Codegen support for reduction over private variable with reduction
clause. Section 7.6.10 in in OpenMP 6.0 spec.
- An internal shared copy is initialized with an initializer value.
- The shared copy is updated by combining its value with the values from
the private copies created by the clause.
- Once an encountering thread verifies that all updates are complete,
its original list item is updated by merging its value with that of the
shared copy and then broadcast to all threads.
Sample Test Case from OpenMP 6.0 Example
```
#include <assert.h>
#include <omp.h>
#define N 10
void do_red(int n, int *v, int &sum_v)
{
sum_v = 0; // sum_v is private
#pragma omp for reduction(original(private),+: sum_v)
for (int i = 0; i < n; i++)
{
sum_v += v[i];
}
}
int main(void)
{
int v[N];
for (int i = 0; i < N; i++)
v[i] = i;
#pragma omp parallel num_threads(4)
{
int s_v; // s_v is private
do_red(N, v, s_v);
assert(s_v == 45);
}
return 0;
}
```
Expected Codegen:
```
// A shared global/static variable is introduced for the reduction result.
// This variable is initialized (e.g., using memset or a UDR initializer)
// e.g., .omp.reduction.internal_private_var
// Barrier before any thread performs combination
call void @__kmpc_barrier(...)
// Initialization block (executed by thread 0)
// e.g., call void @llvm.memset.p0.i64(...) or call @udr_initializer(...)
call void @__kmpc_critical(...)
// Inside critical section:
// Load the current value from the shared variable
// Load the thread-local private variable's value
// Perform the reduction operation
// Store the result back to the shared variable
call void @__kmpc_end_critical(...)
// Barrier after all threads complete their combinations
call void @__kmpc_barrier(...)
// Broadcast phase:
// Load the final result from the shared variable)
// Store the final result to the original private variable in each thread
// Final barrier after broadcast
call void @__kmpc_barrier(...)
```
---------
Co-authored-by: Chandra Ghale <ghale@pe31.hpc.amslabs.hpecorp.net>
Initial Parse/Sema support for reduction over private variable with
reduction clause.
Section 7.6.10 in in OpenMP 6.0 spec.
- list item in a reduction clause can now be private in the enclosing
context.
- Added support for _original-sharing-modifier_ with reduction clause.
---------
Co-authored-by: Chandra Ghale <ghale@pe31.hpc.amslabs.hpecorp.net>
Currently, clang gives an incorrect reduction identifier error for the PLUS
operator for OpenMP version > 52. But, PLUS operator is allowed in OpenMP
version > 52. This revision fixes this issue and also modified the error
messages to show the correct expected operators in the message based on the OpenMP
version used (prior to OMP 6.0 and since OMP 6.0).
Test Src:
void foo() {
int a = 0 ;
#pragma omp parallel reduction(+:a)
;
#pragma omp parallel reduction(-:a)
;
}
Before this revision:
$ clang -fopenmp -fopenmp-version=60 test.c -c
test.c:3:34: error: incorrect reduction identifier, expected one of '+', '-', '*', '&', '|', '^', '&&', '||', 'min' or 'max' or declare reduction for type 'int'
3 | #pragma omp parallel reduction(+:a)
| ^
test.c:5:34: error: incorrect reduction identifier, expected one of '+', '-', '*', '&', '|', '^', '&&', '||', 'min' or 'max' or declare reduction for type 'int'
5 | #pragma omp parallel reduction(-:a)
| ^
2 errors generated.
Wit this revision:
$ clang -fopenmp -fopenmp-version=60 test.c -c
test.c:5:34: error: incorrect reduction identifier, expected one of '+', '*', '&', '|', '^', '&&', '||', 'min' or 'max' or declare reduction for type 'int'
5 | #pragma omp parallel reduction(-:a)
|
1 error generated.
