[OMPT] Work callback does not report schedule type for loops

[Thyre]

Description

The OpenMP tools interface offers a callback called ompt_callback_work. Here, the parameter work_type can be used to determine the type of work a thread is doing. There are several different values for loops, which can be used to get the schedule for the OpenMP loops.

Right now, LLVM does not report any schedule type. Instead, the value ompt_work_loop is used for every schedule type.
From what I was able to gather in the LLVM source code, only ompt_work_loop is set and no checks for the schedule type are done:

• llvm-project/openmp/runtime/src/kmp_dispatch.cpp

  Line 1006 in 68f1391

  ompt_work_loop, ompt_scope_begin, &(team_info->parallel_data),

• llvm-project/openmp/runtime/src/kmp_sched.cpp

  Line 116 in fd2de54

  ompt_work_type = ompt_work_loop;

• llvm-project/openmp/runtime/src/kmp_csupport.cpp

  Line 1922 in fd2de54

  ompt_work_type = ompt_work_loop;

The test heaader also includes a TODO to handle the schedule types:

• llvm-project/openmp/runtime/test/ompt/callback.h

  Line 835 in fd2de54

  // TODO: add schedule attribute for the different work_loop types.

Reproducer

You can compile and run the code down below to reproduce the issue. The program will exit with an assertion error because no schedule type was reported.

$ clang --version
clang version 16.0.6 ([email protected]:llvm/llvm-project.git 7cbf1a2591520c2491aa35339f227775f4d3adf6)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/software/software/LLVM/16.0.6/bin
$ clang -fopenmp error_llvm.c
$ OMP_NUM_THREADS=1 ./a.out
ompt_work_loop detected
ompt_work_loop detected
ompt_work_loop detected
ompt_work_loop detected
ompt_work_loop detected
ompt_work_loop detected
a.out: error_llvm.c:46: void ompt_finalize(ompt_data_t *): Assertion `no_schedule == 0' failed.
[1]    609430 IOT instruction (core dumped)  OMP_NUM_THREADS=1 ./a.out

Source code:

#include <assert.h>
#include <omp.h>
#include <omp-tools.h>
#include <stdlib.h>
#include <stdio.h>

static int no_schedule = 1;

void
callback_ompt_work( ompt_work_t           work_type,
                    ompt_scope_endpoint_t endpoint,
                    ompt_data_t*          parallel_data,
                    ompt_data_t*          task_data,
                    uint64_t              count,
                    const void*           codeptr_ra )
{
    switch ( work_type )
    {
	case ompt_work_loop:
	    printf("ompt_work_loop detected\n");
	    break;
        case ompt_work_loop_static:
        case ompt_work_loop_dynamic:
        case ompt_work_loop_guided:
        case ompt_work_loop_other:
            no_schedule = 0;
            break;
        default:
            break;
    }
}

static int
ompt_initialize( ompt_function_lookup_t lookup,
                 int                    initial_device_num,
                 ompt_data_t*           tool_data )
{
    ompt_set_callback_t set_cb = ( ompt_set_callback_t )lookup( "ompt_set_callback" );
    set_cb( ompt_callback_work, ( ompt_callback_t )&callback_ompt_work );
    return 1; /* non-zero indicates success for OMPT runtime. */
}

static void
ompt_finalize( ompt_data_t* tool_data )
{
    assert(no_schedule == 0);
}

ompt_start_tool_result_t*
ompt_start_tool( unsigned int omp_version,
                 const char*  runtime_version )
{
    static ompt_start_tool_result_t ompt_start_tool_result = { &ompt_initialize,
                                                               &ompt_finalize,
                                                               ompt_data_none };
    return &ompt_start_tool_result;
}

int
main( void )
{
#pragma omp parallel for schedule(static)
    for ( unsigned i = 0; i < 100; ++i )
    {
    }

#pragma omp parallel for schedule(dynamic)
    for ( unsigned i = 0; i < 100; ++i )
    {
    }

#pragma omp parallel for schedule(guided)
    for ( unsigned i = 0; i < 100; ++i )
    {
    }

    return 0;
}

[llvmbot]

@llvm/issue-subscribers-openmp

[Thyre]

A trunk flang-new actually shows a warning not present with Clang.

OMP: Warning #189: OMPT: Cannot determine workshare type; using the default (loop) instead. This issue is fixed in an up-to-date compiler.

The second line is not true, as the issue is still present in trunk.