c187122531
A symbol operand (constraint "s") feeds a function/global symbol whose mangled name the template emits — enabling a DIRECT `bl %[fn]` (one fewer indirection than register-indirect `blr`). Until now `"s" = fn` fell through to emit and produced an LLVM-verifier crash (param type mismatch). Reject it at lowering with a clear diagnostic instead, and lock that with examples/1656-platform-asm-symbol-operand.sx. The next commit implements it and flips the example to run (→ 42).
25 lines
955 B
Plaintext
25 lines
955 B
Plaintext
// ASM stream — symbol operand (`"s"`): feed a function/global SYMBOL into the
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// template so a DIRECT `bl %[fn]` (PC-relative, one fewer indirection than a
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// register-indirect `blr`) branches straight to it, with the platform-mangled
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// name emitted by the backend (so the template stays portable — no hardcoded
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// `_` underscore). Not yet implemented — rejected at lowering for now. The next
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// commit implements it and flips this example to run (sx → asm → sx, → 42).
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cb :: (n: i64) -> i64 export "cb" { return n + 1; }
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tramp :: (n: i64) -> i64 {
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return asm volatile {
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#string ASM
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stp x29, x30, [sp, #-16]!
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mov x0, %[arg]
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bl %[fn]
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mov %[res], x0
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ldp x29, x30, [sp], #16
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ASM,
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[res] "=r" -> i64,
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[arg] "r" = n,
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[fn] "s" = cb, // symbol operand → direct `bl _cb`
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clobbers(.x0, .x30, .memory),
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};
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}
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main :: () -> i64 { return tramp(41); }
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