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Apr 28, 2025
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[mlir][OpenMP] Convert omp.cancel parallel to LLVMIR #137192

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[mlir][OpenMP] Convert omp.cancel parallel to LLVMIR
tblah Apr 8, 2025
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tblah Apr 25, 2025
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67 changes: 65 additions & 2 deletions mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,12 @@ static LogicalResult checkImplementationStatus(Operation &op) {
if (op.getBare())
result = todo("ompx_bare");
};
auto checkCancelDirective = [&todo](auto op, LogicalResult &result) {
omp::ClauseCancellationConstructType cancelledDirective =
op.getCancelDirective();
if (cancelledDirective != omp::ClauseCancellationConstructType::Parallel)
result = todo("cancel directive construct type not yet supported");
};
auto checkDepend = [&todo](auto op, LogicalResult &result) {
if (!op.getDependVars().empty() || op.getDependKinds())
result = todo("depend");
Expand Down Expand Up @@ -248,6 +254,7 @@ static LogicalResult checkImplementationStatus(Operation &op) {

LogicalResult result = success();
llvm::TypeSwitch<Operation &>(op)
.Case([&](omp::CancelOp op) { checkCancelDirective(op, result); })
.Case([&](omp::DistributeOp op) {
checkAllocate(op, result);
checkDistSchedule(op, result);
Expand Down Expand Up @@ -1580,6 +1587,19 @@ cleanupPrivateVars(llvm::IRBuilderBase &builder,
return success();
}

/// Returns true if the construct contains omp.cancel or omp.cancellation_point
static bool constructIsCancellable(Operation *op) {
// omp.cancel must be "closely nested" so it will be visible and not inside of
// funcion calls. This is enforced by the verifier.
return op
->walk([](Operation *child) {
if (mlir::isa<omp::CancelOp>(child))
return WalkResult::interrupt();
return WalkResult::advance();
})
.wasInterrupted();
}

static LogicalResult
convertOmpSections(Operation &opInst, llvm::IRBuilderBase &builder,
LLVM::ModuleTranslation &moduleTranslation) {
Expand Down Expand Up @@ -2524,8 +2544,7 @@ convertOmpParallel(omp::ParallelOp opInst, llvm::IRBuilderBase &builder,
auto pbKind = llvm::omp::OMP_PROC_BIND_default;
if (auto bind = opInst.getProcBindKind())
pbKind = getProcBindKind(*bind);
// TODO: Is the Parallel construct cancellable?
bool isCancellable = false;
bool isCancellable = constructIsCancellable(opInst);

llvm::OpenMPIRBuilder::InsertPointTy allocaIP =
findAllocaInsertPoint(builder, moduleTranslation);
Expand Down Expand Up @@ -2991,6 +3010,47 @@ convertOmpAtomicCapture(omp::AtomicCaptureOp atomicCaptureOp,
return success();
}

static llvm::omp::Directive convertCancellationConstructType(
omp::ClauseCancellationConstructType directive) {
switch (directive) {
case omp::ClauseCancellationConstructType::Loop:
return llvm::omp::Directive::OMPD_for;
case omp::ClauseCancellationConstructType::Parallel:
return llvm::omp::Directive::OMPD_parallel;
case omp::ClauseCancellationConstructType::Sections:
return llvm::omp::Directive::OMPD_sections;
case omp::ClauseCancellationConstructType::Taskgroup:
return llvm::omp::Directive::OMPD_taskgroup;
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Should this be a TODO? I noticed that cancel on taskgroup is a TODO, rest all are PR stack.

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The TODO is generated by checkImplementationStatus.

}
}

static LogicalResult
convertOmpCancel(omp::CancelOp op, llvm::IRBuilderBase &builder,
LLVM::ModuleTranslation &moduleTranslation) {
llvm::OpenMPIRBuilder::LocationDescription ompLoc(builder);
llvm::OpenMPIRBuilder *ompBuilder = moduleTranslation.getOpenMPBuilder();

if (failed(checkImplementationStatus(*op.getOperation())))
return failure();

llvm::Value *ifCond = nullptr;
if (Value ifVar = op.getIfExpr())
ifCond = moduleTranslation.lookupValue(ifVar);

llvm::omp::Directive cancelledDirective =
convertCancellationConstructType(op.getCancelDirective());

llvm::OpenMPIRBuilder::InsertPointOrErrorTy afterIP =
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ifCond is a nullptr and then is assigned through a lookupValue. Do we need an assert before using it in createCancel?

