backend: refine load store optimization

this fix basic test in conformance tests failed for vec8 of char because
of overflow. And it fix many test items failed in opencv because of offset error

(1)modify the size of searchInsnArray to 32, it is the max size for char
   And add check for overflow if too many insn
(2)Make sure the start insn is the first insn of searched array
   because if it is not the first, the offset maybe invalid. And
   it is complex to modify offset without error

V2: refine search index, using J not I
V3: remove (2), now add offset to the pointer of start
    pass OpenCV, conformance basic and compiler tests, utests
V4: check pointer type, if 64bit, modify it by 64, or 32
V5: refine findSafeInstruction() and variable naming in
    findConsecutiveAccess().

Signed-off-by: rander.wang <rander.wang@intel.com>
Signed-off-by: Ruiling Song <ruiling.song@intel.com>
Reviewed-by: Yang Rong <rong.r.yang@intel.com>

1 files changed, 88 insertions, 37 deletions

diff --git a/backend/src/llvm/llvm_loadstore_optimization.cpp b/backend/src/llvm/llvm_loadstore_optimization.cpp
index c91c1a03..bb8dc5f6 100644
--- a/backend/src/llvm/llvm_loadstore_optimization.cpp
+++ b/backend/src/llvm/llvm_loadstore_optimization.cpp
@@ -68,13 +68,14 @@ namespace gbe {
     bool     optimizeLoadStore(BasicBlock &BB);
 
     bool     isLoadStoreCompatible(Value *A, Value *B, int *dist, int* elementSize, int maxVecSize);
-    void     mergeLoad(BasicBlock &BB, SmallVector<Instruction*, 16> &merged);
-    void     mergeStore(BasicBlock &BB, SmallVector<Instruction*, 16> &merged);
+    void     mergeLoad(BasicBlock &BB, SmallVector<Instruction*, 16> &merged, Instruction *start,int offset);
+    void     mergeStore(BasicBlock &BB, SmallVector<Instruction*, 16> &merged, Instruction *start,int offset);
     bool     findConsecutiveAccess(BasicBlock &BB,
                                   SmallVector<Instruction*, 16> &merged,
                                   const BasicBlock::iterator &start,
                                   unsigned maxVecSize,
-                                  bool isLoad);
+                                  bool isLoad,
+                                  int *addrOffset);
 #if LLVM_VERSION_MAJOR * 10 + LLVM_VERSION_MINOR >= 40
     virtual StringRef getPassName() const
 #else
@@ -143,7 +144,10 @@ namespace gbe {
     return (abs(-offset) < sz*maxVecSize);
   }
 
-  void GenLoadStoreOptimization::mergeLoad(BasicBlock &BB, SmallVector<Instruction*, 16> &merged) {
+  void GenLoadStoreOptimization::mergeLoad(BasicBlock &BB,
+                                            SmallVector<Instruction*, 16> &merged,
+                                            Instruction *start,
+                                            int offset) {
     IRBuilder<> Builder(&BB);
 
     unsigned size = merged.size();
@@ -151,14 +155,27 @@ namespace gbe {
     for(unsigned i = 0; i < size; i++) {
       values.push_back(merged[i]);
     }
-    LoadInst *ld = cast<LoadInst>(merged[0]);
+    LoadInst *ld = cast<LoadInst>(start);
     unsigned align = ld->getAlignment();
     unsigned addrSpace = ld->getPointerAddressSpace();
     // insert before first load
     Builder.SetInsertPoint(ld);
+
+    //modify offset
+    Value *newPtr = ld->getPointerOperand();
+    if(offset != 0)
+    {
+      Type *ptype = ld->getPointerOperand()->getType();
+      unsigned typeSize = TD->getPointerTypeSize(ptype);
+      ptype = (typeSize == 4) ? Builder.getInt32Ty():Builder.getInt64Ty();
+      Value *StartAddr = Builder.CreatePtrToInt(ld->getPointerOperand(), ptype);
+      Value *offsetVal = ConstantInt::get(ptype, offset);
+      Value *newAddr = Builder.CreateAdd(StartAddr, offsetVal);
+      newPtr = Builder.CreateIntToPtr(newAddr, ld->getPointerOperand()->getType());
+    }
+
     VectorType *vecTy = VectorType::get(ld->getType(), size);
-    Value *vecPtr = Builder.CreateBitCast(ld->getPointerOperand(),
-                                        PointerType::get(vecTy, addrSpace));
+    Value *vecPtr = Builder.CreateBitCast(newPtr, PointerType::get(vecTy, addrSpace));
     LoadInst *vecValue = Builder.CreateLoad(vecPtr);
     vecValue->setAlignment(align);
 
