Crash when lowering multiple dimention array

[ChuanqiXu9]

Reproducer:

// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll
// RUN: FileCheck --input-file=%t.ll %s -check-prefix=LLVM

unsigned char table[10][3] =
{
    {1,0},
    {7,6,5},
};

the interesting part is, if we change the first dimension 10 to any number lower, it won't crash.

The crash information comes from:

clangir/clang/lib/CIR/Lowering/LoweringHelpers.cpp

Lines 124 to 125 in 2ca12fe

	return mlir::DenseElementsAttr::get(mlir::RankedTensorType::get(dims, type),
	llvm::ArrayRef(values));

where the MLIR will assert the size of values will be the same with tensor. The shape of the tensor is correct. However, we will insert values to values in

clangir/clang/lib/CIR/Lowering/LoweringHelpers.cpp

Lines 79 to 115 in 2ca12fe

	template <typename AttrTy, typename StorageTy>
	void convertToDenseElementsAttrImpl(mlir::cir::ConstArrayAttr attr,
	llvm::SmallVectorImpl<StorageTy> &values) {
	if (auto stringAttr = mlir::dyn_cast<mlir::StringAttr>(attr.getElts())) {
	if (auto arrayType = mlir::dyn_cast<mlir::cir::ArrayType>(attr.getType())) {
	for (auto element : stringAttr) {
	auto intAttr = mlir::cir::IntAttr::get(arrayType.getEltType(), element);
	values.push_back(mlir::dyn_cast<AttrTy>(intAttr).getValue());
	}
	return;
	}
	}
	auto arrayAttr = mlir::cast<mlir::ArrayAttr>(attr.getElts());
	for (auto eltAttr : arrayAttr) {
	if (auto valueAttr = mlir::dyn_cast<AttrTy>(eltAttr)) {
	values.push_back(valueAttr.getValue());
	} else if (auto subArrayAttr =
	mlir::dyn_cast<mlir::cir::ConstArrayAttr>(eltAttr)) {
	convertToDenseElementsAttrImpl<AttrTy>(subArrayAttr, values);
	if (mlir::dyn_cast<mlir::StringAttr>(subArrayAttr.getElts()))
	fillTrailingZeros(subArrayAttr, values);
	} else if (auto zeroAttr = mlir::dyn_cast<mlir::cir::ZeroAttr>(eltAttr)) {
	unsigned numStoredZeros = 0;
	auto nestTy =
	getNestedTypeAndElemQuantity(zeroAttr.getType(), numStoredZeros);
	values.insert(values.end(), numStoredZeros,
	getZeroInitFromType<StorageTy>(nestTy));
	} else {
	llvm_unreachable("unknown element in ConstArrayAttr");
	}
	}
	// Only fill in trailing zeros at the local cir.array level where the element
	// type isn't another array (for the mult-dim case).
	fillTrailingZeros(attr, values);
	}

and it looks like the logics are somehow not correct so that it didn't generate values with enough elements.

I think we should resize values in the first place and assign values to the corresponding slot.