[flang][openacc] Lower acc cache directive (#65673)

The cache directive is attached directly to the acc.loop operation when the directive appears in the loop. When it appears before a loop, the OpenACCCacheConstruct is saved and attached when the acc.loop is created. Directive that cannot be attached to a loop are silently discarded. Depends on #65521

Author: clementval

flang/lib/Lower/OpenACC.cpp

@@ -3096,6 +3096,41 @@ void Fortran::lower::finalizeOpenACCRoutineAttachment(
  accRoutineInfos.clear();
 }
 
+static void
+genACC(Fortran::lower::AbstractConverter &converter,
+ Fortran::semantics::SemanticsContext &semanticsContext,
+ const Fortran::parser::OpenACCCacheConstruct &cacheConstruct) {
+ fir::FirOpBuilder &builder = converter.getFirOpBuilder();
+ auto loopOp = builder.getRegion().getParentOfType<mlir::acc::LoopOp>();
+ auto crtPos = builder.saveInsertionPoint();
+ if (loopOp) {
+ builder.setInsertionPoint(loopOp);
+ Fortran::lower::StatementContext stmtCtx;
+ llvm::SmallVector<mlir::Value> cacheOperands;
+ const Fortran::parser::AccObjectListWithModifier &listWithModifier =
+ std::get<Fortran::parser::AccObjectListWithModifier>(cacheConstruct.t);
+ const auto &accObjectList =
+ std::get<Fortran::parser::AccObjectList>(listWithModifier.t);
+ const auto &modifier =
+ std::get<std::optional<Fortran::parser::AccDataModifier>>(
+ listWithModifier.t);
+
+ mlir::acc::DataClause dataClause = mlir::acc::DataClause::acc_cache;
+ if (modifier &&
+ (*modifier).v == Fortran::parser::AccDataModifier::Modifier::ReadOnly)
+ dataClause = mlir::acc::DataClause::acc_cache_readonly;
+ genDataOperandOperations<mlir::acc::CacheOp>(
+ accObjectList, converter, semanticsContext, stmtCtx, cacheOperands,
+ dataClause,
+ /*structured=*/true, /*implicit=*/false, /*setDeclareAttr*/ false);
+ loopOp.getCacheOperandsMutable().append(cacheOperands);
+ } else {
+ llvm::report_fatal_error(
+ "could not find loop to attach OpenACC cache information.");
+ }
+ builder.restoreInsertionPoint(crtPos);
+}
+
 void Fortran::lower::genOpenACCConstruct(
  Fortran::lower::AbstractConverter &converter,
  Fortran::semantics::SemanticsContext &semanticsContext,
@@ -3119,8 +3154,7 @@ void Fortran::lower::genOpenACCConstruct(
  genACC(converter, semanticsContext, standaloneConstruct);
  },
  [&](const Fortran::parser::OpenACCCacheConstruct &cacheConstruct) {
- TODO(converter.genLocation(cacheConstruct.source),
- "OpenACC Cache construct not lowered yet!");
+ genACC(converter, semanticsContext, cacheConstruct);
  },
  [&](const Fortran::parser::OpenACCWaitConstruct &waitConstruct) {
  genACC(converter, waitConstruct);

flang/test/Lower/OpenACC/acc-loop.f90

@@ -305,4 +305,13 @@ program acc_loop
 !CHECK: acc.yield
 !CHECK-NEXT: }{{$}}
 
+ !$acc loop
+ DO i = 1, n
+ !$acc cache(b)
+ a(i) = b(i)
+ END DO
+
+! CHECK: %[[CACHE:.*]] = acc.cache varPtr(%{{.*}} : !fir.ref<!fir.array<10xf32>>) bounds(%{{.*}}) -> !fir.ref<!fir.array<10xf32>> {name = "b"}
+! CHECK: acc.loop cache(%[[CACHE]] : !fir.ref<!fir.array<10xf32>>)
+
 end program