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AArch64: Add support for more extending loads #9657

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2245ba0
AArch64: Add support for more extending loads
david-arm Nov 4, 2025
57f1713
Address review comments
david-arm Dec 15, 2025
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38 changes: 22 additions & 16 deletions hphp/runtime/vm/jit/vasm-simplify-arm.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -91,26 +91,32 @@ bool simplify(Env& env, const cmovq& inst, Vlabel b, size_t i) {

///////////////////////////////////////////////////////////////////////////////

bool simplify(Env& env, const loadb& inst, Vlabel b, size_t i) {
if (if_inst<Vinstr::movzbl>(env, b, i + 1, [&] (const movzbl& mov) {
// loadb{s, tmp}; movzbl{tmp, d}; -> loadzbl{s, d};
if (!(env.use_counts[inst.d] == 1 && inst.d == mov.s)) return false;
template <Vinstr::Opcode ExtOp, typename ExtMov, typename ExtLoad, typename Load>
bool simplify_load_ext(Env& env, const Load& inst, Vlabel b, size_t i) {
return if_inst<ExtOp>(env, b, i + 1, [&] (const ExtMov& mov) {
if (env.use_counts[inst.d] != 1 || inst.d != mov.s) return false;

return simplify_impl(env, b, i, [&] (Vout& v) {
v << loadzbl{inst.s, mov.d};
v << ExtLoad{inst.s, mov.d};
return 2;
}); })) {
return true;
}

return if_inst<Vinstr::movsbl>(env, b, i + 1, [&] (const movsbl& mov) {
// loadb{s, tmp}; movsbl{tmp, d}; -> loadsbl{s, d};
if (!(env.use_counts[inst.d] == 1 && inst.d == mov.s)) return false;
});
});
}

return simplify_impl(env, b, i, [&] (Vout& v) {
v << loadsbl{inst.s, mov.d};
return 2;
}); });
bool simplify(Env& env, const loadb& inst, Vlabel b, size_t i) {
if (simplify_load_ext<Vinstr::movzbl, movzbl, loadzbl>(env, inst, b, i)) {
return true;
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@charles-typ charles-typ Dec 12, 2025 •
edited
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I'm help dumping the reviewer comments from @ottoni because it's not passing through our review system.

HHVM's coding style require the { and } even on single-statement blocks (unless the return is in the same line as the if).
Same for the other ifs below.

}
if (simplify_load_ext<Vinstr::movzbq, movzbq, loadzbq>(env, inst, b, i)) {
return true;
}
if (simplify_load_ext<Vinstr::movsbl, movsbl, loadsbl>(env, inst, b, i)) {
return true;
}
if (simplify_load_ext<Vinstr::movsbq, movsbq, loadsbq>(env, inst, b, i)) {
return true;
}
return false;
}

///////////////////////////////////////////////////////////////////////////////
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