Arguments are now treated as registers "written" at the beginning of
the first basic block. By modeling them this way, we can avoid all the
complicated logic on whether to use a local or the arguments array when
accessing any particular one of them. Furthermore, we can detect whether
they are overwritten or not. If they are not overwritten, we can
initialize them as a const reference into the arguments array. This way
we save a copy.
Treating the arguments as generic registers causes the basic blocks pass
to aggressively adjust their types, pushing some conversions back into
the QML engine. This is good. Unused arguments become void, for example,
and don't have to be passed at all. However, we also need a special case
for QJSPrimitiveValue arguments now.
Pick-to: 6.4
Fixes: QTBUG-104462
Change-Id: I994bea0929bd508aa41db58dee4a7f12cd20f053
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Sami Shalayel <sami.shalayel@qt.io>
In that case we need to allocate extra registers. We already did so
before, but we wouldn't use the registers afterwards.
This works nicely in 6.4 because we have a separate type for each store
operation. Therefore, the original function argument (being of a
different "type") won't be found in the list of local registers. Access
to it falls back on the actual arguments array. Only once we've stored
something into the register that mirrors the argument we can retrieve
it.
Pick-to: 6.4
Fixes: QTBUG-104462
Change-Id: Ibb0315cd2f8a8e4106d39fff88a6097b1623eb48
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Ulf Hermann