[Flang][OpenMP] Implementation of lowering of SIMD construct.

[arnamoy10]

Summary

This patch adds code so that using bbc we are able to see an end-to-end lowering of simd construct in action.

[arnamoy10]

Fixing the test case

[kiranchandramohan]

Looks OK. Have a few comments.

flang/lib/Lower/OpenMP.cpp

137

Nit: Can this be added to the previous if using ||?

407

Can you add Todos for the clauses or add tests for supported clauses?

flang/test/Lower/OpenMP/simd.f90

4

We are aligning with the rest of the FIR lowering tests and only testing the lowering to FIR+OpenMP dialects here. Please change this test to do just that and remove the LLVM IR check.

7

Nit: align this with rest of the code.

27

Nit: no new line.

[kiranchandramohan]

flang/test/Lower/OpenMP/simd.f90

4

Also add a FIR+OpenMP -> LLVM+OpenMP dialect test in https://github.com/llvm/llvm-project/blob/main/flang/test/Fir/convert-to-llvm-openmp-and-fir.fir

[shraiysh]

flang/lib/Lower/OpenMP.cpp

407

If D125302 gets merged before this, please add tests for collapse too.

[peixin]

flang/lib/Lower/OpenMP.cpp

375

It's time to refactor this function. It's better not to share all the code of lowering clauses for different LoopDirective since they does have different clauses.

Considering the following:

if (LoopDirective == llvm::omp::OMPD_do) {
  genWsLoop(...);
} else if (LoopDirective == llvm::omp::OMPD_simd) {
  genSIMDLoop(...);
} else {
  TODO
}

Or a switch case statement?

The clauses operands collection should be extracted into some functions so that they can be shared.

407

@shraiysh @kiranchandramohan Please notice that no clause is supported for SIMD in MLIR for now.

It's better not to refactor the code for wsloop before the upstream of it is done. So it seems to be better give TODOs when getting any clause in SIMD construct.

When the upstream for wsloop is done, it's better to refactor this code as I suggested above.

[arnamoy10]

Addressing reviewers comments. No test case for clauses could be added as we currently support simd without any clauses

[arnamoy10]

Addressing reviewers comments. No test case for clauses could be added as we currently support simd without any clauses

flang/lib/Lower/OpenMP.cpp

375

Not refactoring in this patch, waiting until wsloop comes, as suggested below

407

Did, thank you

[shraiysh]

LGTM. Minor changes requested. Thank you!

flang/test/Fir/convert-to-llvm-openmp-and-fir.fir

74 ↗

(On Diff #429909)

Split the testcase by adding

// -----

117 ↗

(On Diff #429909)

nit: please add a new line

flang/test/Lower/OpenMP/simd.f90

8

nit: 2-space indentation for the subroutine body.

[arnamoy10]

Rebasing and fixing minor stuff based on comments.

[kiranchandramohan]

It seems you missed the portion of the original test (Fortran -> OpenMP + FIR).

[arnamoy10]

Adding testcase, thanks @kiranchandramohan

[peixin]

LGTM

[kiranchandramohan]

LG.

Not for this patch: Maybe we should also adopt the base flang style of hard TODOs for unimplemented features/clauses.

[arnamoy10]

Rebase before land

[arnamoy10]

Fixing fortran->FIR testcase after rebasing.

flang/lib/Lower/OpenMP.cpp

createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
   }
   auto &block = op.getRegion().back();
   firOpBuilder.setInsertionPointToStart(&block);
 
   // Insert the terminator.
   if constexpr (std::is_same_v<Op, omp::WsLoopOp>) {
     mlir::ValueRange results;
     firOpBuilder.create<mlir::omp::YieldOp>(loc, results);
+  } else if constexpr (std::is_same_v<Op, omp::SimdLoopOp>) {
+    mlir::ValueRange results;
+    firOpBuilder.create<mlir::omp::YieldOp>(loc, results);
   } else {
     firOpBuilder.create<mlir::omp::TerminatorOp>(loc);
   }
 
