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Constant fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
Into: inttoptr (i64 0 to i8*) -> null This occurs in the example in PR1602. With this fixed, we now compile the example in PR1602 into fully "devirtualized" code: define void @_Z1g1S(%struct.S* noalias %s) { entry: %tmp131415 = getelementptr %struct.S* %s, i32 0, i32 0 ; <i32 (...)***> [#uses=1] %tmp16 = load i32 (...)*** %tmp131415, align 4 ; <i32 (...)**> [#uses=1] %tmp26277 = load i32 (...)** %tmp16 ; <i32 (...)*> [#uses=1] %tmp2829 = bitcast i32 (...)* %tmp26277 to void (%struct.S*)* ; <void (%struct.S*)*> [#uses=1] tail call void %tmp2829( %struct.S* %s ) ret void } This still has the vtable dispatch (as required) but does not have any pointer to method cruft left. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41046 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1427,7 +1427,7 @@ Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
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// long 0, long 0)
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// To: int* getelementptr ([3 x int]* %X, long 0, long 0)
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//
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if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue())
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if (CE->isCast() && NumIdx > 1 && Idx0->isNullValue()) {
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if (const PointerType *SPT =
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dyn_cast<PointerType>(CE->getOperand(0)->getType()))
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if (const ArrayType *SAT = dyn_cast<ArrayType>(SPT->getElementType()))
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@ -1436,6 +1436,28 @@ Constant *llvm::ConstantFoldGetElementPtr(const Constant *C,
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if (CAT->getElementType() == SAT->getElementType())
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return ConstantExpr::getGetElementPtr(
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(Constant*)CE->getOperand(0), Idxs, NumIdx);
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}
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// Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
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// Into: inttoptr (i64 0 to i8*)
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// This happens with pointers to member functions in C++.
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if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
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isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
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cast<PointerType>(CE->getType())->getElementType() == Type::Int8Ty) {
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Constant *Base = CE->getOperand(0);
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Constant *Offset = Idxs[0];
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// Convert the smaller integer to the larger type.
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if (Offset->getType()->getPrimitiveSizeInBits() <
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Base->getType()->getPrimitiveSizeInBits())
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Offset = ConstantExpr::getSExt(Offset, Base->getType());
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else if (Base->getType()->getPrimitiveSizeInBits() <
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Offset->getType()->getPrimitiveSizeInBits())
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Base = ConstantExpr::getZExt(Base, Base->getType());
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Base = ConstantExpr::getAdd(Base, Offset);
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return ConstantExpr::getIntToPtr(Base, CE->getType());
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}
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}
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return 0;
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}
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