llvm-project/clang/test/OpenMP/nvptx_parallel_num_threads_strict_messages.cpp
Robert Imschweiler 814a3a6b61
[OpenMP][clang] Set num_threads 'strict' to unsupported on GPUs (#160659)
Setting the prescriptiveness of the num_threads clause to 'strict' and
having a corresponding check (with message and severity clauses) does
not align well with how OpenMP should be handled for GPUs.

The num_threads expression may be an arbitrary integer expression which
is evaluated on the target, in correspondance to the OpenMP spec. This
prevents the check from being done before launching the kernel,
especially considering that the num_threads clause is associated with
the parallel directive and that there may be multiple parallel
directives with different num_threads clauses in a single target region.
Acting on the result of the 'strict' check on the GPU would require
doing I/O on the GPU, which can introduce performance regressions.
Delaying any actions resulting from the 'strict' check and doing them on
the host after executing the target region involves additional data
copies and is not really semantically correct.

For now, the 'strict' modifier for the num_threads clause and its
associated message and severity clause are set to be unsupported on
GPUs. Targets other than GPUs still support the aforementioned features
in the context of an OpenMP target region.
2025-09-26 13:50:18 -05:00

109 lines
3.2 KiB
C++

// RUN: %clang_cc1 -DF1 -verify -fopenmp -fopenmp-version=60 -triple x86_64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm-bc %s -o %t-ppc-host-ppc.bc
// RUN: %clang_cc1 -DF1 -DTARGET -verify -fopenmp -fopenmp-version=60 -triple nvptx64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm %s -fopenmp-is-target-device -fopenmp-host-ir-file-path %t-ppc-host-ppc.bc -o /dev/null
// RUN: %clang_cc1 -DF2 -verify -fopenmp -fopenmp-version=60 -triple x86_64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm-bc %s -o %t-ppc-host-ppc.bc
// RUN: %clang_cc1 -DF2 -DTARGET -verify -fopenmp -fopenmp-version=60 -triple nvptx64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm %s -fopenmp-is-target-device -fopenmp-host-ir-file-path %t-ppc-host-ppc.bc -o /dev/null
// RUN: %clang_cc1 -DF3 -verify -fopenmp -fopenmp-version=60 -triple x86_64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm-bc %s -o %t-ppc-host-ppc.bc
// RUN: %clang_cc1 -DF3 -DTARGET -verify -fopenmp -fopenmp-version=60 -triple nvptx64-unknown-unknown -fopenmp-targets=nvptx64-nvidia-cuda -emit-llvm %s -fopenmp-is-target-device -fopenmp-host-ir-file-path %t-ppc-host-ppc.bc -o /dev/null
#ifndef TARGET
// expected-no-diagnostics
#endif
#ifdef F3
template<typename tx>
tx ftemplate(int n) {
tx a = 0;
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp parallel num_threads(strict: tx(20)) severity(fatal) message("msg")
{
}
short b = 1;
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp parallel num_threads(strict: b) severity(warning) message("msg")
{
a += b;
}
return a;
}
#endif
#ifdef F2
static
int fstatic(int n) {
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp target parallel num_threads(strict: n) message("msg")
{
}
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp target parallel num_threads(strict: 32+n) severity(warning)
{
}
return n+1;
}
#endif
#ifdef F1
struct S1 {
double a;
int r1(int n){
int b = 1;
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp parallel num_threads(strict: n-b) severity(warning) message("msg")
{
this->a = (double)b + 1.5;
}
#ifdef TARGET
// expected-warning@+2 {{modifier 'strict' is currently not supported on a GPU for the 'num_threads' clause; modifier ignored}}
#endif
#pragma omp parallel num_threads(strict: 1024) severity(fatal)
{
this->a = 2.5;
}
return (int)a;
}
};
#endif
int bar(int n){
int a = 0;
#ifdef F1
#pragma omp target
{
S1 S;
a += S.r1(n);
}
#endif
#ifdef F2
a += fstatic(n);
#endif
#ifdef F3
#pragma omp target
a += ftemplate<int>(n);
#endif
return a;
}