Implement PR1795, an instcombine hack for forming GEPs with integer pointer arithmetic.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45745 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 19f86f9..93fad0a 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -210,7 +210,7 @@
Instruction *visitUIToFP(CastInst &CI);
Instruction *visitSIToFP(CastInst &CI);
Instruction *visitPtrToInt(CastInst &CI);
- Instruction *visitIntToPtr(CastInst &CI);
+ Instruction *visitIntToPtr(IntToPtrInst &CI);
Instruction *visitBitCast(BitCastInst &CI);
Instruction *FoldSelectOpOp(SelectInst &SI, Instruction *TI,
Instruction *FI);
@@ -7148,8 +7148,58 @@
return commonPointerCastTransforms(CI);
}
-Instruction *InstCombiner::visitIntToPtr(CastInst &CI) {
- return commonCastTransforms(CI);
+Instruction *InstCombiner::visitIntToPtr(IntToPtrInst &CI) {
+ if (Instruction *I = commonCastTransforms(CI))
+ return I;
+
+ const Type *DestPointee = cast<PointerType>(CI.getType())->getElementType();
+ if (!DestPointee->isSized()) return 0;
+
+ // If this is inttoptr(add (ptrtoint x), cst), try to turn this into a GEP.
+ ConstantInt *Cst;
+ Value *X;
+ if (match(CI.getOperand(0), m_Add(m_Cast<PtrToIntInst>(m_Value(X)),
+ m_ConstantInt(Cst)))) {
+ // If the source and destination operands have the same type, see if this
+ // is a single-index GEP.
+ if (X->getType() == CI.getType()) {
+ // Get the size of the pointee type.
+ uint64_t Size = TD->getABITypeSizeInBits(DestPointee);
+
+ // Convert the constant to intptr type.
+ APInt Offset = Cst->getValue();
+ Offset.sextOrTrunc(TD->getPointerSizeInBits());
+
+ // If Offset is evenly divisible by Size, we can do this xform.
+ if (Size && !APIntOps::srem(Offset, APInt(Offset.getBitWidth(), Size))){
+ Offset = APIntOps::sdiv(Offset, APInt(Offset.getBitWidth(), Size));
+ return new GetElementPtrInst(X, ConstantInt::get(Offset));
+ }
+ }
+ // TODO: Could handle other cases, e.g. where add is indexing into field of
+ // struct etc.
+ } else if (CI.getOperand(0)->hasOneUse() &&
+ match(CI.getOperand(0), m_Add(m_Value(X), m_ConstantInt(Cst)))) {
+ // Otherwise, if this is inttoptr(add x, cst), try to turn this into an
+ // "inttoptr+GEP" instead of "add+intptr".
+
+ // Get the size of the pointee type.
+ uint64_t Size = TD->getABITypeSize(DestPointee);
+
+ // Convert the constant to intptr type.
+ APInt Offset = Cst->getValue();
+ Offset.sextOrTrunc(TD->getPointerSizeInBits());
+
+ // If Offset is evenly divisible by Size, we can do this xform.
+ if (Size && !APIntOps::srem(Offset, APInt(Offset.getBitWidth(), Size))){
+ Offset = APIntOps::sdiv(Offset, APInt(Offset.getBitWidth(), Size));
+
+ Instruction *P = InsertNewInstBefore(new IntToPtrInst(X, CI.getType(),
+ "tmp"), CI);
+ return new GetElementPtrInst(P, ConstantInt::get(Offset), "tmp");
+ }
+ }
+ return 0;
}
Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {