b631590574
Adversarial review of B1.0b found a param-bearing abi(.pure) function
emitted invalid LLVM ("cannot use argument of naked function" — loud
verifier error, not silent) because the param-alloca loop spilled the
args to stack slots, which a naked function cannot have.
Fixed forward — this ENABLES the B1.3 context-switch use case rather
than rejecting it: gate the param-alloca loop on fd.abi != .pure in
decl.zig (both body-lowering paths) and generic.zig. A naked function's
args stay in their ABI registers and are read directly by the asm body
(e.g. swap_context reads from/to from x0/x1); the LLVM args are
declared-but-unused, which the verifier allows.
examples/1803-concurrency-pure-asm-param.sx: naked add(a, b) reads x0/x1
(add x0, x0, x1; ret) -> 40 + 2 = 42. aarch64-pinned.
Pack abi(.pure) (variadic + naked — nonsensical, can't read a runtime
pack from registers) left unsupported: pack.zig's param loop is
intertwined with comptime-param/#insert handling, so that case still
hits the loud verifier error. Documented in the checkpoint.
Also updates PLAN-FIBERS / CHECKPOINT-FIBERS for B1.0 completion.
B1.0 complete. Suite green (725/0).
26 lines
1.1 KiB
Plaintext
26 lines
1.1 KiB
Plaintext
// Stream B1 (fibers) — an `abi(.pure)` function with PARAMETERS reads its args
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// from ABI registers (the shape the fiber context-switch needs: `swap_context`
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// reads `from`/`to` from x0/x1).
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//
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// A naked function has no frame, so params are NOT spilled to stack slots — they
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// stay in their ABI registers and the asm body reads them directly. Here `a` is
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// in x0, `b` in x1 (aarch64 AAPCS), and the result returns in x0: `add x0, x0,
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// x1`. The lowering skips the param-alloca loop for `.pure` (decl.zig /
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// generic.zig); the LLVM args are declared-but-unused, which the verifier allows
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// (spilling them would emit `store i64 %0, …` → "cannot use argument of naked
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// function"). aarch64-pinned; runs end-to-end (exit 42), ir-only on a mismatch.
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//
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// Regression for an adversarial-review finding: before the param-alloca guard, a
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// param-bearing `.pure` fn emitted invalid LLVM (loud verifier error) instead of
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// a working naked function.
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add :: (a: i64, b: i64) -> i64 abi(.pure) {
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asm volatile {
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#string A
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add x0, x0, x1
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ret
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A
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};
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}
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main :: () -> i64 { return add(40, 2); }
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