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Major overhaul to support arbitrary mixed array and structure indices.

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Also moved to the Scalar/ directory and renamed to "MultiDim".


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@1961 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Vikram S. Adve 2002-03-24 03:21:18 +00:00
parent d32e70a09f
commit 98d64f8d51
2 changed files with 103 additions and 70 deletions
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16
include/llvm/Transforms/Scalar/DecomposeMultiDimRefs.h
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@ -1,16 +1,18 @@
//===- llvm/Transforms/DecomposeArrayRefs.h - Lower array refs --*- C++ -*--=//
//===- llvm/Transforms/DecomposeMultiDimRefs.h - Lower multi-dim refs --*- C++ -*--=//
//
// DecomposeArrayRefs -
// Convert multi-dimensional array references into a sequence of
// 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 array offset.
// has at most one index (except structure references,
// which need an extra leading index of [0]).
//
//===---------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_DECOMPOSEARRAYREFS_H
#define LLVM_TRANSFORMS_DECOMPOSEARRAYREFS_H
#ifndef LLVM_TRANSFORMS_SCALAR_DECOMPOSEMULTIDIMREFS_H
#define LLVM_TRANSFORMS_SCALAR_DECOMPOSEMULTIDIMREFS_H
class Pass;
Pass *createDecomposeArrayRefsPass();
Pass *createDecomposeMultiDimRefsPass();
#endif

