From f0c3b352c3da283aaf4199136894b1da352832f7 Mon Sep 17 00:00:00 2001 From: rander Date: Fri, 16 Jun 2017 09:50:27 +0800 Subject: backend: refine load/store merging algorithm Now it works for sequence: load(0), load(1), load(2) but it cant work for load(2), load(0), load(1). because it compared the last merged load and the new one not all the loads for sequence: load(0), load(1), load(2). the load(0) is the start, can find that load(1) is successor without space, so put it to a merge fifo. then the start is moving to the top of fifo load(1), and compared with load(2). Also load(2) can be merged for load(2), load(0), load(1). load(2) cant be merged with load(0) for a space between them. So skip load(0) and mov to next load(1).And this load(1) can be merged. But it never go back merge load(0) Now change the algorithm. (1) find all loads maybe merged arround the start by the distance to the start. the distance is depended on data type, for 32bit data, the distance is 4. Put them in a list (2) sort the list by the distance from the start. (3) search the continuous sequence including the start to merge V2: (1)refine the sort and compare algoritm. First find all the IO in small offset compared to start. Then call std:sort (2)check the number of candidate IO to be favorable to performance for most cases there is no chance to merge IO Signed-off-by: rander.wang Reviewed-by: Ruiling Song --- backend/src/llvm/llvm_loadstore_optimization.cpp | 87 +++++++++++++++++++++--- 1 file changed, 78 insertions(+), 9 deletions(-) diff --git a/backend/src/llvm/llvm_loadstore_optimization.cpp b/backend/src/llvm/llvm_loadstore_optimization.cpp index 5aa38bef..c91c1a03 100644 --- a/backend/src/llvm/llvm_loadstore_optimization.cpp +++ b/backend/src/llvm/llvm_loadstore_optimization.cpp @@ -67,7 +67,7 @@ namespace gbe { bool isSimpleLoadStore(Value *I); bool optimizeLoadStore(BasicBlock &BB); - bool isLoadStoreCompatible(Value *A, Value *B); + bool isLoadStoreCompatible(Value *A, Value *B, int *dist, int* elementSize, int maxVecSize); void mergeLoad(BasicBlock &BB, SmallVector &merged); void mergeStore(BasicBlock &BB, SmallVector &merged); bool findConsecutiveAccess(BasicBlock &BB, @@ -109,7 +109,7 @@ namespace gbe { return NULL; } - bool GenLoadStoreOptimization::isLoadStoreCompatible(Value *A, Value *B) { + bool GenLoadStoreOptimization::isLoadStoreCompatible(Value *A, Value *B, int *dist, int* elementSize, int maxVecSize) { Value *ptrA = getPointerOperand(A); Value *ptrB = getPointerOperand(B); unsigned ASA = getAddressSpace(A); @@ -136,7 +136,11 @@ namespace gbe { // The Instructions are connsecutive if the size of the first load/store is // the same as the offset. int64_t sz = TD->getTypeStoreSize(Ty); - return ((-offset) == sz); + *dist = -offset; + *elementSize = sz; + + //a insn with small distance from the search load/store is a candidate one + return (abs(-offset) < sz*maxVecSize); } void GenLoadStoreOptimization::mergeLoad(BasicBlock &BB, SmallVector &merged) { @@ -163,6 +167,25 @@ namespace gbe { values[i]->replaceAllUsesWith(S); } } + + class mergedInfo{ + public: + Instruction* mInsn; + int mOffset; + + void init(Instruction* insn, int offset) + { + mInsn = insn; + mOffset = offset; + } + }; + + struct offsetSorter { + bool operator()(mergedInfo* m0, mergedInfo* m1) const { + return m0->mOffset < m1->mOffset; + } + }; + // When searching for consecutive memory access, we do it in a small window, // if the window is too large, it would take up too much compiling time. // An Important rule we have followed is don't try to change load/store order. @@ -177,7 +200,6 @@ namespace gbe { if(!isSimpleLoadStore(&*start)) return false; - merged.push_back(&*start); unsigned targetAddrSpace = getAddressSpace(&*start); BasicBlock::iterator E = BB.end(); @@ -187,11 +209,27 @@ namespace gbe { unsigned maxLimit = maxVecSize * 8; bool reordered = false; - for(unsigned ss = 0; J != E && ss <= maxLimit; ++ss, ++J) { - if((isLoad && isa(*J)) || (!isLoad && isa(*J))) { - if(isLoadStoreCompatible(merged[merged.size()-1], &*J)) { - merged.push_back(&*J); - } + bool ready = false; + int elementSize; + + SmallVector searchInsnArray; + mergedInfo meInfoArray[16]; + int indx = 0; + meInfoArray[indx++].init(&*start, 0); + + searchInsnArray.push_back(&meInfoArray[0]); + BasicBlock::iterator I = start; + ++I; + + for(unsigned ss = 0; I!= E && ss <= maxLimit; ++ss, ++I) { + if((isLoad && isa(*I)) || (!isLoad && isa(*J))) { + int distance; + if(isLoadStoreCompatible(searchInsnArray[0]->mInsn, &*I, &distance, &elementSize, maxVecSize)) + { + meInfoArray[indx].init(&*I, distance); + searchInsnArray.push_back(&meInfoArray[indx]); + indx++; + } } else if((isLoad && isa(*J))) { // simple stop to keep read/write order StoreInst *st = cast(&*J); @@ -214,6 +252,37 @@ namespace gbe { if(merged.size() >= maxVecSize) break; } + if(indx > 1) + { + //try to sort the load/store by the offset from the start + //the farthest is at the beginning. this is easy to find the + //continuous load/store + std::sort(searchInsnArray.begin(), searchInsnArray.end(), offsetSorter()); + + // try to find continuous loadstore insn in the candidate array + for(unsigned i = 0; i < searchInsnArray.size(); i++) + { + unsigned j; + for(j = 0; j < maxVecSize-1 && (j+i+1) < searchInsnArray.size(); j++) + { + if(searchInsnArray[i+j+1]->mOffset - searchInsnArray[i+j]->mOffset != elementSize) + break; + + //this means the search load/store which offset is 0, is in the sequence + if(searchInsnArray[i+j]->mOffset == 0 || searchInsnArray[i+j+1]->mOffset == 0) + ready = true; + } + + if(j > 0 && ready) + { + for(unsigned k = 0; k < j+1; k++) + merged.push_back(searchInsnArray[i+k]->mInsn); + + break; + } + } + } + return reordered; } -- cgit v1.2.3