@@ -196,8 +213,8 @@ namespace gbe {
                             SmallVector<Instruction*, 16> &merged,
                             const BasicBlock::iterator &start,
                             unsigned maxVecSize,
-                            bool isLoad) {
-
+                            bool isLoad,
+                            int *addrOffset) {
     if(!isSimpleLoadStore(&*start)) return false;
 
     unsigned targetAddrSpace = getAddressSpace(&*start);
@@ -207,35 +224,40 @@ namespace gbe {
     ++J;
 
     unsigned maxLimit = maxVecSize * 8;
-    bool reordered = false;
-
+    bool crossAddressSpace = false;
+    // When we are merging loads and there are some other AddressSpace stores
+    // lies among them, we are saying that loadStoreReorder happens. The same
+    // for merging stores and there are some other AddressSpace load among them.
+    bool loadStoreReorder = false;
     bool ready = false;
     int elementSize;
 
-    SmallVector<mergedInfo *, 16> searchInsnArray;
-    mergedInfo meInfoArray[16];
+    SmallVector<mergedInfo *, 32> searchInsnArray;
+    mergedInfo meInfoArray[32];
     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<LoadInst>(*I)) || (!isLoad && isa<StoreInst>(*J))) {
+    for(unsigned ss = 0; J!= E && ss <= maxLimit; ++ss, ++J) {
+      if((isLoad && isa<LoadInst>(*J)) || (!isLoad && isa<StoreInst>(*J))) {
           int distance;
-          if(isLoadStoreCompatible(searchInsnArray[0]->mInsn, &*I, &distance, &elementSize, maxVecSize))
+          if(isLoadStoreCompatible(searchInsnArray[0]->mInsn, &*J, &distance, &elementSize, maxVecSize))
           {
-            meInfoArray[indx].init(&*I, distance);
+            meInfoArray[indx].init(&*J, distance);
             searchInsnArray.push_back(&meInfoArray[indx]);
             indx++;
+            if (crossAddressSpace)
+              loadStoreReorder = true;
+
+            if(indx >= 32)
+              break;
           }
       } else if((isLoad && isa<StoreInst>(*J))) {
         // simple stop to keep read/write order
         StoreInst *st = cast<StoreInst>(&*J);
         unsigned addrSpace = st->getPointerAddressSpace();
         if (addrSpace != targetAddrSpace) {
-          reordered = true;
+          crossAddressSpace = true;
         } else {
           break;
         }
@@ -243,15 +265,14 @@ namespace gbe {
         LoadInst *ld = cast<LoadInst>(&*J);
         unsigned addrSpace = ld->getPointerAddressSpace();
         if (addrSpace != targetAddrSpace) {
-          reordered = true;
+          crossAddressSpace = true;
         } else {
           break;
         }
       }
-
-      if(merged.size() >= maxVecSize) break;
     }
 
+
     if(indx > 1)
     {
       //try to sort the load/store by the offset from the start
@@ -275,18 +296,29 @@ namespace gbe {
 
         if(j > 0 && ready)
         {
-          for(unsigned k = 0; k < j+1; k++)
+          unsigned endIndx = j + 1;
+          *addrOffset = searchInsnArray[i]->mOffset;
+          endIndx = (endIndx >= 16) ? 16 : (endIndx >= 8 ? 8 : (endIndx >= 4 ? 4 : endIndx));
+
+          for(unsigned k = 0; k < endIndx; k++)
+          {
             merged.push_back(searchInsnArray[i+k]->mInsn);
+            if (k >= maxVecSize)
+              break;
+          }
 
           break;
         }
       }
     }
 
-    return reordered;
+    return loadStoreReorder;
   }
 
-  void GenLoadStoreOptimization::mergeStore(BasicBlock &BB, SmallVector<Instruction*, 16> &merged) {
+  void GenLoadStoreOptimization::mergeStore(BasicBlock &BB,
+                                            SmallVector<Instruction*, 16> &merged,
+                                            Instruction *start,
+                                            int offset) {
     IRBuilder<> Builder(&BB);
 
     unsigned size = merged.size();
@@ -294,7 +326,7 @@ namespace gbe {
     for(unsigned i = 0; i < size; i++) {
       values.push_back(cast<StoreInst>(merged[i])->getValueOperand());
     }
-    StoreInst *st = cast<StoreInst>(merged[0]);
+    StoreInst *st = cast<StoreInst>(start);
     if(!st)
       return;
 
