[flang-commits] [flang] [flang][OpenMP] Move privatizations out of sections (PR #88191)

[Krzysztof Parzyszek via flang-commits]

================
@@ -1983,30 +1980,68 @@ genOMP(Fortran::lower::AbstractConverter &converter,
         std::get<Fortran::parser::OmpEndSectionsDirective>(sectionsConstruct.t);
     const auto &endSectionsClauseList =
         std::get<Fortran::parser::OmpClauseList>(endSectionsDirective.t);
-    ClauseProcessor(converter, semaCtx, endSectionsClauseList)
-        .processNowait(nowaitClauseOperand);
+    hasNowait = ClauseProcessor(converter, semaCtx, endSectionsClauseList)
+                    .processNowait(nowaitClauseOperand);
   }
 
+  // Insert privatizations before SECTIONS
+  symTable.pushScope();
+  DataSharingProcessor dsp(converter, semaCtx, sectionsClauseList, eval);
+  dsp.processStep1();
+
   // SECTIONS construct
-  genOpWithBody<mlir::omp::SectionsOp>(
+  auto sectionsOp = genOpWithBody<mlir::omp::SectionsOp>(
       OpWithBodyGenInfo(converter, semaCtx, currentLocation, eval)
           .setGenNested(false),
       /*reduction_vars=*/mlir::ValueRange(),
       /*reductions=*/nullptr, allocateOperands, allocatorOperands,
       nowaitClauseOperand);
 
+  std::optional<Clause> lastPrivateClause;
+  for (const Fortran::parser::OmpClause &clause : sectionsClauseList.v) {
+    if (std::holds_alternative<Fortran::parser::OmpClause::Lastprivate>(
+            clause.u)) {
+      lastPrivateClause = makeClause(clause, semaCtx);
+    }
+  }
+
   const auto &sectionBlocks =
       std::get<Fortran::parser::OmpSectionBlocks>(sectionsConstruct.t);
   auto &firOpBuilder = converter.getFirOpBuilder();
   auto ip = firOpBuilder.saveInsertionPoint();
-  for (const auto &[nblock, neval] :
-       llvm::zip(sectionBlocks.v, eval.getNestedEvaluations())) {
-    symTable.pushScope();
-    genSectionOp(converter, semaCtx, neval, /*genNested=*/true, currentLocation,
-                 sectionsClauseList);
-    symTable.popScope();
+  auto zippy = llvm::zip(sectionBlocks.v, eval.getNestedEvaluations());
+  auto it = zippy.begin(), next = it, end = zippy.end();
+  ++next;
+  for (; it != end; it = next, ++next) {
+    const auto &[nblock, neval] = *it;
+    mlir::omp::SectionOp sectionOp = genSectionOp(
+        converter, semaCtx, neval, /*genNested=*/true, currentLocation);
+    // For `omp.sections`, lastprivatized variables occur in
+    // lexically final `omp.section` operation.
+    if (next == end && lastPrivateClause) {
----------------
kparzysz wrote:

This code doesn't need to be in the loop that creates section ops.  You can just create all section ops, and only remember the most recently created SectionOp.  Then after the loop, if lastprivate was present, insert the copying code.

https://github.com/llvm/llvm-project/pull/88191