass eliminates allocas by either converting them into vectors or
+// by migrating them to local address space.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AMDGPU.h"
+#include "AMDGPUSubtarget.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InstVisitor.h"
+#include "llvm/Support/Debug.h"
+
+#define DEBUG_TYPE "amdgpu-promote-alloca"
+
+using namespace llvm;
+
+namespace {
+
+class AMDGPUPromoteAlloca : public FunctionPass,
+                       public InstVisitor<AMDGPUPromoteAlloca> {
+
+  static char ID;
+  Module *Mod;
+  const AMDGPUSubtarget &ST;
+  int LocalMemAvailable;
+
+public:
+  AMDGPUPromoteAlloca(const AMDGPUSubtarget &st) : FunctionPass(ID), ST(st),
+                                                   LocalMemAvailable(0) { }
+  virtual bool doInitialization(Module &M);
+  virtual bool runOnFunction(Function &F);
+  virtual const char *getPassName() const {
+    return "AMDGPU Promote Alloca";
+  }
+  void visitAlloca(AllocaInst &I);
+};
+
+} // End anonymous namespace
+
+char AMDGPUPromoteAlloca::ID = 0;
+
+bool AMDGPUPromoteAlloca::doInitialization(Module &M) {
+  Mod = &M;
+  return false;
+}
+
+bool AMDGPUPromoteAlloca::runOnFunction(Function &F) {
+
+  const FunctionType *FTy = F.getFunctionType();
+
+  LocalMemAvailable = ST.getLocalMemorySize();
+
+
+  // If the function has any arguments in the local address space, then it's
+  // possible these arguments require the entire local memory space, so
+  // we cannot use local memory in the pass.
+  for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) {
+    const Type *ParamTy = FTy->getParamType(i);
+    if (ParamTy->isPointerTy() &&
+        ParamTy->getPointerAddressSpace() == AMDGPUAS::LOCAL_ADDRESS) {
+      LocalMemAvailable = 0;
+      DEBUG(dbgs() << "Function has local memory argument.  Promoting to "
+                      "local memory disabled.\n");
+      break;
+    }
+  }
+
+  if (LocalMemAvailable > 0) {
+    // Check how much local memory is being used by global objects
+    for (Module::global_iterator I = Mod->global_begin(),
+                                 E = Mod->global_end(); I != E; ++I) {
+      GlobalVariable *GV = I;
+      PointerType *GVTy = GV->getType();
+      if (GVTy->getAddressSpace() != AMDGPUAS::LOCAL_ADDRESS)
+        continue;
+      for (Value::use_iterator U = GV->use_begin(),
+                               UE = GV->use_end(); U != UE; ++U) {
+        Instruction *Use = dyn_cast<Instruction>(*U);
+        if (!Use)
+          continue;
+        if (Use->getParent()->getParent() == &F)
+          LocalMemAvailable -=
+              Mod->getDataLayout()->getTypeAllocSize(GVTy->getElementType());
+      }
+    }
+  }
+
+  LocalMemAvailable = std::max(0, LocalMemAvailable);
+  DEBUG(dbgs() << LocalMemAvailable << "bytes free in local memory.\n");
+
+  visit(F);
+
+  return false;
+}
+
+static VectorType *arrayTypeToVecType(const Type *ArrayTy) {
+  return VectorType::get(ArrayTy->getArrayElementType(),
+                         ArrayTy->getArrayNumElements());
+}
+
+static Value* calculateVectorIndex(Value *Ptr,
+                                  std::map<GetElementPtrInst*, Value*> GEPIdx) {
+  if (isa<AllocaInst>(Ptr))
+    return Constant::getNullValue(Type::getInt32Ty(Ptr->getContext()));
+
+  GetElementPtrInst *GEP = cast<GetElementPtrInst>(Ptr);
+
+  return GEPIdx[GEP];
+}
+
+static Value* GEPToVectorIndex(GetElementPtrInst *GEP) {
+  // FIXME we only support simple cases
+  if (GEP->getNumOperands() != 3)
+    return NULL;
+
+  ConstantInt *I0 = dyn_cast<ConstantInt>(GEP->getOperand(1));
+  if (!I0 || !I0->isZero())
+    return NULL;
+
+  return GEP->getOperand(2);
+}
+
+static bool tryPromoteAllocaToVector(AllocaInst *Alloca) {
+  Type *AllocaTy = Alloca->getAllocatedType();
+
+  DEBUG(dbgs() << "Alloca Candidate for vectorization \n");
+
+  // FIXME: There is no reason why we can't support larger arrays, we
+  // are just being conservative for now.
