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Extract most of the transformation into an externally accessible 

function -- DecomposeArrayRef(GetElementPtrInst* GEP) -- that can
be invoked on a single instruction at a time.

llvm-svn: 3755
This commit is contained in:
Vikram S. Adve 2002-09-16 16:40:07 +00:00
parent 116783613a
commit dba59921d7
1 changed files with 31 additions and 27 deletions
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58
llvm/lib/Transforms/Scalar/DecomposeMultiDimRefs.cpp
View File

@ -21,16 +21,14 @@
namespace {
Statistic<> NumAdded("lowerrefs\t\t- # of getelementptr instructions added");
class DecomposePass : public BasicBlockPass {
static bool decomposeArrayRef(GetElementPtrInst &GEP);
public:
struct DecomposePass : public BasicBlockPass {
virtual bool runOnBasicBlock(BasicBlock &BB);
};
RegisterOpt<DecomposePass> X("lowerrefs", "Decompose multi-dimensional "
"structure/array references");
}
RegisterOpt<DecomposePass> X("lowerrefs", "Decompose multi-dimensional "
"structure/array references");
Pass
*createDecomposeMultiDimRefsPass()
{
@ -44,17 +42,17 @@ Pass
bool
DecomposePass::runOnBasicBlock(BasicBlock &BB)
{
bool Changed = false;
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;
bool changed = false;
for (BasicBlock::iterator II = BB.begin(); II != BB.end(); )
if (GetElementPtrInst *gep = dyn_cast<GetElementPtrInst>(&*II++)) // pre-inc
if (gep->getNumIndices() >= 2)
changed |= DecomposeArrayRef(gep); // always modifies II
return changed;
}
// Function: DecomposeArrayRef()
//
// For any GetElementPtrInst with 2 or more array and structure indices:
//
// opCode CompositeType* P, [uint|ubyte] idx1, ..., [uint|ubyte] idxN
@ -77,25 +75,30 @@ DecomposePass::runOnBasicBlock(BasicBlock &BB)
// Return value: true if the instruction was replaced; false otherwise.
//
bool
DecomposePass::decomposeArrayRef(GetElementPtrInst &GEP)
DecomposeArrayRef(GetElementPtrInst* GEP)
{
BasicBlock *BB = GEP.getParent();
Value *LastPtr = GEP.getPointerOperand();
Instruction *InsertPoint = GEP.getNext(); // Insert before the next insn
if (GEP->getNumIndices() < 2)
return false;
BasicBlock *BB = GEP->getParent();
Value *LastPtr = GEP->getPointerOperand();
Instruction *InsertPoint = GEP->getNext(); // Insert before the next insn
// The vector of new instructions to be created
std::vector<Instruction*> NewInsts;
// Process each index except the last one.
User::const_op_iterator OI = GEP.idx_begin(), OE = GEP.idx_end();
User::const_op_iterator OI = GEP->idx_begin(), OE = GEP->idx_end();
for (; OI+1 != OE; ++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 == 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::LongTy));
}
else // Not the first index: include initial [0] to deref the last ptr
Indices.push_back(Constant::getNullValue(Type::LongTy));
Indices.push_back(*OI);
@ -113,13 +116,14 @@ DecomposePass::decomposeArrayRef(GetElementPtrInst &GEP)
Indices.push_back(Constant::getNullValue(Type::LongTy));
Indices.push_back(*OI);
Value *NewVal = new GetElementPtrInst(LastPtr, Indices, GEP.getName(),
Value *NewVal = new GetElementPtrInst(LastPtr, Indices, GEP->getName(),
InsertPoint);
// Replace all uses of the old instruction with the new
GEP.replaceAllUsesWith(NewVal);
GEP->replaceAllUsesWith(NewVal);
// Now remove and delete the old instruction...
BB->getInstList().erase(&GEP);
BB->getInstList().erase(GEP);
return true;
}