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fix(lua/jit): expose CALL_INT's second arg to hir_val_operand

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CALL_INT packs arg1's instruction index into val[]; without teaching
liveness about that, the second argument can look dead and be recycled
before the ECALL — the same class of silent failure as #1711's field keys.
This commit is contained in:
Stephen Dennis 2026-07-28 19:57:51 +00:00
parent d76bdf90fb
commit 20d39472fa
1 changed files with 20 additions and 13 deletions
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33
mux/include/hir.h
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@ -712,25 +712,32 @@ struct hir_program {
// Almost every instruction keeps its operands in src1/src2, with the
// CALL/STRCAT and PHI side arrays as the two documented exceptions that
// operand walkers already special-case. HIR_LUA_SETI is a third
// exception and a much easier one to miss: seti(tbl,key,value) and
// setfield(tbl,key,value) both park the VALUE here
// and the VALUE is an instruction index parked in val[] (see the
// HIR_LUA_SETI case in hir_codegen.cpp, which reads it back as `s3`).
// exception and a much easier one to miss: seti/setfield park the VALUE
// here; CALL_INT packs nargs in the low 8 bits and the *second* arg's
// instruction index above that (src2 holds the first arg). A walker that
// misses either treats the operand as dead -- DCE / regalloc reuse -- while
// the ECALL still expects it (#1711 was that shape for field keys).
//
// A walker that misses it will treat the stored value as dead, so DCE
// can NOP it and the register allocator can reuse its register while
// the SETI still expects it. val[] is a plain integer for every other
// opcode -- for HIR_LUA_ALOAD it is a guest ADDRESS -- so this must
// stay strictly gated on the opcode.
// val[] is a plain integer for every other opcode -- for HIR_LUA_ALOAD it
// is a guest ADDRESS -- so this must stay strictly gated on the opcode.
//
// Returns the operand's instruction index, or -1 when there is none.
// CALL_INT exposes only arg1 this way; a true N-ary operand list is the
// longer-term fix the #1519 call path argues for.
//
inline int hir_val_operand(const hir_program &h, int i) {
if (i < 0 || i >= h.n_insns) return -1;
if (h.kind[i] != HIR_LUA_SETI && h.kind[i] != HIR_LUA_SETFIELD) {
return -1;
if (h.kind[i] == HIR_LUA_SETI || h.kind[i] == HIR_LUA_SETFIELD) {
int v = static_cast<int>(h.val[i]);
return (v >= 0 && v < h.n_insns) ? v : -1;
}
int v = static_cast<int>(h.val[i]);
return (v >= 0 && v < h.n_insns) ? v : -1;
if (h.kind[i] == HIR_LUA_CALL_INT) {
// low 8 = nargs; high bits = a1_insn + 1 (0 means "no second arg").
//
int a1i = static_cast<int>(h.val[i] >> 8) - 1;
return (a1i >= 0 && a1i < h.n_insns) ? a1i : -1;
}
return -1;
}
// SSA construction (hir_ssa.cpp).