[OpenMP] Limit reduction support for pragma 'distribute' when combined with pragma 'simd'

[carlo.bertolli]

Summary

This is a bug fix that removes the emission of reduction support for pragma 'distribute' when found alone or in combinations without simd.
Pragma 'distribute' does not have a reduction clause, but when combined with pragma 'simd' we need to emit the support for simd's reduction clause as part of code generation for distribute. This guard is similar to the one used for reduction support earlier in the same code gen function.

[ABataev]

Tests?

[carlo.bertolli]

[OpenMP] Add regression test: this verifies that only one call to the runtime for reduction is done in a combined construct with distribute, without simd, and with at least one pragma accepting reduction as a clause.

[ABataev]

LG

lib/CodeGen/CGStmtOpenMP.cpp

// Emit 'then' code.
                                    CodeGenLoop);
       }
       if (isOpenMPSimdDirective(S.getDirectiveKind())) {
         EmitOMPSimdFinal(S, [&](CodeGenFunction &CGF) -> llvm::Value * {
           return CGF.Builder.CreateIsNotNull(
               CGF.EmitLoadOfScalar(IL, S.getLocStart()));
         });
       }
+      if (isOpenMPSimdDirective(S.getDirectiveKind()) &&
+          !isOpenMPParallelDirective(S.getDirectiveKind()) &&
+          !isOpenMPTeamsDirective(S.getDirectiveKind())) {
         OpenMPDirectiveKind ReductionKind = OMPD_unknown;
         if (isOpenMPParallelDirective(S.getDirectiveKind()) &&
             isOpenMPSimdDirective(S.getDirectiveKind())) {
           ReductionKind = OMPD_parallel_for_simd;
         } else if (isOpenMPParallelDirective(S.getDirectiveKind())) {
           ReductionKind = OMPD_parallel_for;
         } else if (isOpenMPSimdDirective(S.getDirectiveKind())) {
           ReductionKind = OMPD_simd;
         } else if (!isOpenMPTeamsDirective(S.getDirectiveKind()) &&
                    S.hasClausesOfKind<OMPReductionClause>()) {
           llvm_unreachable(
               "No reduction clauses is allowed in distribute directive.");
         }
         EmitOMPReductionClauseFinal(S, ReductionKind);
         // Emit post-update of the reduction variables if IsLastIter != 0.
         emitPostUpdateForReductionClause(
             *this, S, [&](CodeGenFunction &CGF) -> llvm::Value * {
               return CGF.Builder.CreateIsNotNull(
                   CGF.EmitLoadOfScalar(IL, S.getLocStart()));
             });
+      }
       // Emit final copy of the lastprivate variables if IsLastIter != 0.
       if (HasLastprivateClause) {
         EmitOMPLastprivateClauseFinal(
             S, /*NoFinals=*/false,
             Builder.CreateIsNotNull(EmitLoadOfScalar(IL, S.getLocStart())));
       }
     }
 

