[PATCH] D77923: OpenCL: Fix some missing predefined macros

[Matt Arsenault via Phabricator via cfe-commits]

arsenm added a comment.

In D77923#1979286 <https://reviews.llvm.org/D77923#1979286>, @jvesely wrote:

> > In D77923#1976497 <https://reviews.llvm.org/D77923#1976497>, @jvesely wrote:
> > 
> >> OPENCL_VERSION is something that should be really set by the opencl driver rather than the compiler.
> >>  coarse-grained SVM can be done without FEATURE_FLAT_ADDRESS_SPACE, so those gpus can get over 1.2, while the compiler can be used in an implementation that doesn't go above 1.2 even for gfx700+
> > 
> > 
> > I don't know why this would imply we can't just have a static `__OPENCL_VERSION__` for each device in Clang? I don't see anything in the standard that says you are not allowed to have (going with your example) `__OPENCL_VERSION__=200` and `__OPENCL_C_VERSION=120` at the same time.
> > 
> > It seems like we should be able to just have `__OPENCL_VERSION__` defined in Clang, and let the runtime control setting `__OPENCL_C_VERSION__` via `-cl-std=`. If the current patch sets `__OPENCL_VERSION__` differently than the runtime does then it seems like we should make it match, but I'm not sure how best to confirm that.
>
> The `__OPENCL_VERSION__` macro in the kernel needs to match the version returned by `clGetDeviceInfo` (both refer to OpenCL version supported by the device),
>  which in turn must be <= version returned by `clGetPlatformInfo`.
>  This part makes it unsuitable for hardcoding in the compiler.
>
> `__OPENCL_VERSION__` should indicate device capabilities rather than language features. specs talk about available resources.
>  For example, `CL_DEVICE_IMAGE2D_MAX_HEIGHT` is required to be >= 8192 for OpenCL 1.2 while it's required to be >=16384 for OpenCL 2.1.


But why would the driver not report the device values which we do know in the compiler? A discrepancy between these sounds like a driver bug.

> if there's to be a default value hardcoded in the compiler it'd be nice if platform drivers had an easy way to override (lower) it.

I found a hacky way to do this. You can -include a header, which happens after the predefines, with undef and redef of the predefined value. This does trigger -Wreserved-id-macro (which I only found through -Weverything), but you should be able to pragma push/pop the warning off inside the special header.

For now I could assume the platform is 2.0 based on -amdhsa, and not for -mesa3d to work around clover not currently supporting CL2.0.


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