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230 lines
8.0 KiB
C++
230 lines
8.0 KiB
C++
//===- NVPTXLowerAggrCopies.cpp - ------------------------------*- C++ -*--===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// Lower aggregate copies, memset, memcpy, memmov intrinsics into loops when
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// the size is large or is not a compile-time constant.
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//
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//===----------------------------------------------------------------------===//
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#include "NVPTXLowerAggrCopies.h"
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#include "llvm/CodeGen/MachineFunctionAnalysis.h"
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#include "llvm/CodeGen/StackProtector.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/Support/Debug.h"
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#define DEBUG_TYPE "nvptx"
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using namespace llvm;
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namespace {
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// actual analysis class, which is a functionpass
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struct NVPTXLowerAggrCopies : public FunctionPass {
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static char ID;
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NVPTXLowerAggrCopies() : FunctionPass(ID) {}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addPreserved<MachineFunctionAnalysis>();
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AU.addPreserved<StackProtector>();
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}
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bool runOnFunction(Function &F) override;
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static const unsigned MaxAggrCopySize = 128;
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const char *getPassName() const override {
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return "Lower aggregate copies/intrinsics into loops";
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}
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};
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} // namespace
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char NVPTXLowerAggrCopies::ID = 0;
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// Lower MemTransferInst or load-store pair to loop
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static void convertTransferToLoop(
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Instruction *splitAt, Value *srcAddr, Value *dstAddr, Value *len,
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//unsigned numLoads,
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bool srcVolatile, bool dstVolatile, LLVMContext &Context, Function &F) {
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Type *indType = len->getType();
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BasicBlock *origBB = splitAt->getParent();
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BasicBlock *newBB = splitAt->getParent()->splitBasicBlock(splitAt, "split");
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BasicBlock *loopBB = BasicBlock::Create(Context, "loadstoreloop", &F, newBB);
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origBB->getTerminator()->setSuccessor(0, loopBB);
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IRBuilder<> builder(origBB, origBB->getTerminator());
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// srcAddr and dstAddr are expected to be pointer types,
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// so no check is made here.
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unsigned srcAS = cast<PointerType>(srcAddr->getType())->getAddressSpace();
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unsigned dstAS = cast<PointerType>(dstAddr->getType())->getAddressSpace();
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// Cast pointers to (char *)
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srcAddr = builder.CreateBitCast(srcAddr, Type::getInt8PtrTy(Context, srcAS));
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dstAddr = builder.CreateBitCast(dstAddr, Type::getInt8PtrTy(Context, dstAS));
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IRBuilder<> loop(loopBB);
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// The loop index (ind) is a phi node.
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PHINode *ind = loop.CreatePHI(indType, 0);
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// Incoming value for ind is 0
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ind->addIncoming(ConstantInt::get(indType, 0), origBB);
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// load from srcAddr+ind
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Value *val = loop.CreateLoad(loop.CreateGEP(loop.getInt8Ty(), srcAddr, ind),
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srcVolatile);
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// store at dstAddr+ind
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loop.CreateStore(val, loop.CreateGEP(loop.getInt8Ty(), dstAddr, ind),
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dstVolatile);
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// The value for ind coming from backedge is (ind + 1)
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Value *newind = loop.CreateAdd(ind, ConstantInt::get(indType, 1));
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ind->addIncoming(newind, loopBB);
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loop.CreateCondBr(loop.CreateICmpULT(newind, len), loopBB, newBB);
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}
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// Lower MemSetInst to loop
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static void convertMemSetToLoop(Instruction *splitAt, Value *dstAddr,
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Value *len, Value *val, LLVMContext &Context,
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Function &F) {
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BasicBlock *origBB = splitAt->getParent();
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BasicBlock *newBB = splitAt->getParent()->splitBasicBlock(splitAt, "split");
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BasicBlock *loopBB = BasicBlock::Create(Context, "loadstoreloop", &F, newBB);
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origBB->getTerminator()->setSuccessor(0, loopBB);
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IRBuilder<> builder(origBB, origBB->getTerminator());
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unsigned dstAS = cast<PointerType>(dstAddr->getType())->getAddressSpace();
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// Cast pointer to the type of value getting stored
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dstAddr =
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builder.CreateBitCast(dstAddr, PointerType::get(val->getType(), dstAS));
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IRBuilder<> loop(loopBB);
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PHINode *ind = loop.CreatePHI(len->getType(), 0);
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ind->addIncoming(ConstantInt::get(len->getType(), 0), origBB);
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loop.CreateStore(val, loop.CreateGEP(val->getType(), dstAddr, ind), false);
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Value *newind = loop.CreateAdd(ind, ConstantInt::get(len->getType(), 1));
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ind->addIncoming(newind, loopBB);
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loop.CreateCondBr(loop.CreateICmpULT(newind, len), loopBB, newBB);
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}
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bool NVPTXLowerAggrCopies::runOnFunction(Function &F) {
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SmallVector<LoadInst *, 4> aggrLoads;
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SmallVector<MemTransferInst *, 4> aggrMemcpys;
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SmallVector<MemSetInst *, 4> aggrMemsets;
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const DataLayout &DL = F.getParent()->getDataLayout();
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LLVMContext &Context = F.getParent()->getContext();
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//
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// Collect all the aggrLoads, aggrMemcpys and addrMemsets.
