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[Flang][OpenMP] Fixes for unstructured OpenMP code
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Since the FIR operations are mostly structured, it is only the functions
that could contain multiple blocks inside an operation. This changes
with OpenMP since OpenMP regions can contain multiple blocks. For
unstructured code, the blocks are created in advance and belong to the
top-level function. This caused code in OpenMP region to be placed under
the function level.

In this fix, if the OpenMP region is unstructured then new blocks are
created inside it.

Note1: This is part of upstreaming from the fir-dev branch of
https://github.com/flang-compiler/f18-llvm-project. The code in this patch is a
subset of the changes in flang-compiler#1178.

Reviewed By: vdonaldson

Differential Revision: https://reviews.llvm.org/D126293

Co-authored-by: Val Donaldson <[email protected]>
Co-authored-by: Eric Schweitz <[email protected]>
Co-authored-by: Valentin Clement <[email protected]>
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@kiranchandramohan @vdonaldson
@schweitzpgi @clementval
4 people committed May 24, 2022
1 parent 0bf3c38 commit 29f167a
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Showing 2 changed files with 159 additions and 17 deletions.
63 changes: 46 additions & 17 deletions flang/lib/Lower/OpenMP.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -138,11 +138,35 @@ static mlir::Type getLoopVarType(Fortran::lower::AbstractConverter &converter,
return converter.getFirOpBuilder().getIntegerType(loopVarTypeSize);
}

/// Create empty blocks for the current region.
/// These blocks replace blocks parented to an enclosing region.
void createEmptyRegionBlocks(
fir::FirOpBuilder &firOpBuilder,
std::list<Fortran::lower::pft::Evaluation> &evaluationList) {
auto *region = &firOpBuilder.getRegion();
for (auto &eval : evaluationList) {
if (eval.block) {
if (eval.block->empty()) {
eval.block->erase();
eval.block = firOpBuilder.createBlock(region);
} else {
[[maybe_unused]] auto &terminatorOp = eval.block->back();
assert((mlir::isa<mlir::omp::TerminatorOp>(terminatorOp) ||
mlir::isa<mlir::omp::YieldOp>(terminatorOp)) &&
"expected terminator op");
}
}
if (eval.hasNestedEvaluations())
createEmptyRegionBlocks(firOpBuilder, eval.getNestedEvaluations());
}
}

/// Create the body (block) for an OpenMP Operation.
///
/// \param [in] op - the operation the body belongs to.
/// \param [inout] converter - converter to use for the clauses.
/// \param [in] loc - location in source code.
/// \param [in] eval - current PFT node/evaluation.
/// \oaran [in] clauses - list of clauses to process.
/// \param [in] args - block arguments (induction variable[s]) for the
//// region.
Expand All @@ -151,14 +175,14 @@ static mlir::Type getLoopVarType(Fortran::lower::AbstractConverter &converter,
template <typename Op>
static void
createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
mlir::Location &loc,
mlir::Location &loc, Fortran::lower::pft::Evaluation &eval,
const Fortran::parser::OmpClauseList *clauses = nullptr,
const SmallVector<const Fortran::semantics::Symbol *> &args = {},
bool outerCombined = false) {
fir::FirOpBuilder &firOpBuilder = converter.getFirOpBuilder();
// If arguments for the region are provided then create the block with those
// arguments. Also update the symbol's address with the mlir argument values.
// e.g. For loops the arguments are the induction variable. And all further
auto &firOpBuilder = converter.getFirOpBuilder();
// If an argument for the region is provided then create the block with that
// argument. Also update the symbol's address with the mlir argument value.
// e.g. For loops the argument is the induction variable. And all further
// uses of the induction variable should use this mlir value.
if (args.size()) {
std::size_t loopVarTypeSize = 0;
Expand All @@ -184,7 +208,10 @@ createBodyOfOp(Op &op, Fortran::lower::AbstractConverter &converter,
auto &block = op.getRegion().back();
firOpBuilder.setInsertionPointToStart(&block);

// Insert the terminator.
if (eval.lowerAsUnstructured())
createEmptyRegionBlocks(firOpBuilder, eval.getNestedEvaluations());

