+const Type *ConvertableToGEP(const Type *Ty, Value *OffsetVal,
+ std::vector<Value*> &Indices,
+ BasicBlock::iterator *BI) {
+ const CompositeType *CompTy = dyn_cast<CompositeType>(Ty);
+ if (CompTy == 0) return 0;
+
+ // See if the cast is of an integer expression that is either a constant,
+ // or a value scaled by some amount with a possible offset.
+ //
+ ExprType Expr = ClassifyExpression(OffsetVal);
+
+ // Get the offset and scale values if they exists...
+ // A scale of zero with Expr.Var != 0 means a scale of 1.
+ //
+ int64_t Offset = Expr.Offset ? getConstantValue(Expr.Offset) : 0;
+ int64_t Scale = Expr.Scale ? getConstantValue(Expr.Scale) : 0;
+
+ if (Expr.Var && Scale == 0) Scale = 1; // Scale != 0 if Expr.Var != 0
+
+ // Loop over the Scale and Offset values, filling in the Indices vector for
+ // our final getelementptr instruction.
+ //
+ const Type *NextTy = CompTy;
+ do {
+ if (!isa<CompositeType>(NextTy))
+ return 0; // Type must not be ready for processing...
+ CompTy = cast<CompositeType>(NextTy);
+
+ if (const StructType *StructTy = dyn_cast<StructType>(CompTy)) {
+ // Step into the appropriate element of the structure...
+ uint64_t ActualOffset = (Offset < 0) ? 0 : (uint64_t)Offset;
+ NextTy = getStructOffsetStep(StructTy, ActualOffset, Indices);
+ Offset -= ActualOffset;
+ } else {
+ const Type *ElTy = cast<SequentialType>(CompTy)->getElementType();
+ if (!ElTy->isSized())
+ return 0; // Type is unreasonable... escape!
+ unsigned ElSize = TD.getTypeSize(ElTy);
+ int64_t ElSizeS = ElSize;
+
+ // See if the user is indexing into a different cell of this array...
+ if (Scale && (Scale >= ElSizeS || -Scale >= ElSizeS)) {
+ // A scale n*ElSize might occur if we are not stepping through
+ // array by one. In this case, we will have to insert math to munge
+ // the index.
+ //
+ int64_t ScaleAmt = Scale/ElSizeS;
+ if (Scale-ScaleAmt*ElSizeS)
+ return 0; // Didn't scale by a multiple of element size, bail out
+ Scale = 0; // Scale is consumed
+
+ int64_t Index = Offset/ElSize; // is zero unless Offset > ElSize
+ Offset -= Index*ElSize; // Consume part of the offset
+
+ if (BI) { // Generate code?
+ BasicBlock *BB = (*BI)->getParent();
+ if (Expr.Var->getType() != Type::LongTy)
+ Expr.Var = new CastInst(Expr.Var, Type::LongTy,
+ Expr.Var->getName()+"-idxcast", *BI);
+
+ if (ScaleAmt && ScaleAmt != 1) {
+ // If we have to scale up our index, do so now
+ Value *ScaleAmtVal = ConstantSInt::get(Type::LongTy, ScaleAmt);
+ Expr.Var = BinaryOperator::create(Instruction::Mul, Expr.Var,
+ ScaleAmtVal,
+ Expr.Var->getName()+"-scale",*BI);
+ }
+
+ if (Index) { // Add an offset to the index
+ Value *IndexAmt = ConstantSInt::get(Type::LongTy, Index);
+ Expr.Var = BinaryOperator::create(Instruction::Add, Expr.Var,
+ IndexAmt,
+ Expr.Var->getName()+"-offset",
+ *BI);
+ }
+ }
+
+ Indices.push_back(Expr.Var);
+ Expr.Var = 0;
+ } else if (Offset >= (int64_t)ElSize || -Offset >= (int64_t)ElSize) {
+ // Calculate the index that we are entering into the array cell with
+ uint64_t Index = Offset/ElSize;
+ Indices.push_back(ConstantSInt::get(Type::LongTy, Index));
+ Offset -= (int64_t)(Index*ElSize); // Consume part of the offset
+
+ } else if (isa<ArrayType>(CompTy) || Indices.empty()) {
+ // Must be indexing a small amount into the first cell of the array
+ // Just index into element zero of the array here.
+ //
+ Indices.push_back(ConstantSInt::get(Type::LongTy, 0));
+ } else {
+ return 0; // Hrm. wierd, can't handle this case. Bail
+ }
+ NextTy = ElTy;
+ }
+ } while (Offset || Scale); // Go until we're done!
+
+ return NextTy;