This reverts commit 178b64e75bb39debc235e8008686b7c4af444013.

The author misread the report of the failure, and thought that it broke
the CI again. Reland the fix.

This reverts commit 07a534160a7c500cb71425344cca223cadd9b938.

Below is the original commit description. Furthermore, it applies a
[fix](https://github.com/llvm/llvm-project/commit/33a26b9ca2f7b690f545fa309e43b38068699db5)
for CMakeList.txt

The issue occurs during a downstream pass which does dialect conversion,
where both
[`FuncOpConversion`](https://github.com/llvm/llvm-project/blob/cde67b6663f994fcb4ded28fd79b23a13d347c4a/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp#L480)
and
[`SubviewFolder`](https://github.com/llvm/llvm-project/blob/cde67b6663f994fcb4ded28fd79b23a13d347c4a/mlir/lib/Dialect/MemRef/Transforms/ExpandStridedMetadata.cpp#L187)
are run together. The original starting IR is:
```mlir
module {
  func.func @foo(%arg0: memref<100x100xf32>, %arg1: index, %arg2: index, %arg3: index, %arg4: index) -> memref<?x?xf32, strided<[100, 1], offset: ?>> {
    %subview = memref.subview %arg0[%arg1, %arg2] [%arg3, %arg4] [1, 1] : memref<100x100xf32> to memref<?x?xf32, strided<[100, 1], offset: ?>>
    return %subview : memref<?x?xf32, strided<[100, 1], offset: ?>>
  }
}
```


After `FuncOpConversion` runs, the IR looks like:
```mlir
"builtin.module"() ({
  "llvm.func"() <{CConv = #llvm.cconv<ccc>, function_type = !llvm.func<struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)> (ptr, ptr, i64, i64, i64, i64, i64, i64, i64, i64, i64)>, linkage = #llvm.linkage<external>, sym_name = "foo", visibility_ = 0 : i64}> ({
  ^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr, %arg2: i64, %arg3: i64, %arg4: i64, %arg5: i64, %arg6: i64, %arg7: i64, %arg8: i64, %arg9: i64, %arg10: i64):
    %0 = "memref.subview"(<<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>) <{operandSegmentSizes = array<i32: 1, 2, 2, 0>, static_offsets = array<i64: -9223372036854775808, -9223372036854775808>, static_sizes = array<i64: -9223372036854775808, -9223372036854775808>, static_strides = array<i64: 1, 1>}> : (memref<100x100xf32>, index, index, index, index) -> memref<?x?xf32, strided<[100, 1], offset: ?>>
    "func.return"(%0) : (memref<?x?xf32, strided<[100, 1], offset: ?>>) -> ()
  }) : () -> ()
  "func.func"() <{function_type = (memref<100x100xf32>, index, index, index, index) -> memref<?x?xf32, strided<[100, 1], offset: ?>>, sym_name = "foo"}> ({
  }) : () -> ()
}) {llvm.data_layout = "", llvm.target_triple = ""} : () -> ()
```
The `<<UNKNOWN SSA VALUE>>`'s here are block arguments of a separate
unlinked block, which is disconnected from the rest of the IR (so not
only is the IR verifier-invalid, it can't even be parsed). This IR is
created by signature conversion in the dialect conversion infra.

Now `SubviewFolder` is applied, and the utility function here is called
on one of these disconnected block arguments, causing a crash.

The TestMemRefToLLVMWithTransforms pass is introduced to exercise the
bug, and it can be reused by other contributors in the future.

Co-authored-by: Rahul Kayaith <rkayaith@gmail.com>

---------

Signed-off-by: hanhanW <hanhan0912@gmail.com>

This reverts commit c3746ff3229c57110f7895ff5b93e520cead0d1b.