// Ensure the block is well-formed by inserting terminators.
if constexpr (std::is_same_v<Op, omp::WsLoopOp>) {
mlir::ValueRange results;
firOpBuilder.create<mlir::omp::YieldOp>(loc, results);
Expand Down Expand Up @@ -369,7 +396,7 @@ createCombinedParallelOp(Fortran::lower::AbstractConverter &converter,
allocateOperands, allocatorOperands, /*reduction_vars=*/ValueRange(),
/*reductions=*/nullptr, procBindKindAttr);

createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation,
createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation, eval,
&opClauseList, /*iv=*/{},
/*isCombined=*/true);
}
Expand Down Expand Up @@ -461,26 +488,27 @@ genOMP(Fortran::lower::AbstractConverter &converter,
allocateOperands, allocatorOperands, /*reduction_vars=*/ValueRange(),
/*reductions=*/nullptr, procBindKindAttr);
createBodyOfOp<omp::ParallelOp>(parallelOp, converter, currentLocation,
&opClauseList);
eval, &opClauseList);
} else if (blockDirective.v == llvm::omp::OMPD_master) {
auto masterOp =
firOpBuilder.create<mlir::omp::MasterOp>(currentLocation, argTy);
createBodyOfOp<omp::MasterOp>(masterOp, converter, currentLocation);
createBodyOfOp<omp::MasterOp>(masterOp, converter, currentLocation, eval);
} else if (blockDirective.v == llvm::omp::OMPD_single) {
auto singleOp = firOpBuilder.create<mlir::omp::SingleOp>(
currentLocation, allocateOperands, allocatorOperands, nowaitAttr);
createBodyOfOp<omp::SingleOp>(singleOp, converter, currentLocation);
createBodyOfOp<omp::SingleOp>(singleOp, converter, currentLocation, eval);
} else if (blockDirective.v == llvm::omp::OMPD_ordered) {
auto orderedOp = firOpBuilder.create<mlir::omp::OrderedRegionOp>(
currentLocation, /*simd=*/nullptr);
createBodyOfOp<omp::OrderedRegionOp>(orderedOp, converter, currentLocation);
createBodyOfOp<omp::OrderedRegionOp>(orderedOp, converter, currentLocation,
eval);
} else if (blockDirective.v == llvm::omp::OMPD_task) {
auto taskOp = firOpBuilder.create<mlir::omp::TaskOp>(
currentLocation, ifClauseOperand, finalClauseOperand, untiedAttr,
mergeableAttr, /*in_reduction_vars=*/ValueRange(),
/*in_reductions=*/nullptr, priorityClauseOperand, allocateOperands,
allocatorOperands);
createBodyOfOp(taskOp, converter, currentLocation, &opClauseList);
createBodyOfOp(taskOp, converter, currentLocation, eval, &opClauseList);
} else {
TODO(converter.getCurrentLocation(), "Unhandled block directive");
}
Expand Down Expand Up @@ -644,7 +672,7 @@ static void genOMP(Fortran::lower::AbstractConverter &converter,
wsLoopOp.nowaitAttr(firOpBuilder.getUnitAttr());
}

createBodyOfOp<omp::WsLoopOp>(wsLoopOp, converter, currentLocation,
createBodyOfOp<omp::WsLoopOp>(wsLoopOp, converter, currentLocation, eval,
&wsLoopOpClauseList, iv);
}

Expand Down Expand Up @@ -688,7 +716,7 @@ genOMP(Fortran::lower::AbstractConverter &converter,
firOpBuilder.getContext(), global.sym_name()));
}
}();
createBodyOfOp<omp::CriticalOp>(criticalOp, converter, currentLocation);
createBodyOfOp<omp::CriticalOp>(criticalOp, converter, currentLocation, eval);
}

static void
Expand All @@ -700,7 +728,7 @@ genOMP(Fortran::lower::AbstractConverter &converter,
auto currentLocation = converter.getCurrentLocation();
mlir::omp::SectionOp sectionOp =
firOpBuilder.create<mlir::omp::SectionOp>(currentLocation);
createBodyOfOp<omp::SectionOp>(sectionOp, converter, currentLocation);
createBodyOfOp<omp::SectionOp>(sectionOp, converter, currentLocation, eval);
}

// TODO: Add support for reduction
Expand Down Expand Up @@ -757,14 +785,15 @@ genOMP(Fortran::lower::AbstractConverter &converter,
currentLocation, /*reduction_vars*/ ValueRange(),
/*reductions=*/nullptr, allocateOperands, allocatorOperands,
/*nowait=*/nullptr);
createBodyOfOp(sectionsOp, converter, currentLocation);
createBodyOfOp(sectionsOp, converter, currentLocation, eval);

