cdd920b692
Adds examples/1651-platform-asm-x86-syscall-write.sx — the canonical
inline-asm use case: `write(2)` via a raw x86_64 `syscall` (SYS_write
in rax, fd/buf/count pinned to rdi/rsi/rdx, rcx+r11+memory clobbered,
byte count returned in rax). Exercises register-pinned inputs, a pinned
value output, a pointer input (*u8 -> rsi), and clobbers(.…) lowering
together.
x86-pinned via .build { "target": "x86_64-linux" }: ir-only on this
aarch64 host (the .ir snapshot locks the exact constraint string
`={rax},{rax},{rdi},{rsi},{rdx},~{rcx},~{r11},~{memory}` — the §II.11
silent-miscompile risk zone), runs natively on x86_64-linux printing
"ok\n" (hand-authored .stdout, asserted only in execute mode).
Pure additive test coverage — no compiler change (lock commit).
zig build test green (660 corpus, 446 unit).
28 lines
1.3 KiB
Plaintext
28 lines
1.3 KiB
Plaintext
// ASM stream — x86_64 Linux `write(2)` via a raw `syscall`. The canonical inline-
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// asm use case: SYS_write (rax=1) with fd/buf/count pinned to rdi/rsi/rdx, the
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// `syscall` instruction clobbering rcx + r11 (+ memory), and the byte count
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// returned in rax. Demonstrates register-pinned inputs, a pinned value output,
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// a pointer input (`*u8` → rsi), and `clobbers(.…)` lowering all at once.
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//
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// x86-pinned via `.build`: ir-only on a non-x86 host — the `.ir` snapshot locks
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// the exact constraint string (`={rax},{rax},{rdi},{rsi},{rdx},~{rcx},~{r11},
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// ~{memory}`), which is the §II.11 silent-miscompile risk zone — and runs
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// natively on x86_64-linux (printing "ok\n"). See 1640 for an x86 multi-output
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// example, 1645/1647/1649/1650 for aarch64 examples that execute on this host.
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sys_write :: (fd: i64, buf: *u8, count: i64) -> i64 {
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return asm volatile {
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"syscall",
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[ret] "={rax}" -> i64, // return: bytes written, in rax
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"{rax}" = 1, // SYS_write (x86_64 Linux)
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"{rdi}" = fd, // fd
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"{rsi}" = buf, // buf
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"{rdx}" = count, // count
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clobbers(.rcx, .r11, .memory),
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};
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}
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main :: () {
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msg : [3]u8 = .[111, 107, 10]; // "ok\n"
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n := sys_write(1, @msg[0], 3);
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}
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