regmove, regfill, and regspill have immediates which aren't value
operands, so they aren't in the set of things that can be described by
the existing constraint system. Consequently, constraints saying that
the non-REX encodings only support registers that don't need REX
prefixes don't work. Fow now, just remove the non-REX encodings, so
that they don't get selected when they aren't valid.
This fixes the last known issue with instruction shrinking, so it can
be re-enabled.
Add a calling-convention setting to the `Flags` used as part of the
`TargetIsa`. This allows Cretonne code that generates calls to use the
correct convention, such as when emitting libcalls during legalization
or when the wasm frontend is decoding functions. This setting can be
overridden per-function.
This also adds "fast", "cold", and "fastcall" conventions, with "fast"
as the new default. Note that "fast" and "cold" are not intended to be
ABI-compatible across Cretonne versions.
This will also ensure Windows users will get an `unimplemented!` rather
than silent calling-convention mismatches, which reflects the fact that
Windows calling conventions are not yet implemented.
This also renames SpiderWASM, which isn't camel-case, to Baldrdash,
which is, and which is also a more relevant name.
When an instruction has multiple valid encodings, such as with and
without a REX prefix on x86-64, Cretonne typically picks the encoding
which gives the register allocator the most flexibility, which is
typically the longest encoding. This patch adds a pass that runs after
register allocation that picks the smallest encoding, working within the
constraints of the register allocator's choices. The result is smaller
and easier to read encodings.
In the future, we may want to merge this pass into the relaxation pass,
or possibly fold it into the final encoding step, however for now, a
discrete pass will suffice.
Choosing smaller instruction encodings on eg. x86 is an optimization,
rather than a useful discrete setting.
Use "is_compressed" only for ISAs that have an explicit compression feature
that users of the output may to be aware of, such as RISC-V's RVC or
ARM's Thumb-2.
This adds a "colocated" flag to function and symbolic global variables which
indicates that they are defined along with the current function, so they can
use PC-relative addressing.
This also changes the function decl syntax; the name now always precedes the
signature, and the "function" keyword is no longer included.