test/OpenMP/distribute_parallel_for_reduction_codegen.cpp

+// Test host code gen
+
+// RUN: %clang_cc1  -verify -fopenmp -fopenmp-version=45 -x c++ -std=c++11 -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-llvm %s -o - | FileCheck %s --check-prefix CHECK --check-prefix CHECK-64
+// RUN: %clang_cc1  -fopenmp -fopenmp-version=45 -x c++ -std=c++11 -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-pch -o %t %s
+// RUN: %clang_cc1  -fopenmp -fopenmp-version=45 -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck %s --check-prefix CHECK --check-prefix CHECK-64
+// RUN: %clang_cc1  -verify -fopenmp -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm %s -o - | FileCheck %s --check-prefix CHECK --check-prefix CHECK-32
+// RUN: %clang_cc1  -fopenmp -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-pch -o %t %s
+// RUN: %clang_cc1  -fopenmp -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck %s --check-prefix CHECK --check-prefix CHECK-32
+
+// RUN: %clang_cc1  -verify -fopenmp-simd -fopenmp-version=45 -x c++ -std=c++11 -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-llvm %s -o - | FileCheck --check-prefix SIMD-ONLY1 %s
+// RUN: %clang_cc1  -fopenmp-simd -fopenmp-version=45 -x c++ -std=c++11 -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -emit-pch -o %t %s
+// RUN: %clang_cc1  -fopenmp-simd -fopenmp-version=45 -x c++ -triple powerpc64le-unknown-unknown -fopenmp-targets=powerpc64le-ibm-linux-gnu -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck --check-prefix SIMD-ONLY1 %s
+// RUN: %clang_cc1  -verify -fopenmp-simd -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-llvm %s -o - | FileCheck --check-prefix SIMD-ONLY1 %s
+// RUN: %clang_cc1  -fopenmp-simd -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -emit-pch -o %t %s
+// RUN: %clang_cc1  -fopenmp-simd -fopenmp-version=45 -x c++ -std=c++11 -triple i386-unknown-unknown -fopenmp-targets=i386-pc-linux-gnu -std=c++11 -include-pch %t -verify %s -emit-llvm -o - | FileCheck --check-prefix SIMD-ONLY1 %s
+// SIMD-ONLY1-NOT: {{__kmpc|__tgt}}
+// expected-no-diagnostics
+#ifndef HEADER
+#define HEADER
+
+
+template <typename T>
+T tmain(T &r) {
+  int n = 1000;  
+  // schedule: dynamic chunk
+  #pragma omp target map(tofrom:r)
+  #pragma omp teams
+  #pragma omp distribute parallel for reduction(+:r)
+  for (int i = 0; i < n; ++i)
+    r += (T)i;  
+
+  return r;
+}
+
+int main() {
+  int n = 1000;
+  int r = 0;
+  #pragma omp target map(tofrom:r)
+  #pragma omp teams
+  #pragma omp distribute parallel for reduction(+:r)
+  for (int i = 0; i < n; ++i)
+    r += i;
+
+  return tmain<int>(r);
+}
+
+// CHECK-LABEL: main
+// CHECK: call{{.+}} @__tgt_target_teams(
+// CHECK: call void [[OFFL:@.+]](
+// CHECK: call{{.+}} [[TMAIN:@.+]](i{{32|64}}
+// CHECK: ret
+
+// CHECK: define{{.+}} [[OFFL]](
+// CHECK: call{{.+}} @__kmpc_fork_teams({{.+}}, {{.+}}, {{.+}} [[TEOUTL:@.+]] to{{.+}}
+// CHECK: ret void
+
+// CHECK: define{{.+}} [[TEOUTL]](
+// CHECK: call{{.+}} @__kmpc_fork_call({{.+}}, {{.+}}, {{.+}} [[PAROUTL:@.+]] to{{.+}}
+// CHECK: ret void
+
+// CHECK: define{{.+}} [[PAROUTL]](
+// CHECK: call{{.+}} @__kmpc_reduce_nowait(
+// CHECK: call{{.+}} @__kmpc_end_reduce_nowait(
+// CHECK: ret void
+
+// CHECK: define{{.+}} [[TMAIN]](i{{32|64}}
+// CHECK: call{{.+}} @__tgt_target_teams(
+// CHECK: call void [[TOFFL:@.+]](
+// CHECK: ret
+
+// CHECK: define{{.+}} [[TOFFL]](
+// CHECK: call{{.+}} @__kmpc_fork_teams({{.+}}, {{.+}}, {{.+}} [[TEMPLTEOUTL:@.+]] to{{.+}}
+// CHECK: ret void
+
+// CHECK: define{{.+}} [[TEMPLTEOUTL]](
+// CHECK: call{{.+}} @__kmpc_fork_call({{.+}}, {{.+}}, {{.+}} [[TPAROUTL:@.+]] to{{.+}}
+// CHECK: ret void
+
+// CHECK: define{{.+}} [[TPAROUTL]](
+// CHECK: call{{.+}} @__kmpc_reduce_nowait(
+// CHECK: call{{.+}} @__kmpc_end_reduce_nowait(
+// CHECK: ret void
+
+#endif // HEADER