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Heterogeneous container format (HCF) documentation

In all compilation flows in which Open SYCL takes responsibility for embedding device code in the host binary, the embedded device code will be in the HCF format.

HCF is a format that has been designed to be easy to parse, and allow binary content as well as text-based metadata to coexist in a flexible hierarchical structure.

The Open SYCL runtime can be instructed to dump the HCF data embedded in the application by setting the environment variable HIPSYCL_HCF_DUMP_DIRECTORY (details).

opensycl-hcf-tool can be used to inspect or alter HCF files.

HCF definition

<HCF> ::= <ReadableHeader>'__hipsycl_hcf_binary_appendix'<BinaryAppendix>
<ReadableHeader> ::= <NodeContentLines>
<NodeContentLines> ::= <KeyValueLine> | <Subnode> | <KeyValueLine><NodeContentLines> | <Subnode><NodeContentLines> | ø
<KeyValueLine> ::= [<Whitespaces>]<Key>[<Whitespaces>] '=' [<Whitespaces>]<Value>[<Whitespaces>]'\n'
<Subnode> ::= [<Whitespaces>] '{.'<UniqueSubnodeName> [<Whitespaces>] '\n' 
    <NodeContentLines> 
    [<Whitespaces>] '}.' <UniqueSubnodeName> [<Whitespaces>]  '\n'

UniqueSubnodeName is a string that is unique among all subnodes of the parent node.

<BinaryAppendix> is a binary blob that contains the concatenated binary data from all nodes. Binary data is attached to nodes by adding a subnode:

{.__binary
  start=<StartOffsetInBinaryAppendix>
  size=<SizeInBytes>
}.__binary

Example

The following HCF data contains a root node, two subnodes, and one binary appendix containing 'ABC':

a = 123
b = asd64
{.MySubnode
  keyname = Hello
  {.__binary
    start = 0
    size = 3
  }.__binary
  key2 = World
}.MySubnode
{.MySubnode2
  keyname = Turtle
}.MySubnode2
__hipsycl_hcf_binary_appendixABC