[PATCH] D78655: [HIP] Let lambda be host device by default

[Michael Liao via Phabricator via cfe-commits]

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In D78655#1997491 <https://reviews.llvm.org/D78655#1997491>, @tra wrote:

> Summoning @rsmith as I'm sure that there are interesting corner cases in lambda handling that we didn't consider.
>
> Making lambdas implicitly HD will make it easier to write the code which can't be instantiated on one side of the compilation. That's probably observable via SFINAE, but I can't tell whether that matters.
>  By default I'd rather err on handling lambdas the same way as we do regular user-authored functions.


Marking lambda `__device__`/`__device__ __host__` should be

In D78655#1997491 <https://reviews.llvm.org/D78655#1997491>, @tra wrote:

> Summoning @rsmith as I'm sure that there are interesting corner cases in lambda handling that we didn't consider.
>
> Making lambdas implicitly HD will make it easier to write the code which can't be instantiated on one side of the compilation. That's probably observable via SFINAE, but I can't tell whether that matters.
>  By default I'd rather err on handling lambdas the same way as we do regular user-authored functions.


Marking lambda with proper attributes helps check the potential harmful captures.

In D78655#1997491 <https://reviews.llvm.org/D78655#1997491>, @tra wrote:

> Summoning @rsmith as I'm sure that there are interesting corner cases in lambda handling that we didn't consider.
>
> Making lambdas implicitly HD will make it easier to write the code which can't be instantiated on one side of the compilation. That's probably observable via SFINAE, but I can't tell whether that matters.
>  By default I'd rather err on handling lambdas the same way as we do regular user-authored functions.


I though the goal of adding HD/D attributes for lambda is to make the static check easier as lambda used in device code or device lambda is sensitive to captures. Invalid capture may render error accidentally without static check, says we capture host variable reference in a device lambda. That makes the final code invalid. Allowing regular lambda to be used in global or device function is considering harmful.


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https://reviews.llvm.org/D78655