Differential Revision: https://reviews.llvm.org/D155635
The default version of OpenMP is updated from 5.0 to 5.1 which means if -fopenmp is specified but -fopenmp-version is not specified with clang, the default version of OpenMP is taken to be 5.1. After modifying the Frontend for that, various LIT tests were updated. This patch contains all such changes. At a high level, these are the patterns of changes observed in LIT tests -
# RUN lines which mentioned `-fopenmp-version=50` need to kept only if the IR for version 5.0 and 5.1 are different. Otherwise only one RUN line with no version info(i.e. default version) needs to be there.
# Test cases of this sort already had the RUN lines with respect to the older default version 5.0 and the version 5.1. Only swapping the version specification flag `-fopenmp-version` from newer version RUN line to older version RUN line is required.
# Diagnostics: Remove the 5.0 version specific RUN lines if there was no difference in the Diagnostics messages with respect to the default 5.1.
# Diagnostics: In case there was any difference in diagnostics messages between 5.0 and 5.1, mention version specific messages in tests.
# If the test contained version specific ifdef's e.g. "#ifdef OMP5" but there were no RUN lines for any other version than 5.X, then bring the code guarded by ifdef's outside and remove the ifdef's.
# Some tests had RUN lines for both 5.0 and 5.1 versions, but it is found that the IR for 5.0 is not different from the 5.1, therefore such RUN lines are redundant. So, such duplicated lines are removed.
# To generate CHECK lines automatically, use the script llvm/utils/update_cc_test_checks.py
Reviewed By: saiislam, ABataev
Differential Revision: https://reviews.llvm.org/D129635
(cherry picked from commit 9dd2999907dc791136a75238a6000f69bf67cf4e)
The OpenMP spec seems to require the compound operators be used for
+, *, &, |, and ^ reduction. So use these if a class has those operators.
If not try the simple operators as we did previously to limit the impact
to existing code.
Fixes: https://bugs.llvm.org/show_bug.cgi?id=48584
Differential Revision: https://reviews.llvm.org/D101941
Summary:
Added basic support for 'task' modifier in the reduction clauses in
non-simd parallel and worksharing constructs.
Reviewers: jdoerfert
Subscribers: yaxunl, guansong, cfe-commits, caomhin
Tags: #clang
Differential Revision: https://reviews.llvm.org/D78738
Summary:
Reduction variables are the variables, for which the private copies
must be created in the OpenMP regions. Then they are initialized with
the predefined values depending on the reduction operation. After exit
from the OpenMP region the original variable is updated using the
reduction value and the value of the original reduction variable.
Reviewers: NoQ
Subscribers: guansong, jdoerfert, caomhin, kkwli0, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D65106
llvm-svn: 367116
As discussed in D56113, this patch refactors the implementation of the
const restriction for reductions to reuse a function introduced by
D56113. A side effect is that diagnostics sometimes now say
"variable" instead of "list item" when a list item is a variable.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D56298
llvm-svn: 350440
only.
Added support for -fopenmp-simd option that allows compilation of
simd-based constructs without emission of OpenMP runtime calls.
llvm-svn: 321560
If the member declaration is captured in the OMPCapturedExprDecl, we may
loose data-sharing attribute info for this declaration. Patch fixes this
bug.
llvm-svn: 308629
OpenMP 4.0 allows to define custom reduction operations using '#pragma
omp declare reduction' construct. Patch allows to use this custom
defined reduction operations in 'reduction' clauses.
llvm-svn: 263701
-fopenmp turns on OpenMP support and links libiomp5 as OpenMP library. Also there is -fopenmp={libiomp5|libgomp} option that allows to override effect of -fopenmp and link libgomp library (if -fopenmp=libgomp is specified).
Differential Revision: http://reviews.llvm.org/D9736
llvm-svn: 237769
Currently checks for active data-sharing attributes for variables are performed for found var decls. Instead these checks must be performed for canonical decls of these variables to avoid possible troubles with with the differently qualified re-declarations of the same variable, for example:
namespace A { int x; }
namespace B { using A::x; }
Both A::x and B::x actually reference the same object A::x and this fact must be taken into account during data-sharing attributes analysis.
llvm-svn: 235096