157
lib/Transforms/Scalar/DecomposeMultiDimRefs.cpp
View File

@ -1,13 +1,16 @@
//===- llvm/Transforms/DecomposeArrayRefs.cpp - Lower array refs to 1D -----=//
//===- llvm/Transforms/DecomposeMultiDimRefs.cpp - Lower array refs to 1D -----=//
//
// DecomposeArrayRefs -
// Convert multi-dimensional array references into a sequence of
// 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 array offset.
// has at most one index (except structure references,
// which need an extra leading index of [0]).
//
//===---------------------------------------------------------------------===//
#include "llvm/Transforms/DecomposeArrayRefs.h"
#include "llvm/Transforms/Scalar/DecomposeMultiDimRefs.h"
#include "llvm/ConstantVals.h"
#include "llvm/iMemory.h"
#include "llvm/iOther.h"
#include "llvm/BasicBlock.h"
@ -16,61 +19,98 @@
//
// This function repeats until we have a one-dim. reference: {
// // For an N-dim array ref, where N > 1, insert:
// aptr1 = getElementPtr [N-dim array] * lastPtr, uint firstIndex
// aptr2 = cast [N-dim-arry] * aptr to [<N-1>-dim-array] *
// 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 aptr2 generated in the loop and a single index.
// uses the last ptr2 generated in the loop and a single index.
// If any index is (uint) 0, we omit the getElementPtr instruction.
//
static BasicBlock::reverse_iterator
decomposeArrayRef(BasicBlock::reverse_iterator& BBI)
static BasicBlock::iterator
decomposeArrayRef(BasicBlock::iterator& BBI)
{
MemAccessInst *memI = cast<MemAccessInst>(*BBI);
BasicBlock* BB = memI->getParent();
Value* lastPtr = memI->getPointerOperand();
vector<Instruction*> newIvec;
// Process each index except the last one.
//
MemAccessInst::const_op_iterator OI = memI->idx_begin();
for (MemAccessInst::const_op_iterator OE = memI->idx_end(); OI != OE; ++OI)
MemAccessInst::const_op_iterator OE = memI->idx_end();
for ( ; OI != OE; ++OI)
{
if (OI+1 == OE) // skip the last operand
assert(isa<PointerType>(lastPtr->getType()));
if (OI+1 == OE) // stop before the last operand
break;
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 = bool(isa<ConstantUInt>(*OI) &&
cast<ConstantUInt>(*OI)->getValue() == 0);
// 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);
// The first index does not change the type of the pointer
// since all pointers are treated as potential arrays (i.e.,
// int *X is either a scalar X[0] or an array at X[i]).
//
const Type* nextPtrType;
// if (OI == memI->idx_begin())
// nextPtrType = lastPtr->getType();
// else
// {
const Type* nextArrayType =
MemAccessInst::getIndexedType(lastPtr->getType(), idxVec,
/*allowCompositeLeaf*/ true);
nextPtrType = PointerType::get(cast<SequentialType>(nextArrayType)
->getElementType());
// }
PointerType* ptrType = cast<PointerType>(lastPtr->getType());
if (isa<StructType>(ptrType->getElementType())
&& ! ptrType->indexValid(*OI))
idxVec.insert(idxVec.begin(), ConstantUInt::get(Type::UIntTy, 0));
Instruction* gepInst = new GetElementPtrInst(lastPtr, idxVec, "aptr1");
Instruction* castInst = new CastInst(gepInst, nextPtrType, "aptr2");
lastPtr = castInst;
// 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));
newIvec.push_back(gepInst);
newIvec.push_back(castInst);
// 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));
}
lastPtr = castInst;
}
//
// Now create a new instruction to replace the original one
assert(lastPtr != memI->getPointerOperand() && "the above loop did not execute?");
assert(isa<PointerType>(lastPtr->getType()));
//
PointerType* ptrType = cast<PointerType>(lastPtr->getType());
assert(ptrType);
// 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(), ConstantUInt::get(Type::UIntTy, 0));
const std::string newInstName = memI->hasName()? memI->getName()
: string("oneDimRef");
: string("finalRef");
Instruction* newInst = NULL;
switch(memI->getOpcode())
@ -92,47 +132,38 @@ decomposeArrayRef(BasicBlock::reverse_iterator& BBI)
// Replace all uses of the old instruction with the new
memI->replaceAllUsesWith(newInst);
// Insert the instructions created in reverse order. insert is destructive
// so we always have to use the new pointer returned by insert.
BasicBlock::iterator newI = BBI.base(); // gives ptr to instr. after memI
--newI; // step back to memI
BasicBlock::iterator newI = BBI;;
for (int i = newIvec.size()-1; i >= 0; i--)
newI = BB->getInstList().insert(newI, newIvec[i]);
// Now delete the old instruction and return a pointer to the first new one
// Now delete the old instruction and return a pointer to the last new one
BB->getInstList().remove(memI);
delete memI;
BasicBlock::reverse_iterator retI(newI); // reverse ptr to instr before newI
return --retI; // reverse pointer to newI
return newI + newIvec.size() - 1; // pointer to last new instr
}
//---------------------------------------------------------------------------
// Entry point for decomposing multi-dimensional array references
// Entry point for array or structure references with multiple indices.
//---------------------------------------------------------------------------
static bool
doDecomposeArrayRefs(Method *M)
doDecomposeMultiDimRefs(Method *M)
{
bool changed = false;
for (Method::iterator BI = M->begin(), BE = M->end(); BI != BE; ++BI)
for (BasicBlock::reverse_iterator newI, II=(*BI)->rbegin();
II != (*BI)->rend(); II = ++newI)
for (BasicBlock::iterator newI, II=(*BI)->begin();
II != (*BI)->end(); II = ++newI)
{
newI = II;
if (MemAccessInst *memI = dyn_cast<MemAccessInst>(*II))
{ // Check for a multi-dimensional array access
const PointerType* ptrType =
cast<PointerType>(memI->getPointerOperand()->getType());
if (isa<ArrayType>(ptrType->getElementType()) &&
memI->getNumOperands() > 1+ memI->getFirstIndexOperandNumber())
{
newI = decomposeArrayRef(II);
changed = true;
}
}
if (memI->getNumOperands() > 1 + memI->getFirstIndexOperandNumber())
{
newI = decomposeArrayRef(II);
changed = true;
}
}
return changed;
@ -140,9 +171,9 @@ doDecomposeArrayRefs(Method *M)
namespace {
struct DecomposeArrayRefsPass : public MethodPass {
virtual bool runOnMethod(Method *M) { return doDecomposeArrayRefs(M); }
struct DecomposeMultiDimRefsPass : public MethodPass {
virtual bool runOnMethod(Method *M) { return doDecomposeMultiDimRefs(M); }
};
}
Pass *createDecomposeArrayRefsPass() { return new DecomposeArrayRefsPass(); }
Pass *createDecomposeMultiDimRefsPass() { return new DecomposeMultiDimRefsPass(); }