This CL adds grammar support for function pointers to generic builtins.
It also instantiates generic specializations when they are only used
in an assignment to a function pointer.

Example:

builtin GenericBuiltinTest<T: type>(c: Context, param: T): Object {
  return Null;
}

let fnptr: builtin(Context, Smi) => Object = GenericBuiltinTest<Smi>;

Change-Id: Ib7e5f47ffc05f14eb5d0b789936587263dfb961d
Reviewed-on: https://chromium-review.googlesource.com/1068731
Commit-Queue: Simon Zünd <szuend@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53284}

Change-Id: I79e4ad1cf41ea8888bf6288690203d746a7b7864
Reviewed-on: https://chromium-review.googlesource.com/1065811Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Théotime Grohens <theotime@google.com>
Cr-Commit-Position: refs/heads/master@{#53245}

This CL adds the new type expression
builtin(Context, ArgType1, ...) => ReturnType
and allows to use Torque-defined builtins as values of this type, as well
as calling values of this type.
The new function pointer types are subtypes of Code.

Change-Id: Ib7ba3ce6ef7a8591a4c79230dd189fd25698d5b9
Reviewed-on: https://chromium-review.googlesource.com/1060056
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53217}

Including specialization, e.g.:

  // Declare parameterized generic
  macro GenericMacroTest<T: type>(param: T): Object {
    return Undefined;
  }

  // Declare specialization of generic
  GenericMacroTest<Object>(param: Object): Object {
    return param;
  }

  ...
  assert(GenericMacroTest<Smi>(0) == Undefined);
  assert(GenericMacroTest<Smi>(1) == Undefined);
  assert(GenericMacroTest<Object>(Null) == Null);
  assert(GenericMacroTest<Object>(False) == False);
  ...

Known issue: specialization doesn't rigorously checked to verify
that specialization signature precisely matches generic declaration.

Change-Id: I9d9d96da4c5c8c9a76550844680e9e133a5edaed
Reviewed-on: https://chromium-review.googlesource.com/1043986
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53203}

This CL changes the generated C++ code for LabeledStatementBlocks to
only emit labels if they are used.

Prior to this CL, when a label was only used on one path of an
if constexpr expression, and not at all anywhere else,
the try/label construct would BIND a label that was not used,
causing a CSA verification error.

R=tebbi@chromium.org

Change-Id: Ia81a0cd081b84528c95bbdbdb98b9ab51928e13f
Reviewed-on: https://chromium-review.googlesource.com/1057247Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Simon Zünd <szuend@google.com>
Cr-Commit-Position: refs/heads/master@{#53173}

Change-Id: I37ed9115c099f3d17f23a26348a1bbf5f773ee32
Reviewed-on: https://chromium-review.googlesource.com/1056668Reviewed-by: Daniel Clifford <danno@chromium.org>
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Cr-Commit-Position: refs/heads/master@{#53136}

In the process, add a few simple tests for "constexpr" expressions, which
identified a few bugs that are also fixed in this CL.

Change-Id: I97486c781572642d2b574b92133b1f9cda3db592
Reviewed-on: https://chromium-review.googlesource.com/1055493
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53135}