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nullptr is how the absence of an if clause is represented and this his handled in openmp ir builder

llvm-project/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

Line 1076 in 6ae4030

if (IfCondition)

ompBuilder->createCancel(ompLoc, ifCond, cancelledDirective);

if (failed(handleError(afterIP, *op.getOperation())))
return failure();

builder.restoreIP(afterIP.get());

return success();
}

/// Converts an OpenMP Threadprivate operation into LLVM IR using
/// OpenMPIRBuilder.
static LogicalResult
Expand Down Expand Up @@ -5421,6 +5481,9 @@ convertHostOrTargetOperation(Operation *op, llvm::IRBuilderBase &builder,
.Case([&](omp::AtomicCaptureOp op) {
return convertOmpAtomicCapture(op, builder, moduleTranslation);
})
.Case([&](omp::CancelOp op) {
return convertOmpCancel(op, builder, moduleTranslation);
})
.Case([&](omp::SectionsOp) {
return convertOmpSections(*op, builder, moduleTranslation);
})
Expand Down
82 changes: 82 additions & 0 deletions mlir/test/Target/LLVMIR/openmp-cancel.mlir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,82 @@
// RUN: mlir-translate --mlir-to-llvmir %s | FileCheck %s

llvm.func @cancel_parallel() {
omp.parallel {
omp.cancel cancellation_construct_type(parallel)
omp.terminator
}
llvm.return
}
// CHECK-LABEL: define internal void @cancel_parallel..omp_par
// CHECK: omp.par.entry:
// CHECK: %[[VAL_5:.*]] = alloca i32, align 4
// CHECK: %[[VAL_6:.*]] = load i32, ptr %[[VAL_7:.*]], align 4
// CHECK: store i32 %[[VAL_6]], ptr %[[VAL_5]], align 4
// CHECK: %[[VAL_8:.*]] = load i32, ptr %[[VAL_5]], align 4
// CHECK: br label %[[VAL_9:.*]]
// CHECK: omp.region.after_alloca: ; preds = %[[VAL_10:.*]]
// CHECK: br label %[[VAL_11:.*]]
// CHECK: omp.par.region: ; preds = %[[VAL_9]]
// CHECK: br label %[[VAL_12:.*]]
// CHECK: omp.par.region1: ; preds = %[[VAL_11]]
// CHECK: %[[VAL_13:.*]] = call i32 @__kmpc_global_thread_num(ptr @1)
// CHECK: %[[VAL_14:.*]] = call i32 @__kmpc_cancel(ptr @1, i32 %[[VAL_13]], i32 1)
// CHECK: %[[VAL_15:.*]] = icmp eq i32 %[[VAL_14]], 0
// CHECK: br i1 %[[VAL_15]], label %[[VAL_16:.*]], label %[[VAL_17:.*]]
// CHECK: omp.par.region1.cncl: ; preds = %[[VAL_12]]
// CHECK: %[[VAL_18:.*]] = call i32 @__kmpc_global_thread_num(ptr @1)
// CHECK: %[[VAL_19:.*]] = call i32 @__kmpc_cancel_barrier(ptr @2, i32 %[[VAL_18]])
// CHECK: br label %[[VAL_20:.*]]
// CHECK: omp.par.region1.split: ; preds = %[[VAL_12]]
// CHECK: br label %[[VAL_21:.*]]
// CHECK: omp.region.cont: ; preds = %[[VAL_16]]
// CHECK: br label %[[VAL_22:.*]]
// CHECK: omp.par.pre_finalize: ; preds = %[[VAL_21]]
// CHECK: br label %[[VAL_20]]
// CHECK: omp.par.exit.exitStub: ; preds = %[[VAL_22]], %[[VAL_17]]
// CHECK: ret void

