[PATCH] D151457: [TableGen] Add !getdagargs and !getdagnames

[Michael Liao via Phabricator via llvm-commits]

hliao added inline comments.


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Comment at: llvm/docs/TableGen/ProgRef.rst:1718-1720
+    from the given *dag* node. Due to limitations of the type system, if not
+    all arguments are not of the specified type or derived from the specified
+    base class, an error is reported. However, ``?`` is allowed.
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simon_tatham wrote:
> That seems quite restrictive – it means this system can't be used at all in any context where the arguments to a dag are intentionally heterogeneous.
> 
> A couple of possible alternatives:
> 
> 1. Make `!getdagargs<T>(dag)` return `?` without error for each argument whose type isn't `T` or a subtype.
> 
> 2. Instead of an operator to fetch all the arguments at once, have an operator to fetch just one at a time, say `!getdagarg<T>(dag, index)`. Then if I have a dag operator that always expects a Foo and a Bar, I can call `!getdagarg<Foo>(d, 0)` and `!getdagarg<Bar>(d, 1)`.
> 
> With option 2, if there were also an operator to return the //number// of arguments, then you could still get a list of all of them using `!foreach`.
Yes, for completeness, `!getdagarg(arg, name)` and `!getdagarg(arg, idx)` (without casting to `T`) are the 2nd part I was preparing together with `!getdagname(arg, idx)`.
I will update the patch to allow arguments with non-common type returned as `?`.


Repository:
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  https://reviews.llvm.org/D151457/new/

https://reviews.llvm.org/D151457