nes-pascal

Record Implementation and Measurements (0.5.10)

Historical note: fixed-pool figures below record the 0.5.10 state. Milestone 0.5.11 now reserves zero expression bytes for this benchmark and recovers the complete 16-byte legacy window.

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Milestone 0.5.10 adds nominal, fixed-layout records as compiler metadata and contiguous static storage. RecordType retains the name, ordered typed fields, zero-based offsets, total size, and nominal identity. Parsed and resolved field reads/writes remain explicit through semantic analysis, temporary analysis, memory layout, benchmark reporting, and ca65 generation.

Layout and lowering

• byte, boolean, and enum fields each occupy one byte with no padding.
• Standalone records and arrays of records are allocated contiguously in regular RAM and are excluded from automatic Zero Page promotion.
• A standalone or constant-index field becomes a direct symbol-plus-offset operand. A 4-byte record at index 2 uses base + 8 before its field offset.
• Variable record-array indexes are multiplied by the compile-time record size: powers of two use asl; other sizes use local repeated addition. No generic multiplication runtime or permanent temporary is linked.
• Indexed writes evaluate the index first and preserve the scaled offset on the hardware stack across right-hand-side evaluation.
• Variable access is rejected when a selected field’s maximum scaled offset can exceed 255. Constant indexes remain direct ca65 address expressions.

Representative lowering is:

    lda #$20
    sta variable_Player

    lda variable_Index
    asl a
    asl a
    clc
    adc #$01
    tax
    lda variable_Enemies,x

Records benchmark

The records workload uses a 4-byte entity, a four-element entity array, standalone record fields, enum and Boolean fields, constant/variable indexes, field reads and writes, arithmetic, and an enum-field branch.

Metric	Result
PRG code	389 B
PRG occupied	395 B
Instructions	196
Estimated static base cycles	605
Expression tree depth	2
Maximum live expression temporaries	0
Fixed temporary pool reservation	16 B
Temporaries/cache actually required	0 B
Record storage	20 B regular RAM
Other regular user storage	1 B
Automatically promoted scalar storage	2 B ZP
ZP benchmark allocated/reserved	27 B
ZP allocator-visible free	126 B
Regular allocator-visible free	1,511 B
Runtime features	None

The record array contributes 16 bytes and the standalone record 4 bytes. The index and result scalars follow the existing promotion policy; no record, field, descriptor, scaling cache, or runtime helper consumes Zero Page.

All 19 pre-existing benchmark workloads retain their previous PRG, instruction, cycle, RAM, Zero Page, and temporary-pressure metrics. Programs without records emit no record-specific storage, code, metadata, or runtime feature.

Final local validation passed 486 automated tests and the dedicated 27-test Mesen runtime suite. The public records example assembled and linked as a valid NROM image, and the complete benchmark corpus reconciled its 2 KiB RAM totals.

Deliberately deferred

Nested and anonymous records, whole-record assignment/equality, record parameters and returns, references, pointers, packed/variant records, methods, constructors, destructors, RTTI, runtime bounds checks, multidimensional arrays, a multiplication runtime, and temporary allocator redesign remain outside this milestone.

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