llvm.func @cancel_parallel_if(%arg0 : i1) {
omp.parallel {
omp.cancel cancellation_construct_type(parallel) if(%arg0)
omp.terminator
}
llvm.return
}
// CHECK-LABEL: define internal void @cancel_parallel_if..omp_par
// CHECK: omp.par.entry:
// CHECK: %[[VAL_9:.*]] = getelementptr { ptr }, ptr %[[VAL_10:.*]], i32 0, i32 0
// CHECK: %[[VAL_11:.*]] = load ptr, ptr %[[VAL_9]], align 8
// CHECK: %[[VAL_12:.*]] = alloca i32, align 4
// CHECK: %[[VAL_13:.*]] = load i32, ptr %[[VAL_14:.*]], align 4
// CHECK: store i32 %[[VAL_13]], ptr %[[VAL_12]], align 4
// CHECK: %[[VAL_15:.*]] = load i32, ptr %[[VAL_12]], align 4
// CHECK: %[[VAL_16:.*]] = load i1, ptr %[[VAL_11]], align 1
// CHECK: br label %[[VAL_17:.*]]
// CHECK: omp.region.after_alloca: ; preds = %[[VAL_18:.*]]
// CHECK: br label %[[VAL_19:.*]]
// CHECK: omp.par.region: ; preds = %[[VAL_17]]
// CHECK: br label %[[VAL_20:.*]]
// CHECK: omp.par.region1: ; preds = %[[VAL_19]]
// CHECK: br i1 %[[VAL_16]], label %[[VAL_21:.*]], label %[[VAL_22:.*]]
// CHECK: 3: ; preds = %[[VAL_20]]
// CHECK: br label %[[VAL_23:.*]]
// CHECK: 4: ; preds = %[[VAL_22]], %[[VAL_24:.*]]
// CHECK: br label %[[VAL_25:.*]]
// CHECK: omp.region.cont: ; preds = %[[VAL_23]]
// CHECK: br label %[[VAL_26:.*]]
// CHECK: omp.par.pre_finalize: ; preds = %[[VAL_25]]
// CHECK: br label %[[VAL_27:.*]]
// CHECK: 5: ; preds = %[[VAL_20]]
// CHECK: %[[VAL_28:.*]] = call i32 @__kmpc_global_thread_num(ptr @1)
// CHECK: %[[VAL_29:.*]] = call i32 @__kmpc_cancel(ptr @1, i32 %[[VAL_28]], i32 1)
// CHECK: %[[VAL_30:.*]] = icmp eq i32 %[[VAL_29]], 0
// CHECK: br i1 %[[VAL_30]], label %[[VAL_24]], label %[[VAL_31:.*]]
// CHECK: .cncl: ; preds = %[[VAL_21]]
// CHECK: %[[VAL_32:.*]] = call i32 @__kmpc_global_thread_num(ptr @1)
// CHECK: %[[VAL_33:.*]] = call i32 @__kmpc_cancel_barrier(ptr @2, i32 %[[VAL_32]])
// CHECK: br label %[[VAL_27]]
// CHECK: .split: ; preds = %[[VAL_21]]
// CHECK: br label %[[VAL_23]]
// CHECK: omp.par.exit.exitStub: ; preds = %[[VAL_31]], %[[VAL_26]]
// CHECK: ret void
48 changes: 42 additions & 6 deletions mlir/test/Target/LLVMIR/openmp-todo.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -26,12 +26,48 @@ llvm.func @atomic_hint(%v : !llvm.ptr, %x : !llvm.ptr, %expr : i32) {

// -----

llvm.func @cancel() {
// expected-error@below {{LLVM Translation failed for operation: omp.parallel}}
omp.parallel {
// expected-error@below {{not yet implemented: omp.cancel}}
// expected-error@below {{LLVM Translation failed for operation: omp.cancel}}
omp.cancel cancellation_construct_type(parallel)
llvm.func @cancel_wsloop(%lb : i32, %ub : i32, %step: i32) {
// expected-error@below {{LLVM Translation failed for operation: omp.wsloop}}
omp.wsloop {
// expected-error@below {{LLVM Translation failed for operation: omp.loop_nest}}
omp.loop_nest (%iv) : i32 = (%lb) to (%ub) step (%step) {
// expected-error@below {{not yet implemented: Unhandled clause cancel directive construct type not yet supported in omp.cancel operation}}
// expected-error@below {{LLVM Translation failed for operation: omp.cancel}}
omp.cancel cancellation_construct_type(loop)
omp.yield
}
}
llvm.return
}

// -----

llvm.func @cancel_sections() {
// expected-error@below {{LLVM Translation failed for operation: omp.sections}}
omp.sections {
omp.section {
// expected-error@below {{not yet implemented: Unhandled clause cancel directive construct type not yet supported in omp.cancel operation}}
// expected-error@below {{LLVM Translation failed for operation: omp.cancel}}
omp.cancel cancellation_construct_type(sections)
omp.terminator
}
omp.terminator
}
llvm.return
}

// -----

llvm.func @cancel_taskgroup() {
// expected-error@below {{LLVM Translation failed for operation: omp.taskgroup}}
omp.taskgroup {
// expected-error@below {{LLVM Translation failed for operation: omp.task}}
omp.task {
// expected-error@below {{not yet implemented: Unhandled clause cancel directive construct type not yet supported in omp.cancel operation}}
// expected-error@below {{LLVM Translation failed for operation: omp.cancel}}
omp.cancel cancellation_construct_type(taskgroup)
omp.terminator
}
omp.terminator
}
llvm.return
Expand Down
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