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Nov 30, 2023
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[flang][openacc] Support early return in acc.loop #73841

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13 changes: 10 additions & 3 deletions flang/include/flang/Lower/OpenACC.h
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Original file line number Diff line number Diff line change
Expand Up @@ -64,9 +64,10 @@ static constexpr llvm::StringRef declarePreDeallocSuffix =
static constexpr llvm::StringRef declarePostDeallocSuffix =
"_acc_declare_update_desc_post_dealloc";

void genOpenACCConstruct(AbstractConverter &,
Fortran::semantics::SemanticsContext &,
pft::Evaluation &, const parser::OpenACCConstruct &);
mlir::Value genOpenACCConstruct(AbstractConverter &,
Fortran::semantics::SemanticsContext &,
pft::Evaluation &,
const parser::OpenACCConstruct &);
void genOpenACCDeclarativeConstruct(AbstractConverter &,
Fortran::semantics::SemanticsContext &,
StatementContext &,
Expand Down Expand Up @@ -112,6 +113,12 @@ void attachDeclarePostDeallocAction(AbstractConverter &, fir::FirOpBuilder &,
void genOpenACCTerminator(fir::FirOpBuilder &, mlir::Operation *,
mlir::Location);

bool isInOpenACCLoop(fir::FirOpBuilder &);

void setInsertionPointAfterOpenACCLoopIfInside(fir::FirOpBuilder &);

void genEarlyReturnInOpenACCLoop(fir::FirOpBuilder &, mlir::Location);

} // namespace lower
} // namespace Fortran

Expand Down
23 changes: 21 additions & 2 deletions flang/lib/Lower/Bridge.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2382,11 +2382,25 @@ class FirConverter : public Fortran::lower::AbstractConverter {
void genFIR(const Fortran::parser::OpenACCConstruct &acc) {
mlir::OpBuilder::InsertPoint insertPt = builder->saveInsertionPoint();
localSymbols.pushScope();
genOpenACCConstruct(*this, bridge.getSemanticsContext(), getEval(), acc);
mlir::Value exitCond = genOpenACCConstruct(
*this, bridge.getSemanticsContext(), getEval(), acc);
for (Fortran::lower::pft::Evaluation &e : getEval().getNestedEvaluations())
genFIR(e);
localSymbols.popScope();
builder->restoreInsertionPoint(insertPt);

const Fortran::parser::OpenACCLoopConstruct *accLoop =
std::get_if<Fortran::parser::OpenACCLoopConstruct>(&acc.u);
if (accLoop && exitCond) {
Fortran::lower::pft::FunctionLikeUnit *funit =
getEval().getOwningProcedure();
assert(funit && "not inside main program, function or subroutine");
mlir::Block *continueBlock =
builder->getBlock()->splitBlock(builder->getBlock()->end());
builder->create<mlir::cf::CondBranchOp>(toLocation(), exitCond,
funit->finalBlock, continueBlock);
builder->setInsertionPointToEnd(continueBlock);
}
}

void genFIR(const Fortran::parser::OpenACCDeclarativeConstruct &accDecl) {
Expand Down Expand Up @@ -4091,10 +4105,15 @@ class FirConverter : public Fortran::lower::AbstractConverter {
// Branch to the last block of the SUBROUTINE, which has the actual return.
if (!funit->finalBlock) {
mlir::OpBuilder::InsertPoint insPt = builder->saveInsertionPoint();
Fortran::lower::setInsertionPointAfterOpenACCLoopIfInside(*builder);
funit->finalBlock = builder->createBlock(&builder->getRegion());
builder->restoreInsertionPoint(insPt);
}
builder->create<mlir::cf::BranchOp>(loc, funit->finalBlock);

if (Fortran::lower::isInOpenACCLoop(*builder))
Fortran::lower::genEarlyReturnInOpenACCLoop(*builder, loc);
else
builder->create<mlir::cf::BranchOp>(loc, funit->finalBlock);
}

void genFIR(const Fortran::parser::CycleStmt &) {
Expand Down
94 changes: 80 additions & 14 deletions flang/lib/Lower/OpenACC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,10 +25,12 @@
#include "flang/Optimizer/Builder/HLFIRTools.h"
#include "flang/Optimizer/Builder/IntrinsicCall.h"
#include "flang/Optimizer/Builder/Todo.h"
#include "flang/Parser/parse-tree-visitor.h"
#include "flang/Parser/parse-tree.h"
#include "flang/Semantics/expression.h"
#include "flang/Semantics/scope.h"
#include "flang/Semantics/tools.h"
#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
#include "llvm/Frontend/OpenACC/ACC.h.inc"

