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

Change-Id: I884f7f16a467ab716d2b0c553485f4b1c55ed806
Reviewed-on: https://chromium-review.googlesource.com/1063613Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53252}

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}

Change-Id: I61a594e194082577135dbc82b2673bf477105ef3
Reviewed-on: https://chromium-review.googlesource.com/1046949
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53050}

Torque expressions of type constexpr are evaluated at compile-time
rather than runtime. They are backed by C++ types rather than
TNode<X> types, so the macro functions that are called by generated
C++ code expect values to be computed when the snapshot is generated
rather than by TurboFan-generated code.

Specifically, "if" statements can have a constexpr modifier. With this
modifier, a type of "constexpr bool" is expected rather than "bool",
and in that case instead of generating a CSA BranchIf, it generates
a C++ "if (<bool expression>)" that generates code for only the true or
false path based on the bool value at torque-execution (compile time)
rather than generating both paths (including inserting phi nodes
for variables modified on either branch at the re-merge at the end
of the if) and dynamically dispatching to the true or false path
during d8/Chrome/node.js execution (runtime) using a CSA BranchIf.

Change-Id: I8238e25aaadbfc618847e04556e96a3949ea5a8d
Reviewed-on: https://chromium-review.googlesource.com/1042085
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53001}

This is a preparatory step for implementing generics. Along the way, clean up
and encapsulate a bunch of code, including:

* Fully encapsulate Scope by adding the new class ScopeChain that provide an
  abstraction for creating and activating scopes.
* Untangle Modules and Scopes.
* Unify scope activation so that it is always associated with an AST node
  and triggered by a RAII helper class.
* Unify (somewhat) how builtins and macros are created, fixing a few
  inconsistencies with when and how parameters and their types are declared.
* Create a new Declarations class that brokers between the visitor classes and
  the ScopeChain. This moves handling of declaration-related errors out of the
  visitors but also makes it possible to do so without polluting Scope and
  ScopeChain with details about resolving SourcePositions in error cases.

Change-Id: I180017d4cf39ccf5ef1d20b84f53284c252f8d87
Reviewed-on: https://chromium-review.googlesource.com/1038504
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52947}

Bug: v8:7666
Change-Id: Ida9b6f964261bad75a4eb5d567ad37ec82569bcc
Reviewed-on: https://chromium-review.googlesource.com/1023061
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52751}

An overview of motivation behind Torque and some of its principles
can be found here: https://bit.ly/2qAI5Ep

Note that there is quite a bit of work left to do in order to get
Torque production-ready for any non-trivial amount of code, but
landing the prototype as-is will allow for much faster iteration.

Bugs will be filed for all of the big-ticket items that are not
landing blockers but called out in this patch as important to fix.

Cq-Include-Trybots: luci.v8.try:v8_linux_nosnap_rel;luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: Ib07af70966d5133dc57344928885478b9c6b8b73
Reviewed-on: https://chromium-review.googlesource.com/845682
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52618}