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//
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for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
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for (BasicBlock::iterator II = BI->begin(), IE = BI->end(); II != IE;
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++II) {
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if (LoadInst *load = dyn_cast<LoadInst>(II)) {
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if (!load->hasOneUse())
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continue;
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if (DL.getTypeStoreSize(load->getType()) < MaxAggrCopySize)
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continue;
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User *use = load->user_back();
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if (StoreInst *store = dyn_cast<StoreInst>(use)) {
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if (store->getOperand(0) != load)
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continue;
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aggrLoads.push_back(load);
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}
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} else if (MemTransferInst *intr = dyn_cast<MemTransferInst>(II)) {
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Value *len = intr->getLength();
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// If the number of elements being copied is greater
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// than MaxAggrCopySize, lower it to a loop
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if (ConstantInt *len_int = dyn_cast<ConstantInt>(len)) {
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if (len_int->getZExtValue() >= MaxAggrCopySize) {
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aggrMemcpys.push_back(intr);
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}
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} else {
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// turn variable length memcpy/memmov into loop
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aggrMemcpys.push_back(intr);
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}
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} else if (MemSetInst *memsetintr = dyn_cast<MemSetInst>(II)) {
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Value *len = memsetintr->getLength();
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if (ConstantInt *len_int = dyn_cast<ConstantInt>(len)) {
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if (len_int->getZExtValue() >= MaxAggrCopySize) {
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aggrMemsets.push_back(memsetintr);
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}
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} else {
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// turn variable length memset into loop
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aggrMemsets.push_back(memsetintr);
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}
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}
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}
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}
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if ((aggrLoads.size() == 0) && (aggrMemcpys.size() == 0) &&
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(aggrMemsets.size() == 0))
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return false;
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//
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// Do the transformation of an aggr load/copy/set to a loop
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//
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for (unsigned i = 0, e = aggrLoads.size(); i != e; ++i) {
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LoadInst *load = aggrLoads[i];
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StoreInst *store = dyn_cast<StoreInst>(*load->user_begin());
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Value *srcAddr = load->getOperand(0);
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Value *dstAddr = store->getOperand(1);
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unsigned numLoads = DL.getTypeStoreSize(load->getType());
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Value *len = ConstantInt::get(Type::getInt32Ty(Context), numLoads);
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convertTransferToLoop(store, srcAddr, dstAddr, len, load->isVolatile(),
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store->isVolatile(), Context, F);
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store->eraseFromParent();
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load->eraseFromParent();
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}
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for (unsigned i = 0, e = aggrMemcpys.size(); i != e; ++i) {
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MemTransferInst *cpy = aggrMemcpys[i];
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Value *len = cpy->getLength();
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// llvm 2.7 version of memcpy does not have volatile
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// operand yet. So always making it non-volatile
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// optimistically, so that we don't see unnecessary
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// st.volatile in ptx
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convertTransferToLoop(cpy, cpy->getSource(), cpy->getDest(), len, false,
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false, Context, F);
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cpy->eraseFromParent();
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}
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for (unsigned i = 0, e = aggrMemsets.size(); i != e; ++i) {
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MemSetInst *memsetinst = aggrMemsets[i];
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Value *len = memsetinst->getLength();
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Value *val = memsetinst->getValue();
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convertMemSetToLoop(memsetinst, memsetinst->getDest(), len, val, Context,
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F);
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memsetinst->eraseFromParent();
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}
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return true;
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}
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FunctionPass *llvm::createLowerAggrCopies() {
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return new NVPTXLowerAggrCopies();
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}
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