066ba54346
A `%[name]` that references a symbol ("s") operand without an explicit
modifier now lowers to `${N:c}` (LLVM 'bare constant — no punctuation')
instead of `${N}`. This makes `bl %[fn]` / `call %[fn]` portable across
targets with no per-arch knowledge: x86 would otherwise render `$cb`
(an invalid call target, requiring a hand-written `:P`); aarch64 is
unaffected. Verified `:c` is equivalent to `:P` for x86-64 calls (both
emit R_X86_64_PLT32), and correct for branch targets, RIP-relative
addressing, and `$`-prefixed absolute immediates.
renderAsmTemplate injects `:c` only for symbol operands lacking an
explicit modifier (asmNamedIsSymbol helper); an explicit `%[name:X]`
still wins (escape hatch). x86 example 1659 drops its `:P` for the same
plain `%[fn]` as aarch64 1656. Snapshots regen to `${N:c}`. zig build
test green (668 corpus, 446 unit).
20 lines
994 B
Plaintext
20 lines
994 B
Plaintext
// ASM stream — symbol operand (`"s"`) on x86_64 (cross-arch sibling of the
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// aarch64 1656). A DIRECT `call` to an `export`ed sx function by symbol, written
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// with the SAME portable `%[fn]` as the aarch64 example — the compiler injects
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// the `:c` operand modifier for symbol operands, so the symbol prints bare on
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// every target (x86 would otherwise render `$cb`, a bad call target). The
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// backend emits the platform-mangled name (`call cb` on Linux). x86-pinned;
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// ir-only here, runs on x86_64-linux. Round trip: sx → asm → call cb → 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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"call %[fn]",
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[ret] "={rax}" -> i64,
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"{rdi}" = n, // arg in rdi (SysV)
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[fn] "s" = cb, // symbol operand → direct `call cb`
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clobbers(.rcx, .rdx, .rsi, .r8, .r9, .r10, .r11, .memory),
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};
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}
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main :: () -> i64 { if tramp(41) != 42 { return 1; } return 0; }
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