//===- llvm/Transforms/DecomposeMultiDimRefs.cpp - Lower array refs to 1D -===//
//
-// DecomposeMultiDimRefs -
-// Convert multi-dimensional references consisting of any combination
-// of 2 or more array and structure indices into a sequence of
-// instructions (using getelementpr and cast) so that each instruction
-// has at most one index (except structure references,
-// which need an extra leading index of [0]).
+// DecomposeMultiDimRefs - Convert multi-dimensional references consisting of
+// any combination of 2 or more array and structure indices into a sequence of
+// instructions (using getelementpr and cast) so that each instruction has at
+// most one index (except structure references, which need an extra leading
+// index of [0]).
//
//===----------------------------------------------------------------------===//
-#include "llvm/Transforms/Scalar/DecomposeMultiDimRefs.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
+#include "llvm/Constant.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/BasicBlock.h"
-#include "llvm/Function.h"
#include "llvm/Pass.h"
+#include "Support/StatisticReporter.h"
namespace {
- struct DecomposePass : public BasicBlockPass {
- virtual bool runOnBasicBlock(BasicBlock *BB);
+ Statistic<> NumAdded("lowerrefs\t\t- # of getelementptr instructions added");
- private:
- static void decomposeArrayRef(BasicBlock::iterator &BBI);
+ class DecomposePass : public BasicBlockPass {
+ static bool decomposeArrayRef(GetElementPtrInst &GEP);
+ public:
+ virtual bool runOnBasicBlock(BasicBlock &BB);
};
+
+ RegisterOpt<DecomposePass> X("lowerrefs", "Decompose multi-dimensional "
+ "structure/array references");
}
-Pass *createDecomposeMultiDimRefsPass() {
+Pass
+*createDecomposeMultiDimRefsPass()
+{
return new DecomposePass();
}
// runOnBasicBlock - Entry point for array or structure references with multiple
// indices.
//
-bool DecomposePass::runOnBasicBlock(BasicBlock *BB) {
+bool
+DecomposePass::runOnBasicBlock(BasicBlock &BB)
+{
bool Changed = false;
-
- for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ) {
- if (MemAccessInst *MAI = dyn_cast<MemAccessInst>(*II)) {
- if (MAI->getNumOperands() > MAI->getFirstIndexOperandNumber()+1) {
- decomposeArrayRef(II);
- Changed = true;
- } else {
- ++II;
- }
- } else {
- ++II;
- }
+ for (BasicBlock::iterator II = BB.begin(); II != BB.end(); ) {
+ Instruction *I = II;
+ ++II;
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I))
+ if (GEP->getNumIndices() >= 2)
+ Changed |= decomposeArrayRef(*GEP); // always modifies II
}
-
return Changed;
}
+// For any GetElementPtrInst with 2 or more array and structure indices:
//
-// For any combination of 2 or more array and structure indices,
-// this function repeats the foll. until we have a one-dim. reference: {
-// ptr1 = getElementPtr [CompositeType-N] * lastPtr, uint firstIndex
-// ptr2 = cast [CompositeType-N] * ptr1 to [CompositeType-N] *
-// }
-// Then it replaces the original instruction with an equivalent one that
-// uses the last ptr2 generated in the loop and a single index.
-// If any index is (uint) 0, we omit the getElementPtr instruction.
+// opCode CompositeType* P, [uint|ubyte] idx1, ..., [uint|ubyte] idxN
//
-void DecomposePass::decomposeArrayRef(BasicBlock::iterator &BBI){
- MemAccessInst *memI = cast<MemAccessInst>(*BBI);
- BasicBlock* BB = memI->getParent();
- Value* lastPtr = memI->getPointerOperand();
-
- // Remove the instruction from the stream
- BB->getInstList().remove(BBI);
+// this function generates the foll sequence:
+//
+// ptr1 = getElementPtr P, idx1
+// ptr2 = getElementPtr ptr1, 0, idx2
+// ...
+// ptrN-1 = getElementPtr ptrN-2, 0, idxN-1
+// opCode ptrN-1, 0, idxN // New-MAI
+//
+// Then it replaces the original instruction with this sequence,
+// and replaces all uses of the original instruction with New-MAI.
+// If idx1 is 0, we simply omit the first getElementPtr instruction.
+//
+// On return: BBI points to the instruction after the current one
+// (whether or not *BBI was replaced).
+//
+// Return value: true if the instruction was replaced; false otherwise.
+//
+bool
+DecomposePass::decomposeArrayRef(GetElementPtrInst &GEP)
+{
+ BasicBlock *BB = GEP.getParent();
+ Value *LastPtr = GEP.getPointerOperand();
+ Instruction *InsertPoint = GEP.getNext(); // Insert before the next insn
- vector<Instruction*> newIvec;
-
// Process each index except the last one.
- //
- User::const_op_iterator OI = memI->idx_begin(), OE = memI->idx_end();
- for (; OI != OE && OI+1 != OE; ++OI) {
- assert(isa<PointerType>(lastPtr->getType()));
-
- // Check for a zero index. This will need a cast instead of
- // a getElementPtr, or it may need neither.
