[llvm-dev] CUDA kernel call with template parameters not appearing in Clang AST

Justin Lebar via llvm-dev llvm-dev at lists.llvm.org
Tue Nov 28 21:07:15 PST 2017

Hi, Michael.

Are you able to create a reduced testcase which demonstrates your problem?

I tried

template <int N>
__global__ void Kernel() {}

void test() {
  Kernel<16><<<100, 200>>>();

which I compiled with

  $ clang -c -Xclang -ast-dump test.cu

and the AST looks fine to me -- the CUDAKernelCallExpr shows up as expected.


On Tue, Nov 28, 2017 at 2:33 PM Michael Ehmke via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello all,
> I'm using Clang and am trying to refactor CUDA code. I want to traverse
> the AST to access a CUDAKernelCallExpr node where the kernel call has
> template parameters. I have been able to successfully match on and access
> CUDA kernel calls which have no template parameters by using the AST
> matchers to match on a CUDAKernelCallExpr. However, when my code comes
> across a kernel call with template parameters, it appears that the
> expression is not even existent in the AST when it is dumped.
> This is the expression that I'm having trouble parsing:
> ex. matrixMulCUDA<16><<< grid, threads >>>(d_C, d_A, d_B, dimsA.x,
> dimsB.x);
> This expression does not show up at all in the AST when dumping the AST. I
> have been able to successfully parse the following kernel call expression
> and it shows up in the AST as a "CudaKernelCallExpr" node.
> ex. matrixMulCUDA<<< grid, threads >>>(d_C, d_A, d_B, dimsA.x, dimsB.x);
> As you can see, the only difference is the <16> after the name of the
> call, and this node is clearly represented in the AST.
> Here is a screenshot showing the lack of a node to represent the call with
> template parameters.
> If I could get any assistance on why this is happening, I would appreciate
> it greatly.
> Thank you,
> Michael Ehmke
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