   // Reset the insertion point to the start of the first block.
   firOpBuilder.setInsertionPointToStart(&block);
   // Handle privatization. Do not privatize if this is the outer operation.
   if (clauses && !outerCombined)
static void genOMP(Fortran::lower::AbstractConverter &converter,
   mlir::Location currentLocation = converter.getCurrentLocation();
   llvm::SmallVector<mlir::Value> lowerBound, upperBound, step, linearVars,
       linearStepVars, reductionVars;
   mlir::Value scheduleChunkClauseOperand;
   mlir::Attribute scheduleClauseOperand, collapseClauseOperand,
       noWaitClauseOperand, orderedClauseOperand, orderClauseOperand;
   const auto &wsLoopOpClauseList = std::get<Fortran::parser::OmpClauseList>(
       std::get<Fortran::parser::OmpBeginLoopDirective>(loopConstruct.t).t);
-  if (llvm::omp::OMPD_do !=
+  const auto &LoopDirective =
       std::get<Fortran::parser::OmpLoopDirective>(
           std::get<Fortran::parser::OmpBeginLoopDirective>(loopConstruct.t).t)
-          .v) {
+          .v;
+
+  if (llvm::omp::OMPD_do != LoopDirective &&
+      llvm::omp::OMPD_simd != LoopDirective) {
     TODO(converter.getCurrentLocation(), "Combined worksharing loop construct");
   }
 
   Fortran::lower::pft::Evaluation *doConstructEval =
       &eval.getFirstNestedEvaluation();
 
   Fortran::lower::pft::Evaluation *doLoop =
       &doConstructEval->getFirstNestedEvaluation();
if (bounds->step) {
     step.push_back(fir::getBase(converter.genExprValue(
         *Fortran::semantics::GetExpr(bounds->step), stmtCtx)));
   } else { // If `step` is not present, assume it as `1`.
     step.push_back(firOpBuilder.createIntegerConstant(
         currentLocation, firOpBuilder.getIntegerType(32), 1));
   }
   iv = bounds->name.thing.symbol;
 
+  // 2.9.3.1 SIMD construct
+  if (llvm::omp::OMPD_simd == LoopDirective) {
+    TypeRange resultType;
+    auto SimdLoopOp = firOpBuilder.create<mlir::omp::SimdLoopOp>(
+        currentLocation, resultType, lowerBound, upperBound, step);
+    createBodyOfOp<omp::SimdLoopOp>(SimdLoopOp, converter, currentLocation,
+                                    &wsLoopOpClauseList, iv);
+    return;
+  }
+
   // FIXME: Add support for following clauses:
   // 1. linear
   // 2. order
   // 3. collapse
   // 4. schedule (with chunk)
   auto wsLoopOp = firOpBuilder.create<mlir::omp::WsLoopOp>(
       currentLocation, lowerBound, upperBound, step, linearVars, linearStepVars,
       reductionVars, /*reductions=*/nullptr,

flang/test/Lower/OpenMP/simd.f90

+// clang-format off
+! Tests for 2.9.3.1 Simd
+
+! RUN: bbc -fopenmp -emit-fir %s -o - | tco -o - | FileCheck %s
+
+program simdloop
+        integer :: i
+
+!$OMP SIMD 
+do i=1, 9
+  print*, i
+end do
+!$OMP END SIMD 
+end
+
+
+! CHECK: %[[CALL1:.*]] = call i8* @_FortranAioBeginExternalListOutput(i32 -1, i8* getelementptr inbounds {{.*}}, !llvm.access.group ![[META1:[0-9]+]]
+! CHECK: %[[CALL2:.*]] = call i1 @_FortranAioOutputInteger32{{.*}}, !llvm.access.group ![[META1:[0-9]+]]
+! CHECK: %[[CALL3:.*]] = call i32 @_FortranAioEndIoStatement{{.*}}, !llvm.access.group ![[META1:[0-9]+]]
+! CHECK: br label %[[LOOP_HEADER:.*]], !llvm.loop ![[META2:[0-9]+]]
+
+! CHECK: ![[META1:[0-9]+]] = distinct !{}
+! CHECK: ![[META2]]  = distinct !{![[META2]], ![[META3:[0-9]+]], ![[META4:[0-9]+]]}
+! CHECK-NEXT: ![[META3]]  = !{!"llvm.loop.parallel_accesses", ![[META1]]}
+! CHECK-NEXT: ![[META4]]  = !{!"llvm.loop.vectorize.enable", i1 true}
+// clang-format on
 No newline at end of file