+  if (!AllocaTy->isArrayTy() ||
+      AllocaTy->getArrayElementType()->isVectorTy() ||
+      AllocaTy->getArrayNumElements() > 4) {
+
+    DEBUG(dbgs() << "  Cannot convert type to vector");
+    return false;
+  }
+
+  std::map<GetElementPtrInst*, Value*> GEPVectorIdx;
+  std::vector<Value*> WorkList;
+  for (User *AllocaUser : Alloca->users()) {
+    GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(AllocaUser);
+    if (!GEP) {
+      WorkList.push_back(AllocaUser);
+      continue;
+    }
+
+    Value *Index = GEPToVectorIndex(GEP);
+
+    // If we can't compute a vector index from this GEP, then we can't
+    // promote this alloca to vector.
+    if (!Index) {
+      DEBUG(dbgs() << "  Cannot compute vector index for GEP " << *GEP << "\n");
+      return false;
+    }
+
+    GEPVectorIdx[GEP] = Index;
+    for (User *GEPUser : AllocaUser->users()) {
+      WorkList.push_back(GEPUser);
+    }
+  }
+
+  VectorType *VectorTy = arrayTypeToVecType(AllocaTy);
+
+  DEBUG(dbgs() << "  Converting alloca to vector "; AllocaTy->dump();
+        dbgs() << " -> "; VectorTy->dump(); dbgs() << "\n");
+
+  for (std::vector<Value*>::iterator I = WorkList.begin(),
+                                     E = WorkList.end(); I != E; ++I) {
+    Instruction *Inst = cast<Instruction>(*I);
+    IRBuilder<> Builder(Inst);
+    switch (Inst->getOpcode()) {
+    case Instruction::Load: {
+      Value *Ptr = Inst->getOperand(0);
+      Value *Index = calculateVectorIndex(Ptr, GEPVectorIdx);
+      Value *BitCast = Builder.CreateBitCast(Alloca, VectorTy->getPointerTo(0));
+      Value *VecValue = Builder.CreateLoad(BitCast);
+      Value *ExtractElement = Builder.CreateExtractElement(VecValue, Index);
+      Inst->replaceAllUsesWith(ExtractElement);
+      Inst->eraseFromParent();
+      break;
+    }
+    case Instruction::Store: {
+      Value *Ptr = Inst->getOperand(1);
+      Value *Index = calculateVectorIndex(Ptr, GEPVectorIdx);
+      Value *BitCast = Builder.CreateBitCast(Alloca, VectorTy->getPointerTo(0));
+      Value *VecValue = Builder.CreateLoad(BitCast);
+      Value *NewVecValue = Builder.CreateInsertElement(VecValue,
+                                                       Inst->getOperand(0),
+                                                       Index);
+      Builder.CreateStore(NewVecValue, BitCast);
+      Inst->eraseFromParent();
+      break;
+    }
+    case Instruction::BitCast:
+      break;
+
+    default:
+      Inst->dump();
+      llvm_unreachable("Do not know how to replace this instruction "
+                              "with vector op");
+    }
+  }
+  return true;
+}
+
+static void collectUsesWithPtrTypes(Value *Val, std::vector<Value*> &WorkList) {
+  for (User *User : Val->users()) {
+    if(std::find(WorkList.begin(), WorkList.end(), User) != WorkList.end())
+      continue;
+    if (isa<CallInst>(User)) {
+      WorkList.push_back(User);
+      continue;
+    }
+    if (!User->getType()->isPointerTy())
+      continue;
+    WorkList.push_back(User);
+    collectUsesWithPtrTypes(User, WorkList);
+  }
+}
+
+void AMDGPUPromoteAlloca::visitAlloca(AllocaInst &I) {
+  IRBuilder<> Builder(&I);
+
+  // First try to replace the alloca with a vector
+  Type *AllocaTy = I.getAllocatedType();
+
+  DEBUG(dbgs() << "Trying to promote " << I);
+
+  if (tryPromoteAllocaToVector(&I))
+    return;
+
+  DEBUG(dbgs() << " alloca is not a candidate for vectorization.\n");
+
+  // FIXME: This is the maximum work group size.  We should try to get
+  // value from the reqd_work_group_size function attribute if it is
+  // available.
