#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/Pass.h"
#include "Support/StatisticReporter.h"
-static Statistic<> NumAdded("lowerrefs\t\t- New instructions added");
-
namespace {
- struct DecomposePass : public BasicBlockPass {
- const char *getPassName() const { return "Decompose Subscripting Exps"; }
+ Statistic<> NumAdded("lowerrefs\t\t- # of getelementptr instructions added");
+ class DecomposePass : public BasicBlockPass {
+ static bool decomposeArrayRef(GetElementPtrInst &GEP);
+ public:
virtual bool runOnBasicBlock(BasicBlock &BB);
-
- private:
- static void decomposeArrayRef(BasicBlock::iterator &BBI);
};
+
+ 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;
- }
+ 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 &MAI = cast<MemAccessInst>(*BBI);
- BasicBlock *BB = MAI.getParent();
- Value *LastPtr = MAI.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*> NewInsts;
-
// Process each index except the last one.
- //
- User::const_op_iterator OI = MAI.idx_begin(), OE = MAI.idx_end();
+ User::const_op_iterator OI = GEP.idx_begin(), OE = GEP.idx_end();
for (; 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<Constant>(*OI) &&
- cast<Constant>(OI->get())->isNullValue() &&
- OI->get()->getType() == Type::UIntTy;
-
- // 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*> Indices;
- const PointerType *PtrTy = cast<PointerType>(LastPtr->getType());
- if (isa<StructType>(PtrTy->getElementType())
- && !PtrTy->indexValid(*OI))
+ std::vector<Value*> Indices;
+
+ // 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));
+ }
+
Indices.push_back(*OI);
- // Get the type obtained by applying the first index.
- // It must be a structure or array.
- const Type *NextTy = MemAccessInst::getIndexedType(LastPtr->getType(),
- Indices, true);
- assert(isa<CompositeType>(NextTy));
-
- // Get a pointer to the structure or to the elements of the array.
- const Type *NextPtrTy =
- PointerType::get(isa<StructType>(NextTy) ? NextTy
- : cast<ArrayType>(NextTy)->getElementType());
-
- // Instruction 1: nextPtr1 = GetElementPtr LastPtr, Indices
- // This is not needed if the index is zero.
- if (!indexIsZero) {
- LastPtr = new GetElementPtrInst(LastPtr, Indices, "ptr1");
- NewInsts.push_back(cast<Instruction>(LastPtr));
- ++NumAdded;
- }
-
- // Instruction 2: nextPtr2 = cast nextPtr1 to NextPtrTy
- // This is not needed if the two types are identical.
- //
- if (LastPtr->getType() != NextPtrTy) {
- LastPtr = new CastInst(LastPtr, NextPtrTy, "ptr2");
- NewInsts.push_back(cast<Instruction>(LastPtr));
- ++NumAdded;
- }
+ // New Instruction: nextPtr1 = GetElementPtr LastPtr, Indices
+ LastPtr = new GetElementPtrInst(LastPtr, Indices, "ptr1", InsertPoint);
+ ++NumAdded;
}
-
- //
+
// Now create a new instruction to replace the original one
//
const PointerType *PtrTy = cast<PointerType>(LastPtr->getType());
- // First, get the final index vector. As above, we may need an initial [0].
- vector<Value*> Indices;
- if (isa<StructType>(PtrTy->getElementType())
- && !PtrTy->indexValid(*OI))
- Indices.push_back(Constant::getNullValue(Type::UIntTy));
-
+ // 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);
- Instruction *NewI = 0;
- switch(MAI.getOpcode()) {
- case Instruction::Load:
- NewI = new LoadInst(LastPtr, Indices, MAI.getName());
- break;
- case Instruction::Store:
- NewI = new StoreInst(MAI.getOperand(0), LastPtr, Indices);
- break;
- case Instruction::GetElementPtr:
- NewI = new GetElementPtrInst(LastPtr, Indices, MAI.getName());
- break;
- default:
- assert(0 && "Unrecognized memory access instruction");
- }
- NewInsts.push_back(NewI);
-
- // Replace all uses of the old instruction with the new
- MAI.replaceAllUsesWith(NewI);
+ Value *NewVal = new GetElementPtrInst(LastPtr, Indices, GEP.getName(),
+ InsertPoint);
- // Now delete the old instruction...
- delete &MAI;
+ // Replace all uses of the old instruction with the new
+ GEP.replaceAllUsesWith(NewVal);
- // Insert all of the new instructions...
- BB->getInstList().insert(BBI, NewInsts.begin(), NewInsts.end());
-
- // Advance the iterator to the instruction following the one just inserted...
- BBI = NewInsts.back();
- ++BBI;
+ // Now remove and delete the old instruction...
+ BB->getInstList().erase(&GEP);
+ return true;
}
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