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class. The Method class is obsolete (renamed) and all references to it are being converted over to Function. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2144 91177308-0d34-0410-b5e6-96231b3b80d8
180 lines
6.4 KiB
C++
180 lines
6.4 KiB
C++
//===- llvm/Transforms/DecomposeMultiDimRefs.cpp - Lower array refs to 1D -----=//
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//
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// DecomposeMultiDimRefs -
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// Convert multi-dimensional references consisting of any combination
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// of 2 or more array and structure indices into a sequence of
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// instructions (using getelementpr and cast) so that each instruction
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// has at most one index (except structure references,
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// which need an extra leading index of [0]).
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//
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//===---------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar/DecomposeMultiDimRefs.h"
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#include "llvm/ConstantVals.h"
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#include "llvm/iMemory.h"
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#include "llvm/iOther.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Function.h"
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#include "llvm/Pass.h"
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//
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// For any combination of 2 or more array and structure indices,
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// this function repeats the foll. until we have a one-dim. reference: {
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// ptr1 = getElementPtr [CompositeType-N] * lastPtr, uint firstIndex
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// ptr2 = cast [CompositeType-N] * ptr1 to [CompositeType-N] *
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// }
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// Then it replaces the original instruction with an equivalent one that
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// uses the last ptr2 generated in the loop and a single index.
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// If any index is (uint) 0, we omit the getElementPtr instruction.
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//
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static BasicBlock::iterator
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decomposeArrayRef(BasicBlock::iterator& BBI)
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{
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MemAccessInst *memI = cast<MemAccessInst>(*BBI);
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BasicBlock* BB = memI->getParent();
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Value* lastPtr = memI->getPointerOperand();
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vector<Instruction*> newIvec;
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// Process each index except the last one.
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//
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MemAccessInst::const_op_iterator OI = memI->idx_begin();
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MemAccessInst::const_op_iterator OE = memI->idx_end();
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for ( ; OI != OE; ++OI)
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{
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assert(isa<PointerType>(lastPtr->getType()));
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if (OI+1 == OE) // stop before the last operand
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break;
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// Check for a zero index. This will need a cast instead of
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// a getElementPtr, or it may need neither.
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bool indexIsZero = bool(isa<ConstantUInt>(*OI) &&
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cast<ConstantUInt>(*OI)->getValue() == 0);
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// Extract the first index. If the ptr is a pointer to a structure
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// and the next index is a structure offset (i.e., not an array offset),
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// we need to include an initial [0] to index into the pointer.
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vector<Value*> idxVec(1, *OI);
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PointerType* ptrType = cast<PointerType>(lastPtr->getType());
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if (isa<StructType>(ptrType->getElementType())
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&& ! ptrType->indexValid(*OI))
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idxVec.insert(idxVec.begin(), ConstantUInt::get(Type::UIntTy, 0));
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// Get the type obtained by applying the first index.
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// It must be a structure or array.
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const Type* nextType = MemAccessInst::getIndexedType(lastPtr->getType(),
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idxVec, true);
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assert(isa<StructType>(nextType) || isa<ArrayType>(nextType));
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// Get a pointer to the structure or to the elements of the array.
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const Type* nextPtrType =
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PointerType::get(isa<StructType>(nextType)? nextType
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: cast<ArrayType>(nextType)->getElementType());
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// Instruction 1: nextPtr1 = GetElementPtr lastPtr, idxVec
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// This is not needed if the index is zero.
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Value* gepValue;
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if (indexIsZero)
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gepValue = lastPtr;
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else
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{
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gepValue = new GetElementPtrInst(lastPtr, idxVec,"ptr1");
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newIvec.push_back(cast<Instruction>(gepValue));
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}
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// Instruction 2: nextPtr2 = cast nextPtr1 to nextPtrType
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// This is not needed if the two types are identical.
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Value* castInst;
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if (gepValue->getType() == nextPtrType)
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castInst = gepValue;
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else
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{
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castInst = new CastInst(gepValue, nextPtrType, "ptr2");
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newIvec.push_back(cast<Instruction>(castInst));
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}
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lastPtr = castInst;
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}
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//
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// Now create a new instruction to replace the original one
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//
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PointerType* ptrType = cast<PointerType>(lastPtr->getType());
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assert(ptrType);
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// First, get the final index vector. As above, we may need an initial [0].
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vector<Value*> idxVec(1, *OI);
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if (isa<StructType>(ptrType->getElementType())
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&& ! ptrType->indexValid(*OI))
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idxVec.insert(idxVec.begin(), ConstantUInt::get(Type::UIntTy, 0));
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const std::string newInstName = memI->hasName()? memI->getName()
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: string("finalRef");
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Instruction* newInst = NULL;
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switch(memI->getOpcode())
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{
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case Instruction::Load:
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newInst = new LoadInst(lastPtr, idxVec /*, newInstName */); break;
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case Instruction::Store:
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newInst = new StoreInst(memI->getOperand(0),
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lastPtr, idxVec /*, newInstName */); break;
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break;
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case Instruction::GetElementPtr:
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newInst = new GetElementPtrInst(lastPtr, idxVec /*, newInstName */); break;
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default:
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assert(0 && "Unrecognized memory access instruction"); break;
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}
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newIvec.push_back(newInst);
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// Replace all uses of the old instruction with the new
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memI->replaceAllUsesWith(newInst);
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BasicBlock::iterator newI = BBI;;
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for (int i = newIvec.size()-1; i >= 0; i--)
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newI = BB->getInstList().insert(newI, newIvec[i]);
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// Now delete the old instruction and return a pointer to the last new one
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BB->getInstList().remove(memI);
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delete memI;
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return newI + newIvec.size() - 1; // pointer to last new instr
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}
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//---------------------------------------------------------------------------
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// Entry point for array or structure references with multiple indices.
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//---------------------------------------------------------------------------
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static bool
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doDecomposeMultiDimRefs(Function *F)
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{
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bool changed = false;
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for (Method::iterator BI = F->begin(), BE = F->end(); BI != BE; ++BI)
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for (BasicBlock::iterator newI, II = (*BI)->begin();
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II != (*BI)->end(); II = ++newI)
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{
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newI = II;
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if (MemAccessInst *memI = dyn_cast<MemAccessInst>(*II))
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if (memI->getNumOperands() > 1 + memI->getFirstIndexOperandNumber())
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{
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newI = decomposeArrayRef(II);
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changed = true;
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}
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}
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return changed;
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}
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namespace {
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struct DecomposeMultiDimRefsPass : public MethodPass {
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virtual bool runOnMethod(Function *F) { return doDecomposeMultiDimRefs(F); }
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};
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}
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Pass *createDecomposeMultiDimRefsPass() { return new DecomposeMultiDimRefsPass(); }
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