@@ -314,12 +346,26 @@ namespace gbe {
     Value * stPointer = st->getPointerOperand();
     if(!stPointer)
       return;
-    Value *newPtr = Builder.CreateBitCast(stPointer, PointerType::get(vecTy, addrSpace));
+
+    //modify offset
+    Value *newSPtr = stPointer;
+    if(offset != 0)
+    {
+      unsigned typeSize = TD->getPointerTypeSize(stPointer->getType());
+      Type *ptype = (typeSize == 4) ? Builder.getInt32Ty() : Builder.getInt64Ty();
+      Value *StartAddr = Builder.CreatePtrToInt(stPointer, ptype);
+      Value *offsetVal = ConstantInt::get(ptype, offset);
+      Value *newAddr = Builder.CreateAdd(StartAddr, offsetVal);
+      newSPtr = Builder.CreateIntToPtr(newAddr, stPointer->getType());
+    }
+
+    Value *newPtr = Builder.CreateBitCast(newSPtr, PointerType::get(vecTy, addrSpace));
     StoreInst *newST = Builder.CreateStore(parent, newPtr);
     newST->setAlignment(align);
   }
 
-  // Find the safe iterator we can point to. If reorder happens, we need to
+  // Find the safe iterator (will not be deleted after the merge) we can
+  // point to. If reorder happens, we need to
   // point to the instruction after the first of toBeDeleted. If no reorder,
   // we are safe to point to the instruction after the last of toBeDeleted
   static BasicBlock::iterator
@@ -329,12 +375,15 @@ namespace gbe {
     BasicBlock::iterator safe = current;
     unsigned size = toBeDeleted.size();
     if (reorder) {
-      unsigned i = 0;
-      while (i < size && toBeDeleted[i] == &*safe) {
-        ++i;
-        ++safe;
+      BasicBlock *BB = &*current->getParent();
+      for (; safe != BB->end(); ++safe) {
+        if (std::find(toBeDeleted.begin(), toBeDeleted.end(), &*safe) ==
+            toBeDeleted.end())
+          break;
       }
     } else {
+      // TODO we should use the furthest instruction, so that the outer loop
+      // ends quicker.
       safe = BasicBlock::iterator(toBeDeleted[size - 1]);
       ++safe;
     }
@@ -355,12 +404,14 @@ namespace gbe {
              ((ty->isIntegerTy(8) || ty->isIntegerTy(16)) && isLoad)))
           continue;
 
+        int addrOffset = 0;
         unsigned maxVecSize = (ty->isFloatTy() || ty->isIntegerTy(32)) ? 4 :
                               (ty->isIntegerTy(16) ? 8 : 16);
-        bool reorder = findConsecutiveAccess(BB, merged, BBI, maxVecSize, isLoad);
+        bool reorder = findConsecutiveAccess(BB, merged, BBI, maxVecSize, isLoad, &addrOffset);
         uint32_t size = merged.size();
         uint32_t pos = 0;
         bool doDeleting = size > 1;
+        BasicBlock::iterator startLS = BBI;
         if (doDeleting) {
           // choose next undeleted instruction
           BBI = findSafeInstruction(merged, BBI, reorder);
@@ -372,9 +423,9 @@ namespace gbe {
                              (size >= 4 ? 4 : size));
           SmallVector<Instruction*, 16> mergedVec(merged.begin() + pos, merged.begin() + pos + vecSize);
           if(isLoad)
-            mergeLoad(BB, mergedVec);
+            mergeLoad(BB, mergedVec, &*startLS, addrOffset);
           else
-            mergeStore(BB, mergedVec);
+            mergeStore(BB, mergedVec, &*startLS, addrOffset);
           // remove merged insn
           for(uint32_t i = 0; i < mergedVec.size(); i++)
             mergedVec[i]->eraseFromParent();