1040b8c776
Restructures the .asm_expr lowering arm into lowerAsmExpr, which validates the
asm shape with specific named diagnostics BEFORE the not-yet-implemented codegen
bail, so the user sees the real problem first. Two checklist items enforced:
- template must be a compile-time-known string ("..." or #string), not a
runtime expression;
- an asm with no value outputs must be `volatile` (else its effects could be
deleted) — mirrors Zig's rule.
Valid shapes still bail with the "codegen not yet implemented" message. Result-
type derivation + the operand auto-naming rule stay deferred to Phase C, where a
real IR op makes the result type observable/testable.
Locked with 1641-platform-asm-missing-volatile (the volatile error) and
1642-platform-asm-nop-volatile (no-output + volatile accepted → codegen bail).
zig build test green (650 corpus, 445 unit).
128 lines
8.1 KiB
Markdown
128 lines
8.1 KiB
Markdown
# sx Inline Assembly — Checkpoint (ASM stream)
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Companion to `current/PLAN-ASM.md`; design in
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[docs/inline-asm-design.md](../docs/inline-asm-design.md). Update after every
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commit, one step at a time per the cadence rule (no commit may both add a test
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and make it pass).
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## Last completed step
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**B.0** — asm shape validation (compile-path diagnostics). Restructured the
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`.asm_expr` lowering arm into `lowerAsmExpr` (`src/ir/lower/expr.zig`, mixed into
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`Lowering` in `src/ir/lower.zig`): it validates BEFORE the not-yet-implemented
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codegen bail, so the user sees the real problem first. Two checklist items now
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enforced with named diagnostics: (1) **template must be a compile-time-known
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string** (`"..."` / `#string`); (2) **no value outputs ⇒ must be `volatile`**
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(mirrors Zig — a result-less asm could be deleted). Valid shapes still bail with
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the "codegen not yet implemented" message. Result-type derivation + auto-naming
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stay deferred to a later step (observable only once Phase C produces a real IR
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op). Locked with `examples/1641-platform-asm-missing-volatile.sx` (volatile
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error) + `1642-platform-asm-nop-volatile.sx` (volatile no-output accepted →
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codegen bail). `zig build test` green (650 corpus, 0 failed; 445 unit). Files:
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`src/ir/lower/expr.zig`, `src/ir/lower.zig`, `examples/164{1,2}-*`.
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Prior: **A.1** — parse `asm { … }` + loud lowering bail (folded A.1+A.2 into one honest
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lock commit, since the loud bail IS current correct behavior — cadence option
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(a)). Added `AsmExpr`/`AsmOperand` to `src/ast.zig` + the `asm_expr` `Node.Data`
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arm; `parseAsmExpr` in `src/parser.zig` (`parsePrimary` `.kw_asm` dispatch) —
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parses the template, flat operand list (`[name]? "constraint" -> Type` value
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output / `= expr` input), and `clobbers(.…)`; `volatile`/`clobbers` recognized
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contextually via `isContextualWord`. The new `asm_expr` tag forced (and got)
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arms in three exhaustive `Node.Data` switches: `src/sema.zig` `analyzeNode` +
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`findNodeAtOffset`, `src/ir/semantic_diagnostics.zig` `checkBindingNames` (all
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recurse into template + operand payloads). Lowering bails LOUD + named in
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`src/ir/lower/expr.zig` ("inline assembly codegen is not yet implemented…") via
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an explicit `.asm_expr` arm (not the generic `unknown_expr` else) returning
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`emitPlaceholder`. `-> @place` write-through is rejected with a clear "Phase 2"
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parse error. Locked with `examples/1640-platform-asm-parse.sx` (multi-output
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`divmod`, named operands, register pins, clobbers — parses then bails; called
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from `main`). `zig build test` green (648 corpus, 0 failed; 445 unit). Files:
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`src/ast.zig`, `src/parser.zig`, `src/sema.zig`, `src/ir/semantic_diagnostics.zig`,
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`src/ir/lower/expr.zig`, `examples/1640-*`.
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Prior: **A.0** — `kw_asm` keyword (first compiler code). Added the `kw_asm` `Token.Tag`
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variant + `.{ "asm", .kw_asm }` keyword-map entry in `src/token.zig`; `volatile` /
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`clobbers` deliberately stay OUT of the global table (contextual). New exhaustive
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`Tag` switch in `src/lsp/server.zig` `classifyToken` flagged the missing arm (the
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intended coverage tripwire) — added `.kw_asm` to the keyword group. Lock test in
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new `src/lexer.test.zig` (`asm`→`kw_asm`, `volatile`/`clobbers`→`identifier`),
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wired into the `src/root.zig` barrel as `lexer_tests`. `zig build test` green (648
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corpus, 0 failed; 445 unit, 0 failed — +1). Files: `src/token.zig`,
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`src/lexer.test.zig`, `src/root.zig`, `src/lsp/server.zig`.
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Prior: **0.2** — CLAUDE.md docs for `<name>.build`; **Phase 0 COMPLETE**.
