!Inst

The !Inst tag declares an instruction that can be extended to form an instruction set. It is useful for declaring CPU instruction set extensions, or microcode instructions for a accelerator engine.

Warning

This tag is likely to be refactored into a more generic !Command description tag, that builds on the ideas of ‘extending’ a base tag to add more functionality. This would be more suited to other uses than the existing !Inst instruction description - with the current implementation only one field can be overridden or fixed to a value per instruction layer, this is likely to be replaced with a more flexible mechanism.

Usage

- Inst
  name  : root
  sd    : Base instruction from which everything extends
  fields:
  - !Field
    name : class
    lsb  : 0
    width: 5
    enums:
    - !Enum [load_store, 0]
    - !Enum [math,       1]
    - !Enum [logic,      2]

- !Inst
  name    : load_store
  base    : root
  decode_f: class
  decode_e: load_store
  fields  :
  - !Field
    name : operation
    lsb  : 5
    width: 2
    enums:
    - !Enum [load,  0]
    - !Enum [store, 1]
    - !Enum [clear, 2]
  - !Field
    name : operand_1
    lsb  : 7
    width: 5
  ...

- !Inst
  name    : load_to_reg
  base    : load_store
  decode_f: operation
  decode_e: load
  fields  :
  - !Field
    name : register
    lsb  : 12
    width: 5
  ...

class blade.schema.ph_inst.Inst(name, base='', decode_f='', decode_e='', options='', sd='', ld='', hir_ref='', hir_name='', fields=None, unrolled=None)

Declares an instruction that can be extended to create a similarly formed instruction set, where the value of an inherited field can be forced to a specific value.

__init__(name, base='', decode_f='', decode_e='', options='', sd='', ld='', hir_ref='', hir_name='', fields=None, unrolled=None)

Initialisation for the !Inst tag.

Parameters

• name – Name of the instruction

• base – Instruction to inherit from

• decode_f – Which field should be fixed to a certain value

• decode_e – What value from the enumeration of the field referenced by decode_f should be taken

• options – List of options in the form ‘KEY=VAL’ or just ‘KEY’ if a value is not required

• sd – Short description - maximum 150 characters

• ld – Long description - no limit on length

• hir_ref – Deprecated field - will be removed

• fields – List of !Field tags for the instruction

• unrolled – Deprecated field - will be removed

set_file_marks(start, end)

Set start and end marks of the declaration and propagate to children

Parameters

• start – The starting mark

• end – The ending mark

set_source_file(file)

Set the source file of this object and propagate it to children.

Parameters

file – The source file path or object

validate()

Check that this tag agrees with our YAML schema