// Sections Construct
} else if (dir == llvm::omp::Directive::OMPD_sections) {
auto sectionsOp = firOpBuilder.create<mlir::omp::SectionsOp>(
currentLocation, reductionVars, /*reductions = */ nullptr,
allocateOperands, allocatorOperands, noWaitClauseOperand);
createBodyOfOp<omp::SectionsOp>(sectionsOp, converter, currentLocation);
createBodyOfOp<omp::SectionsOp>(sectionsOp, converter, currentLocation,
eval);
}
}

Expand Down
113 changes: 113 additions & 0 deletions flang/test/Lower/OpenMP/omp-unstructured.f90
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,113 @@
! Test unstructured code adjacent to and inside OpenMP constructs.

! RUN: bbc %s -fopenmp -o "-" | FileCheck %s

! CHECK-LABEL: func @_QPss1{{.*}} {
! CHECK: br ^bb1
! CHECK: ^bb1: // 2 preds: ^bb0, ^bb3
! CHECK: cond_br %{{[0-9]*}}, ^bb2, ^bb4
! CHECK: ^bb2: // pred: ^bb1
! CHECK: cond_br %{{[0-9]*}}, ^bb4, ^bb3
! CHECK: ^bb3: // pred: ^bb2
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: br ^bb1
! CHECK: ^bb4: // 2 preds: ^bb1, ^bb2
! CHECK: omp.master {
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: omp.terminator
! CHECK: }
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: }
subroutine ss1(n) ! unstructured code followed by a structured OpenMP construct
do i = 1, 3
if (i .eq. n) exit
print*, 'ss1-A', i
enddo
!$omp master
print*, 'ss1-B', i
!$omp end master
print*
end

! CHECK-LABEL: func @_QPss2{{.*}} {
! CHECK: omp.master {
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: br ^bb1
! CHECK: ^bb1: // 2 preds: ^bb0, ^bb3
! CHECK: cond_br %{{[0-9]*}}, ^bb2, ^bb4
! CHECK: ^bb2: // pred: ^bb1
! CHECK: cond_br %{{[0-9]*}}, ^bb4, ^bb3
! CHECK: ^bb3: // pred: ^bb2
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: br ^bb1
! CHECK: ^bb4: // 2 preds: ^bb1, ^bb2
! CHECK: omp.terminator
! CHECK: }
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: }
subroutine ss2(n) ! unstructured OpenMP construct; loop exit inside construct
!$omp master
print*, 'ss2-A', n
do i = 1, 3
if (i .eq. n) exit
print*, 'ss2-B', i
enddo
!$omp end master
print*, 'ss2-C', i
print*
end

! CHECK-LABEL: func @_QPss3{{.*}} {
! CHECK: omp.parallel {
! CHECK: br ^bb1
! CHECK: ^bb1: // 2 preds: ^bb0, ^bb2
! CHECK: cond_br %{{[0-9]*}}, ^bb2, ^bb3
! CHECK: ^bb2: // pred: ^bb1
! CHECK: omp.wsloop {{.*}} {
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: omp.yield
! CHECK: }
! CHECK: omp.wsloop {{.*}} {
! CHECK: br ^bb1
! CHECK: ^bb1: // 2 preds: ^bb0, ^bb3
! CHECK: cond_br %{{[0-9]*}}, ^bb2, ^bb4
! CHECK: ^bb2: // pred: ^bb1
! CHECK: cond_br %{{[0-9]*}}, ^bb4, ^bb3
! CHECK: ^bb3: // pred: ^bb2
! CHECK: @_FortranAioBeginExternalListOutput
! CHECK: br ^bb1
! CHECK: ^bb4: // 2 preds: ^bb1, ^bb2
! CHECK: omp.yield
! CHECK: }
! CHECK: br ^bb1
! CHECK: ^bb3: // pred: ^bb1
! CHECK: omp.terminator
! CHECK: }
! CHECK: }
subroutine ss3(n) ! nested unstructured OpenMP constructs
!$omp parallel
do i = 1, 3
!$omp do
do k = 1, 3
print*, 'ss3-A', k
enddo
!$omp end do
!$omp do
do j = 1, 3
do k = 1, 3
if (k .eq. n) exit
print*, 'ss3-B', k
enddo
enddo
!$omp end do
enddo
!$omp end parallel
end

! CHECK-LABEL: func @_QQmain
program p
call ss1(2)
call ss2(2)
call ss3(2)
end

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