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**0.1** — corpus runner **ir-only branch** for cross-target examples. Replaced
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0.0's loud placeholder bail: when `cfg.target` doesn't match the host (`ir_only`),
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`sweepRoot` skips run/build/exec and verifies via `sx ir --target` only —
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asserting `.exit` (ir cmd) + `.ir` (normalized stdout) + `.stderr`, never
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`.stdout` (write skipped in update mode, assertion skipped in verify mode). An
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`.ir` snapshot is **required** in ir-only mode — its absence is a loud failure
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("needs an .ir snapshot for ir-only mode"). Locked with
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`examples/1639-platform-target-cross.sx` (asm-free `main :: () -> i64 { return 0;
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}`), `.build` `{ "target": "x86_64-linux" }`, + checked-in `.ir`. Verified both
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guards fire: corrupting the `.ir` → IR mismatch; deleting it → the require-failure.
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`zig build test` green (647 corpus, 0 failed; 444 unit). Files:
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`src/corpus_run.test.zig`, `examples/1639-*`.
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## Current state
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Phase A underway: `asm { … }` lexes (A.0) and **parses** into `AsmExpr` (A.1);
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lowering bails LOUD + named (no IR op / emit yet). Result-type derivation, the
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operand auto-naming rule, and the validation checklist are **Phase B** (not yet
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implemented — any asm reaching lowering errors out). The adopted **operand
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auto-naming rule** (design §II.5, decided this session): name auto-derived from a
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`{reg}` pin; explicit `[name]` only when it differs or for register-class (`=r`)
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operands; echo form `[eax] "={eax}"` rejected. Parser stores `name: ?[]const u8`;
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the rule is a Phase-B (typing) concern, so the parser needs no change for it.
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Known orthogonal bug: **issue 0137** — `sx run` on a program with no `main`
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segfaults (`src/target.zig:256-273`, unguarded JIT entry lookup). Pre-existing,
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asm-independent; does NOT block the ASM stream (every example has a `main`).
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Phase B–E feasibility already confirmed against the live tree
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(`LLVMGetInlineAsm` / `LLVMBuildCall2` / `LLVMAppendModuleInlineAsm` in LLVM@19
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`Core.h`; ERR-stream `extractvalue`→tuple in `emit_llvm.zig:726-927`; lib-less
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`extern`, 60 sites; `--target` a global CLI flag).
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## Next step
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**B.1 / C.0** — two viable directions:
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- **B.1 (more validation, testable now):** remaining checklist items that fire
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pre-codegen — echo-name rejection (`[eax] "={eax}"`, §II.5 auto-naming),
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duplicate operand names, `%[name]` references that name no operand. Add to
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`lowerAsmExpr` (same compile-path pattern). Each is a pinnable error example.
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- **C.0 (IR op, unlocks the rest):** add `inline_asm: InlineAsm` to `Op`
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(`src/ir/inst.zig`) + interp `bailDetail`; then `lowerAsmExpr` stops bailing
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and builds the op, at which point **result-type derivation becomes observable**
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(so the auto-naming rule + tuple result typing in `expr_typer.zig` can be
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tested end-to-end). See `PLAN-ASM.md` Phase C + design §II.6.
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Recommended: finish the cheap B.1 validation diagnostics, then move to C.0.
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(Result-type derivation in `expr_typer.zig` is intentionally deferred until C
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makes it observable — see Current state.)
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## Log
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- (init) Plan + design doc written; ASM stream opened.
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- (0.0) Corpus runner target-gating: `<name>.build` JSON config (replaces `.aot`
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marker), `--target` threading, `hostMatchesTarget` execute-gate, loud
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cross-target placeholder bail. Migrated 1226/1227 `.aot`→`.build`; locked with
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1638 fixture + unit tests. `zig build test` green.
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- (0.1) ir-only branch: cross-target examples verify via `sx ir --target` only
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(exit+ir+stderr, no stdout; `.ir` required). Locked with 1639 fixture; verified
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corrupt-.ir → mismatch and missing-.ir → loud failure. `zig build test` green.
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- (0.2) docs: CLAUDE.md documents `<name>.build` JSON sidecar (aot + target +
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ir-only gating), replacing stale `.aot` marker prose. **Phase 0 COMPLETE.**
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- (A.0) `kw_asm` keyword in token.zig (+ map entry); LSP `classifyToken` switch
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coverage; lock test in new `lexer.test.zig` (wired via root.zig). `volatile` /
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`clobbers` stay contextual identifiers. `zig build test` green (445 unit, +1).
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- (A.1) parse `asm { … }` → `AsmExpr` + loud lowering bail; `asm_expr` arms in 3
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exhaustive `Node.Data` switches; `-> @place` rejected (Phase 2). Adopted operand
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auto-naming rule (design §II.5). Locked with 1640 fixture. Filed orthogonal
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issue 0137 (no-`main` JIT segfault). `zig build test` green (648 corpus, 445 unit).
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- (B.0) asm shape validation in `lowerAsmExpr`: comptime-string template +
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no-output⇒volatile, with named diagnostics before the codegen bail. Locked with
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1641 (volatile error) + 1642 (volatile accepted). `zig build test` green (650
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corpus, 445 unit).
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## Known issues
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- **0137** — `sx run` on a program with no `main` segfaults (unguarded JIT entry
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lookup, `src/target.zig:256-273`). Pre-existing, asm-independent. Filed
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`issues/0137-jit-run-no-main-segfault.md`. Does not block A.1.
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