// Special value for * passed in device_type or gang clauses.
Expand Down Expand Up @@ -1381,9 +1383,10 @@ static Op createRegionOp(fir::FirOpBuilder &builder, mlir::Location loc,
Fortran::lower::pft::Evaluation &eval,
const llvm::SmallVectorImpl<mlir::Value> &operands,
const llvm::SmallVectorImpl<int32_t> &operandSegments,
bool outerCombined = false) {
llvm::ArrayRef<mlir::Type> argTy;
Op op = builder.create<Op>(loc, argTy, operands);
bool outerCombined = false,
llvm::SmallVector<mlir::Type> retTy = {},
mlir::Value yieldValue = {}) {
Op op = builder.create<Op>(loc, retTy, operands);
builder.createBlock(&op.getRegion());
mlir::Block &block = op.getRegion().back();
builder.setInsertionPointToStart(&block);
Expand All @@ -1401,7 +1404,16 @@ static Op createRegionOp(fir::FirOpBuilder &builder, mlir::Location loc,
mlir::acc::YieldOp>(
builder, eval.getNestedEvaluations());

builder.create<Terminator>(loc);
if (yieldValue) {
if constexpr (std::is_same_v<Terminator, mlir::acc::YieldOp>) {
Terminator yieldOp = builder.create<Terminator>(loc, yieldValue);
yieldValue.getDefiningOp()->moveBefore(yieldOp);
} else {
builder.create<Terminator>(loc);
}
} else {
builder.create<Terminator>(loc);
}
builder.setInsertionPointToStart(&block);
return op;
}
Expand Down Expand Up @@ -1494,7 +1506,8 @@ createLoopOp(Fortran::lower::AbstractConverter &converter,
Fortran::lower::pft::Evaluation &eval,
Fortran::semantics::SemanticsContext &semanticsContext,
Fortran::lower::StatementContext &stmtCtx,
const Fortran::parser::AccClauseList &accClauseList) {
const Fortran::parser::AccClauseList &accClauseList,
bool needEarlyReturnHandling = false) {
fir::FirOpBuilder &builder = converter.getFirOpBuilder();

mlir::Value workerNum;
Expand Down Expand Up @@ -1599,8 +1612,17 @@ createLoopOp(Fortran::lower::AbstractConverter &converter,
addOperands(operands, operandSegments, privateOperands);
addOperands(operands, operandSegments, reductionOperands);

llvm::SmallVector<mlir::Type> retTy;
mlir::Value yieldValue;
if (needEarlyReturnHandling) {
mlir::Type i1Ty = builder.getI1Type();
yieldValue = builder.createIntegerConstant(currentLocation, i1Ty, 0);
retTy.push_back(i1Ty);
}

auto loopOp = createRegionOp<mlir::acc::LoopOp, mlir::acc::YieldOp>(
builder, currentLocation, eval, operands, operandSegments);
builder, currentLocation, eval, operands, operandSegments,
/*outerCombined=*/false, retTy, yieldValue);

if (hasGang)
loopOp.setHasGangAttr(builder.getUnitAttr());
Expand Down Expand Up @@ -1647,26 +1669,48 @@ createLoopOp(Fortran::lower::AbstractConverter &converter,
return loopOp;
}

static void genACC(Fortran::lower::AbstractConverter &converter,
Fortran::semantics::SemanticsContext &semanticsContext,
Fortran::lower::pft::Evaluation &eval,
const Fortran::parser::OpenACCLoopConstruct &loopConstruct) {
static bool hasEarlyReturn(Fortran::lower::pft::Evaluation &eval) {
bool hasReturnStmt = false;
for (auto &e : eval.getNestedEvaluations()) {
e.visit(Fortran::common::visitors{
[&](const Fortran::parser::ReturnStmt &) { hasReturnStmt = true; },
[&](const auto &s) {},
});
if (e.hasNestedEvaluations())
hasReturnStmt = hasEarlyReturn(e);
}
return hasReturnStmt;
}

static mlir::Value
genACC(Fortran::lower::AbstractConverter &converter,
Fortran::semantics::SemanticsContext &semanticsContext,
Fortran::lower::pft::Evaluation &eval,
const Fortran::parser::OpenACCLoopConstruct &loopConstruct) {

const auto &beginLoopDirective =
std::get<Fortran::parser::AccBeginLoopDirective>(loopConstruct.t);
const auto &loopDirective =
std::get<Fortran::parser::AccLoopDirective>(beginLoopDirective.t);

bool needEarlyExitHandling = false;
if (eval.lowerAsUnstructured())
needEarlyExitHandling = hasEarlyReturn(eval);

mlir::Location currentLocation =
converter.genLocation(beginLoopDirective.source);
Fortran::lower::StatementContext stmtCtx;

