This enables thunking to work when the function has `ref` parameters,
without jumping through hoops to add `ref` tags in the desugared
function body.
This also renames `is_operator_syntax` to `is_desugared`, which is more
general and more accurate.
- A function with a return declaration always has exactly one
`ReturnSlotPattern`, representing the whole return declaration (whereas
previously that was omitted for value and reference returns).
- The `ReturnSlotPattern` always has a subpattern with the same form.
`OutParamPattern` already plays that role for initializing forms, and
`TuplePattern` will play that role for tuple forms. This change
introduces `ValueReturnPattern` and `RefReturnPattern` to represent
value and reference return forms.
- As before, the `ReturnSlotPattern` has a corresponding `ReturnSlot`
that represents the output that is initialized by a `return` statement.
Its structure parallels the structure of the `ReturnSlotPattern`, so we
need `ValueReturn` and `RefReturn` insts that correspond to
`ValueReturnPattern` and `RefReturnPattern`.
This is a step toward supporting generic return forms, where the
`ReturnSlotPattern`'s subpattern may be an action: this change ensures
that evaluating the action for a specific form produces the same SemIR
as if the form were concrete to begin with. More speculatively, this
should simplify the implementation of `return` statements with compound
return forms.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
For calling non-`()` functions, the Carbon->Carbon thunk now takes an
extra reference parameter and writes the target function's return value
out to that parameter. (At the SemIR level this is how returns already
work, but adding this extra reference parameter is needed so that the
function is lowered correctly.) The C++ thunk now creates a local
variable to be initialized by the Carbon thunk, and then returns that
value to the original C++ caller.
This makes the thunk-call logic more general and more supportable by
reusing the existing pattern-matching logic.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
`ReturnTypeInfo` is built around the assumption that a function call
results in exactly one initializing expression, but with `ref` returns
there may be zero, and in the future composite return forms will enable
there to be more than one. This change removes some usages of
`ReturnTypeInfo`, and restructures the calling code to be prepared for
multiple initializing returns.
This separates the return type from the return pattern, and replaces the
return pattern with a block of return patterns. This is a step toward
support for `ref` returns (where there's no corresponding return
pattern) and compund-form returns (where there may be multiple return
patterns).
This is a followup from #4834, I searched for "invalid" uses in our
codebase. This is mostly changing comments, and a couple debug
functions, but shouldn't affect testable behavior.
Note a couple things I'll highlight as not changing (but could) are:
- `ReturnTypeInfo::is_valid`
- `"invalid"` uses in the formatter
- `AddInvalid` for `!has_value` in `inst_fingerprinter` (because the
cases it's called sound invalid-ish)
This introduces `calling_convention_param_ids`, a single block that
consolidates all the information that was being used by consumers of
`param_refs` and `implicit_param_refs`, in a form that's easier to
produce and typically easier to consume.
See also [this Discord
discussion](https://discord.com/channels/655572317891461132/655578254970716160/1300545448909738125)
regarding the decision to keep the return slot last in the SemIR calling
convention, even though it goes first in the LLVM calling convention.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Also propagate the pattern IR along with the pattern-match IR, and use
it where appropriate.
Strictly speaking, some parts of the pattern-match IR are allocated
eagerly, while traversing the pattern's parse tree, but they still
aren't actually emitted until we traverse the associated pattern insts.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Geoff Romer
Nicholas Bishop