- bool indexIsZero = isa<ConstantUInt>(*OI) &&
- cast<Constant>(*OI)->isNullValue();
-
- // Extract the first index. If the ptr is a pointer to a structure
- // and the next index is a structure offset (i.e., not an array offset),
- // we need to include an initial [0] to index into the pointer.
- vector<Value*> idxVec(1, *OI);
- PointerType* ptrType = cast<PointerType>(lastPtr->getType());
- if (isa<StructType>(ptrType->getElementType())
- && ! ptrType->indexValid(*OI))
- idxVec.insert(idxVec.begin(), ConstantUInt::get(Type::UIntTy, 0));
-
- // Get the type obtained by applying the first index.
- // It must be a structure or array.
- const Type* nextType = MemAccessInst::getIndexedType(lastPtr->getType(),
- idxVec, true);
- assert(isa<StructType>(nextType) || isa<ArrayType>(nextType));
+ User::const_op_iterator OI = GEP.idx_begin(), OE = GEP.idx_end();
+ for (; OI+1 != OE; ++OI) {
+ std::vector<Value*> Indices;
- // Get a pointer to the structure or to the elements of the array.
- const Type* nextPtrType =
- PointerType::get(isa<StructType>(nextType) ? nextType
- : cast<ArrayType>(nextType)->getElementType());
-
- // Instruction 1: nextPtr1 = GetElementPtr lastPtr, idxVec
- // This is not needed if the index is zero.
- Value *gepValue;
- if (indexIsZero)
- gepValue = lastPtr;
- else {
- gepValue = new GetElementPtrInst(lastPtr, idxVec,"ptr1");
- newIvec.push_back(cast<Instruction>(gepValue));
- }
-
- // Instruction 2: nextPtr2 = cast nextPtr1 to nextPtrType
- // This is not needed if the two types are identical.
- Value *castInst;
- if (gepValue->getType() == nextPtrType)
- castInst = gepValue;
- else {
- castInst = new CastInst(gepValue, nextPtrType, "ptr2");
- newIvec.push_back(cast<Instruction>(castInst));
+ // If this is the first index and is 0, skip it and move on!
+ if (OI == GEP.idx_begin()) {
+ if (*OI == ConstantInt::getNullValue((*OI)->getType()))
+ continue;
+ } else {
+ // Not the first index: include initial [0] to deref the last ptr
+ Indices.push_back(Constant::getNullValue(Type::UIntTy));
}
-
- lastPtr = castInst;
+
+ Indices.push_back(*OI);
+
+ // New Instruction: nextPtr1 = GetElementPtr LastPtr, Indices
+ LastPtr = new GetElementPtrInst(LastPtr, Indices, "ptr1", InsertPoint);
+ ++NumAdded;
}
-
- //
+
// Now create a new instruction to replace the original one
//
- PointerType *ptrType = cast<PointerType>(lastPtr->getType());
-
- // First, get the final index vector. As above, we may need an initial [0].
- vector<Value*> idxVec(1, *OI);
- if (isa<StructType>(ptrType->getElementType())
- && !ptrType->indexValid(*OI))
- idxVec.insert(idxVec.begin(), Constant::getNullValue(Type::UIntTy));
-
- Instruction* newInst = NULL;
- switch(memI->getOpcode()) {
- case Instruction::Load:
- newInst = new LoadInst(lastPtr, idxVec, memI->getName());
- break;
- case Instruction::Store:
- newInst = new StoreInst(memI->getOperand(0), lastPtr, idxVec);
- break;
- case Instruction::GetElementPtr:
- newInst = new GetElementPtrInst(lastPtr, idxVec, memI->getName());
- break;
- default:
- assert(0 && "Unrecognized memory access instruction");
- }
- newIvec.push_back(newInst);
-
- // Replace all uses of the old instruction with the new
- memI->replaceAllUsesWith(newInst);
+ const PointerType *PtrTy = cast<PointerType>(LastPtr->getType());
- // Now delete the old instruction...
- delete memI;
+ // Get the final index vector, including an initial [0] as before.
+ std::vector<Value*> Indices;
+ Indices.push_back(Constant::getNullValue(Type::UIntTy));
+ Indices.push_back(*OI);
- // Convert our iterator into an index... that cannot get invalidated
- unsigned ItOffs = BBI-BB->begin();
+ Value *NewVal = new GetElementPtrInst(LastPtr, Indices, GEP.getName(),
+ InsertPoint);
+
+ // Replace all uses of the old instruction with the new
+ GEP.replaceAllUsesWith(NewVal);
- // Insert all of the new instructions...
- BB->getInstList().insert(BBI, newIvec.begin(), newIvec.end());
-
- // Advance the iterator to the instruction following the one just inserted...
- BBI = BB->begin() + (ItOffs+newIvec.size());
+ // Now remove and delete the old instruction...
+ BB->getInstList().erase(&GEP);
+ return true;
}
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