+  unsigned WorkGroupSize = 256;
+  int AllocaSize = WorkGroupSize *
+      Mod->getDataLayout()->getTypeAllocSize(AllocaTy);
+
+  if (AllocaSize > LocalMemAvailable) {
+    DEBUG(dbgs() << " Not enough local memory to promote alloca.\n");
+    return;
+  }
+
+  DEBUG(dbgs() << "Promoting alloca to local memory\n");
+  LocalMemAvailable -= AllocaSize;
+
+  GlobalVariable *GV = new GlobalVariable(
+      *Mod, ArrayType::get(I.getAllocatedType(), 256), false,
+      GlobalValue::ExternalLinkage, 0, I.getName(), 0,
+      GlobalVariable::NotThreadLocal, AMDGPUAS::LOCAL_ADDRESS);
+
+  FunctionType *FTy = FunctionType::get(
+      Type::getInt32Ty(Mod->getContext()), false);
+  AttributeSet AttrSet;
+  AttrSet.addAttribute(Mod->getContext(), 0, Attribute::ReadNone);
+
+  Value *ReadLocalSizeY = Mod->getOrInsertFunction(
+      "llvm.r600.read.local.size.y", FTy, AttrSet);
+  Value *ReadLocalSizeZ = Mod->getOrInsertFunction(
+      "llvm.r600.read.local.size.z", FTy, AttrSet);
+  Value *ReadTIDIGX = Mod->getOrInsertFunction(
+      "llvm.r600.read.tidig.x", FTy, AttrSet);
+  Value *ReadTIDIGY = Mod->getOrInsertFunction(
+      "llvm.r600.read.tidig.y", FTy, AttrSet);
+  Value *ReadTIDIGZ = Mod->getOrInsertFunction(
+      "llvm.r600.read.tidig.z", FTy, AttrSet);
+
+
+  Value *TCntY = Builder.CreateCall(ReadLocalSizeY);
+  Value *TCntZ = Builder.CreateCall(ReadLocalSizeZ);
+  Value *TIdX  = Builder.CreateCall(ReadTIDIGX);
+  Value *TIdY  = Builder.CreateCall(ReadTIDIGY);
+  Value *TIdZ  = Builder.CreateCall(ReadTIDIGZ);
+
+  Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ);
+  Tmp0 = Builder.CreateMul(Tmp0, TIdX);
+  Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ);
+  Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
+  TID = Builder.CreateAdd(TID, TIdZ);
+
+  std::vector<Value*> Indices;
+  Indices.push_back(Constant::getNullValue(Type::getInt32Ty(Mod->getContext())));
+  Indices.push_back(TID);
+
+  Value *Offset = Builder.CreateGEP(GV, Indices);
+  I.mutateType(Offset->getType());
+  I.replaceAllUsesWith(Offset);
+  I.eraseFromParent();
+
+  std::vector<Value*> WorkList;
+
+  collectUsesWithPtrTypes(Offset, WorkList);
+
+  for (std::vector<Value*>::iterator i = WorkList.begin(),
+                                     e = WorkList.end(); i != e; ++i) {
+    Value *V = *i;
+    CallInst *Call = dyn_cast<CallInst>(V);
+    if (!Call) {
+      Type *EltTy = V->getType()->getPointerElementType();
+      PointerType *NewTy = PointerType::get(EltTy, AMDGPUAS::LOCAL_ADDRESS);
+      V->mutateType(NewTy);
+      continue;
+    }
+
+    IntrinsicInst *Intr = dyn_cast<IntrinsicInst>(Call);
+    if (!Intr) {
+      std::vector<Type*> ArgTypes;
+      for (unsigned ArgIdx = 0, ArgEnd = Call->getNumArgOperands();
+                                ArgIdx != ArgEnd; ++ArgIdx) {
+        ArgTypes.push_back(Call->getArgOperand(ArgIdx)->getType());
+      }
+      Function *F = Call->getCalledFunction();
+      FunctionType *NewType = FunctionType::get(Call->getType(), ArgTypes,
+                                                F->isVarArg());
+      Constant *C = Mod->getOrInsertFunction(StringRef(F->getName().str() + ".local"), NewType,
+                                             F->getAttributes());
+      Function *NewF = cast<Function>(C);
+      Call->setCalledFunction(NewF);
+      continue;
+    }
+
+    Builder.SetInsertPoint(Intr);
+    switch (Intr->getIntrinsicID()) {
+    case Intrinsic::lifetime_start:
+    case Intrinsic::lifetime_end:
+      // These intrinsics are for address space 0 only
+      Intr->eraseFromParent();
+      continue;
+    case Intrinsic::memcpy: {
+      MemCpyInst *MemCpy = cast<MemCpyInst>(Intr);
+      Builder.CreateMemCpy(MemCpy->getRawDest(), MemCpy->getRawSource(),
+                           MemCpy->getLength(), MemCpy->getAlignment(),
+                           MemCpy->isVolatile());
+      Intr->eraseFromParent();
+      continue;
+    }
+    case Intrinsic::memset: {
+      MemSetInst *MemSet = cast<MemSetInst>(Intr);
+      Builder.CreateMemSet(MemSet->getRawDest(), MemSet->getValue(),
+                           MemSet->getLength(), MemSet->getAlignment(),
+                           MemSet->isVolatile());
+      Intr->eraseFromParent();
+      continue;
+    }
+    default:
+      Intr->dump();
+      llvm_unreachable("Don't know how to promote alloca intrinsic use.");
+    }
+  }
+}
+
+FunctionPass *llvm::createAMDGPUPromoteAlloca(const AMDGPUSubtarget &ST) {
+  return new AMDGPUPromoteAlloca(ST);
+}