Add a count-only mode to the Writer (advance pos without storing) and factor the
section walk into emit_module, so encode and the new encoded_size(m) share one
path. encoded_size returns the exact byte count encode will produce -- the SPIR-V
analog of an ISA's encode_max_code_size, here exact rather than an upper bound.
The printer now sizes its scratch buffer with it instead of retry-on-overflow.
Verified: encoded_size == encode byte_count; suite 10 passed.
Type-defining instructions the codec doesn't model structurally -- OpTypeImage,
OpTypeSampler, OpTypeSampledImage, OpTypeMatrix, OpTypeOpaque, OpTypeEvent,
OpTypeDeviceEvent, OpTypeReserveId, OpTypeQueue, OpTypePipe -- decode to
Type{.OPAQUE} plus an Opaque_Info{opcode, words} side entry (the operand words
after the result <id>) and re-emit verbatim. One generic fallback covers every
opaque SPIR-V type byte-exact, with no per-type fields.
Test: image_type (OpTypeImage, 7 operands) round-trips -> 9 passed.
- Definition order: Module.defs records the exact type/constant/global
interleaving (SPIR-V's single 'types, constants, global variables' section must
be dependency-ordered -- a length constant before the array type that uses it,
etc.). decode records it; encode replays it for byte-exact, spec-valid output
(empty defs falls back to all-types, then -constants, then -globals).
emit_one_type/constant/global factored out for the replay; no encoder alloc.
- OpTypeRuntimeArray: ARRAY with len_ref == ID_NONE (vs OpTypeArray's <id> length).
Tests: bool_and_array sets defs so OpConstant precedes OpTypeArray (verified in
disasm); runtime_array added -> 7 passed.
Extend the shared type model so SPIR-V's OpTypeBool and OpTypeArray (whose length
is a constant <id>, not a literal) lower cleanly:
- ir.Type_Kind gains BOOL (a distinct boolean; LLVM i1 will use it too).
- ir.Type gains len_ref: Id -- an ARRAY length carried as a constant <id>
(alongside the existing literal count for dialects with literal lengths).
- type_bool / type_array constructors.
SPIR-V codec: OpTypeBool <-> Type{.BOOL}; OpTypeArray <-> Type{.ARRAY, elem,
len_ref}. Test bool_and_array round-trips byte-exact -> 6 passed.
NOTE: a spec-valid module orders an array's length constant before the array
type; the codec round-trips the shape byte-exact regardless, but emitting the
types/constants section in dependency order is a follow-up.
- OpFunctionParameter: the entry block's Block.params round-trip as
OpFunctionParameter (emitted between OpFunction and the entry OpLabel, decoded
back onto the entry block).
- encode computes bound (max <id> + 1) when the caller leaves it 0; a non-zero
bound (e.g. from decode) is preserved, so re-encode is stable.
- Trailing operands an enum value/bit pulls in (MemoryAccess Aligned's alignment,
...) are captured on decode as literals, so enum-parameter instructions
re-encode byte-exact.
Tests: param_function + load_aligned added -> 5 passed.
The second half of encode(): the <id> side tables (Module.type_ids /
global_ids / function_ids -- SPIR-V's flat id space, which ir.Type/Global/
Function don't carry) plus the lowering:
emit_types ir.Type -> OpTypeXxx (void/int/float/vector/pointer/struct/
function; INT signedness + POINTER storage class ride in aux)
emit_constants OpConstant / OpConstantComposite / true/false/null
emit_globals OpVariable (storage class from the pointer type)
emit_operation generic table-driven op emit: INSTRUCTION_INDEX gives the
result-type/result-id prefix, the rest stream from op.operands
emit_functions OpFunction / OpLabel / body / OpFunctionEnd
Validated: a complete void compute main module encodes to byte-exact-correct
SPIR-V (29 words, all checked). Known gaps: OpFunctionParameter, ARRAY/bool
types, explicit enum-parameter operands, computed bound. Decoder next.
The Module -> word-stream encoder's first half: a fast single-pass word writer
(one host-endian store per word; instruction headers written as a placeholder
and backpatched, so variable-length instructions need no measure pass) plus the
header and the preamble / debug / annotation sections in spec layout order
(capabilities, extensions, ext-inst imports, memory model, entry points,
execution modes, OpString/OpSource/OpName, decorations).
Validated: a minimal module encodes to byte-exact-correct SPIR-V (magic, v1.5,
OpCapability Shader, OpMemoryModel Logical GLSL450, OpEntryPoint GLCompute %main,
NUL-terminated 'main' string, correct backpatched word counts).
Types/constants/globals/function bodies (the <id> + type lowering) are next.
