Sizes and Offsets
The intermediate language aims to be platform independent. In particular, it supports both 32- and
64-bit systems. Since the size of a pointer differs on 32- and 64-bit systems, the sizes of data
structures typically differ between the two. For this reason, the intermediate language provides two
datatypes, core.asm.Size and core.asm.Offset to make it easier to work with
sizes and offsets in a platform-agnostic manner. Both types achieve this by storing both a 32-bit
and a 64-bit size and offset respectively.
Size
The core.asm.Size type represents the size of some data in memory. As mentioned above, the Size
type contains two versions of the size. One for 32-bit systems, and another for 64-bit systems.
Each size consists of an unsigned integer that represents the size. In addition, each size contains
the alignment of the data. The size portion of the data is not aligned internally, but it is
automatically aligned when it is retrieved. The 32-bit size is retrieved through the member
size32, and the 64-bit size is retrieved through the member size64. In portable code, the member
current can be used to retrieve the size for the current platform.
Since the size is not aligned internally, addition and multiplication operates on the unaligned
size. It is, however, possible to force alignment of the internal size by calling the aligned
member. Similarly, it is possible to remove the internal alignment by calling the unaligned
member.
There are a number of pre-defined constants in the package core.asm that create sizes
for Storm types:
-
core.asm.Size core.asm.sPtr()- create a size for a pointer (4/8 bytes) -
core.asm.Size core.asm.sByte()- create a size for aByte(1 byte) -
core.asm.Size core.asm.sInt()- create a size for aInt(4 bytes) -
core.asm.Size core.asm.sNat()- create a size for aNat(4 bytes) -
core.asm.Size core.asm.sLong()- create a size for aLong(8 bytes) -
core.asm.Size core.asm.sWord()- create a size for aWord(8 bytes) -
core.asm.Size core.asm.sFloat()- create a size for aFloat(4 bytes) -
core.asm.Size core.asm.sDouble()- create a size for aDouble(8 bytes)
Offset
The core.asm.Offset type represents an offset into a type. An offset is signed and can
thereby be negative. Furthermore, the offset does not carry an alignment. It can, however, be
manually aligned using the alignAs member. The stored value can be retrieved using v32 or v64
for specific offsets, or using the current member for the current platform.