DPC++ daily 2022-01-12

[SYCL] Change matrix type (#5221)

Previously we relied on the structure type (which represented matrix
type) mangling to obtain its layout. Now, when DPCPP mangling scheme is
aligned with C++, thus the structure lost their usual mangling. Yet we
want to preserve the desired information within the matrix type, coming
from DPCPP headers. To achive this the 'Matrix structure' was changed
form:
template <typename T, int R, int C, int L, int S>
struct __spirv_JointMatrixINTEL;
to
template <typename T, int R, int C, int L, int S>
struct __spirv_JointMatrixINTEL {
T (*Value)[R][C][L + 1][S + 1];
};

so it's no longer an opaque structure and now it look like this in LLVM
IR:
%struct.__spirv_JointMatrixINTEL = type { [42 x [6 x [2 x [1 x i32]]]]* }

Here we encode the number of Rows, Cols, Layout and Scope as sizes of an
array (which element type is the same as the base matrix's type), which
is a bit odd, but it's probably the best way we can preserve the
information now without having the matrix type itself in LLVM.

Signed-off-by: Dmitry Sidorov <[email protected]>