if (loopDirective.v == llvm::acc::ACCD_loop) {
const auto &accClauseList =
std::get<Fortran::parser::AccClauseList>(beginLoopDirective.t);
createLoopOp(converter, currentLocation, eval, semanticsContext, stmtCtx,
accClauseList);
auto loopOp =
createLoopOp(converter, currentLocation, eval, semanticsContext,
stmtCtx, accClauseList, needEarlyExitHandling);
if (needEarlyExitHandling)
return loopOp.getResult(0);
}
return mlir::Value{};
}

template <typename Op, typename Clause>
Expand Down Expand Up @@ -3431,12 +3475,13 @@ genACC(Fortran::lower::AbstractConverter &converter,
builder.restoreInsertionPoint(crtPos);
}

void Fortran::lower::genOpenACCConstruct(
mlir::Value Fortran::lower::genOpenACCConstruct(
Fortran::lower::AbstractConverter &converter,
Fortran::semantics::SemanticsContext &semanticsContext,
Fortran::lower::pft::Evaluation &eval,
const Fortran::parser::OpenACCConstruct &accConstruct) {

mlir::Value exitCond;
std::visit(
common::visitors{
[&](const Fortran::parser::OpenACCBlockConstruct &blockConstruct) {
Expand All @@ -3447,7 +3492,7 @@ void Fortran::lower::genOpenACCConstruct(
genACC(converter, semanticsContext, eval, combinedConstruct);
},
[&](const Fortran::parser::OpenACCLoopConstruct &loopConstruct) {
genACC(converter, semanticsContext, eval, loopConstruct);
exitCond = genACC(converter, semanticsContext, eval, loopConstruct);
},
[&](const Fortran::parser::OpenACCStandaloneConstruct
&standaloneConstruct) {
Expand All @@ -3467,6 +3512,7 @@ void Fortran::lower::genOpenACCConstruct(
},
},
accConstruct.u);
return exitCond;
}

void Fortran::lower::genOpenACCDeclarativeConstruct(
Expand Down Expand Up @@ -3560,3 +3606,23 @@ void Fortran::lower::genOpenACCTerminator(fir::FirOpBuilder &builder,
else
builder.create<mlir::acc::TerminatorOp>(loc);
}

bool Fortran::lower::isInOpenACCLoop(fir::FirOpBuilder &builder) {
if (builder.getBlock()->getParent()->getParentOfType<mlir::acc::LoopOp>())
return true;
return false;
}

void Fortran::lower::setInsertionPointAfterOpenACCLoopIfInside(
fir::FirOpBuilder &builder) {
if (auto loopOp =
builder.getBlock()->getParent()->getParentOfType<mlir::acc::LoopOp>())
builder.setInsertionPointAfter(loopOp);
}

void Fortran::lower::genEarlyReturnInOpenACCLoop(fir::FirOpBuilder &builder,
mlir::Location loc) {
mlir::Value yieldValue =
builder.createIntegerConstant(loc, builder.getI1Type(), 1);
builder.create<mlir::acc::YieldOp>(loc, yieldValue);
}
37 changes: 37 additions & 0 deletions flang/test/Lower/OpenACC/acc-loop-exit.f90
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Original file line number Diff line number Diff line change
@@ -0,0 +1,37 @@
! RUN: bbc -fopenacc -emit-hlfir %s -o - | FileCheck %s

subroutine sub1(x, a)
real :: x(200)
integer :: a

!$acc loop
do i = 100, 200
x(i) = 1.0
if (i == a) return
end do

i = 2
end

! CHECK-LABEL: func.func @_QPsub1
! CHECK: %[[A:.*]]:2 = hlfir.declare %arg1 {uniq_name = "_QFsub1Ea"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
! CHECK: %[[EXIT_COND:.*]] = acc.loop {
! CHECK: ^bb{{.*}}:
! CHECK: ^bb{{.*}}:
! CHECK: %[[LOAD_A:.*]] = fir.load %[[A]]#0 : !fir.ref<i32>
! CHECK: %[[CMP:.*]] = arith.cmpi eq, %15, %[[LOAD_A]] : i32
! CHECK: cf.cond_br %[[CMP]], ^[[EARLY_RET:.*]], ^[[NO_RET:.*]]
! CHECK: ^[[EARLY_RET]]:
! CHECK: acc.yield %true : i1
! CHECK: ^[[NO_RET]]:
! CHECK: cf.br ^bb{{.*}}
! CHECK: ^bb{{.*}}:
! CHECK: acc.yield %false : i1
! CHECK: }(i1)
! CHECK: cf.cond_br %[[EXIT_COND]], ^[[EXIT_BLOCK:.*]], ^[[CONTINUE_BLOCK:.*]]
! CHECK: ^[[CONTINUE_BLOCK]]:
! CHECK: hlfir.assign
! CHECK: cf.br ^[[EXIT_BLOCK]]
! CHECK: ^[[EXIT_BLOCK]]:
! CHECK: return
! CHECK: }