This breaks build with BUILD_SHARED_LIBS=ON.

```
/usr/bin/ld: CMakeFiles/MLIRTestMemRefToLLVMWithTransforms.dir/TestMemRefToLLVMWithTransforms.cpp.o: in function `(anonymous namespace)::TestMemRefToLLVMWithTransforms::runOnOperation()':
TestMemRefToLLVMWithTransforms.cpp:(.text._ZN12_GLOBAL__N_130TestMemRefToLLVMWithTransforms14runOnOperationEv+0x68): undefined reference to `mlir::LowerToLLVMOptions::LowerToLLVMOptions(mlir::MLIRContext*)'
/usr/bin/ld: TestMemRefToLLVMWithTransforms.cpp:[ 88%] Built target CodeGenTests
(.text._ZN12_GLOBAL__N_130TestMemRefToLLVMWithTransforms14runOnOperationEvmake[2]: Leaving directory '/work2/kparzysz/git/llvm.org/b/x86'
+0x80): undefined reference to `mlir::LLVMTypeConverter::LLVMTypeConverter(mlir::MLIRContext*, mlir::LowerToLLVMOptions const&, mlir::DataLayoutAnalysis const*)'
/usr/bin/ld: TestMemRefToLLVMWithTransforms.cpp:(.text._ZN12_GLOBAL__N_130TestMemRefToLLVMWithTransforms14runOnOperationEv+0x143): undefined reference to `mlir::populateFuncToLLVMConversionPatterns(mlir::LLVMTypeConverter const&, mlir::RewritePatternSet&, mlir::SymbolTable const*)'
/usr/bin/ld: TestMemRefToLLVMWithTransforms.cpp:(.text._ZN12_GLOBAL__N_130TestMemRefToLLVMWithTransforms14runOnOperationEv+0x174): undefined reference to `mlir::LLVMConversionTarget::LLVMConversionTarget(mlir::MLIRContext&)'
```

The issue occurs during a downstream pass which does dialect conversion,
where both
[`FuncOpConversion`](https://github.com/llvm/llvm-project/blob/cde67b6663f994fcb4ded28fd79b23a13d347c4a/mlir/lib/Conversion/FuncToLLVM/FuncToLLVM.cpp#L480)
and
[`SubviewFolder`](https://github.com/llvm/llvm-project/blob/cde67b6663f994fcb4ded28fd79b23a13d347c4a/mlir/lib/Dialect/MemRef/Transforms/ExpandStridedMetadata.cpp#L187)
are run together. The original starting IR is:
```mlir
module {
  func.func @foo(%arg0: memref<100x100xf32>, %arg1: index, %arg2: index, %arg3: index, %arg4: index) -> memref<?x?xf32, strided<[100, 1], offset: ?>> {
    %subview = memref.subview %arg0[%arg1, %arg2] [%arg3, %arg4] [1, 1] : memref<100x100xf32> to memref<?x?xf32, strided<[100, 1], offset: ?>>
    return %subview : memref<?x?xf32, strided<[100, 1], offset: ?>>
  }
}
```


After `FuncOpConversion` runs, the IR looks like:
```mlir
"builtin.module"() ({
  "llvm.func"() <{CConv = #llvm.cconv<ccc>, function_type = !llvm.func<struct<(ptr, ptr, i64, array<2 x i64>, array<2 x i64>)> (ptr, ptr, i64, i64, i64, i64, i64, i64, i64, i64, i64)>, linkage = #llvm.linkage<external>, sym_name = "foo", visibility_ = 0 : i64}> ({
  ^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr, %arg2: i64, %arg3: i64, %arg4: i64, %arg5: i64, %arg6: i64, %arg7: i64, %arg8: i64, %arg9: i64, %arg10: i64):
    %0 = "memref.subview"(<<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>, <<UNKNOWN SSA VALUE>>) <{operandSegmentSizes = array<i32: 1, 2, 2, 0>, static_offsets = array<i64: -9223372036854775808, -9223372036854775808>, static_sizes = array<i64: -9223372036854775808, -9223372036854775808>, static_strides = array<i64: 1, 1>}> : (memref<100x100xf32>, index, index, index, index) -> memref<?x?xf32, strided<[100, 1], offset: ?>>
    "func.return"(%0) : (memref<?x?xf32, strided<[100, 1], offset: ?>>) -> ()
  }) : () -> ()
  "func.func"() <{function_type = (memref<100x100xf32>, index, index, index, index) -> memref<?x?xf32, strided<[100, 1], offset: ?>>, sym_name = "foo"}> ({
  }) : () -> ()
}) {llvm.data_layout = "", llvm.target_triple = ""} : () -> ()
```
The `<<UNKNOWN SSA VALUE>>`'s here are block arguments of a separate
unlinked block, which is disconnected from the rest of the IR (so not
only is the IR verifier-invalid, it can't even be parsed). This IR is
created by signature conversion in the dialect conversion infra.

Now `SubviewFolder` is applied, and the utility function here is called
on one of these disconnected block arguments, causing a crash.

The TestMemRefToLLVMWithTransforms pass is introduced to exercise the
bug, and it can be reused by other contributors in the future.

---------

Signed-off-by: hanhanW <hanhan0912@gmail.com>

Co-authored-by: Rahul Kayaith <rkayaith@gmail.com>