Air::spillEverything and Air::iteratedRegisterCoalescing don't take into account Inst::extraClobberedRegs()

• Component: JavaScriptCore
• Status: RESOLVED DUPLICATE

[Filip Pizlo]

Both allocators have a loop devoted to ensuring that all Def's interfere with each other.  Inst::extraClobberedRegs() is like an extra set of Def's.

This is important because it's what ensures that we don't put something into a register that is clobbered by a call.

[Filip Pizlo]

I think that both allocators want an abstraction like:

inst.forEachTmpIncludingExtra(
    [&] (Tmp tmp, Arg::Role role, Arg::Type type) {
        // tmp is not a reference, since we cannot edit an extraClobberedReg.
    });

This could be implemented as:

template<typename Functor>
void forEachTmpIncludingExtra(const Functor& functor)
{
    forEachTmp(
        [&] (Tmp& tmp, Arg::Role role, Arg::Type type) {
             functor(tmp, role, type);
        });
    if (hasSpecial()) {
        extraClobberedRegs().forEach(
            [&] (Reg reg) {
                functor(Tmp(reg), Arg::Def, reg.isGPR() ? Arg::GP : Arg::FP);
            });
    }
}

Armed with such an abstraction, we could fix the bug by just changing which method the register allocators call when handling Def-to-Def interference.

[Benjamin Poulain]

Fixed in https://bugs.webkit.org/show_bug.cgi?id=151246

*** This bug has been marked as a duplicate of bug 151246 ***