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[flang][OpenMP] Process omp.atomic.update while translating scopes for target device #132165

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Merged
dpalermo merged 2 commits into from
Mar 20, 2025
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[flang][OpenMP] Process omp.atomic.update while translating scopes for target device #132165

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[flang][OpenMP] Process `omp.atomic.update` while translating scopes …
ergawy Mar 20, 2025
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ergawy Mar 20, 2025
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17 changes: 16 additions & 1 deletion mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5323,6 +5323,20 @@ convertTargetOpsInNest(Operation *op, llvm::IRBuilderBase &builder,
if (auto blockArgsIface =
dyn_cast<omp::BlockArgOpenMPOpInterface>(oper))
forwardArgs(moduleTranslation, blockArgsIface);
else {
// Here we map entry block arguments of
// non-BlockArgOpenMPOpInterface ops if they can be encountered
// inside of a function and they define any of these arguments.
if (isa<mlir::omp::AtomicUpdateOp>(oper))
for (auto [operand, arg] :
llvm::zip_equal(oper->getOperands(),
oper->getRegion(0).getArguments())) {
moduleTranslation.mapValue(
arg, builder.CreateLoad(
moduleTranslation.convertType(arg.getType()),
moduleTranslation.lookupValue(operand)));
}
}

if (auto loopNest = dyn_cast<omp::LoopNestOp>(oper)) {
assert(builder.GetInsertBlock() &&
Expand All @@ -5340,9 +5354,10 @@ convertTargetOpsInNest(Operation *op, llvm::IRBuilderBase &builder,
// translation of the OpenMP construct being converted (e.g. no
// OpenMP runtime calls will be generated). We just need this to
// prepare the kernel invocation args.
SmallVector<llvm::PHINode *> phis;
auto result = convertOmpOpRegions(
region, oper->getName().getStringRef().str() + ".fake.region",
builder, moduleTranslation);
builder, moduleTranslation, &phis);
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@skatrak skatrak Mar 20, 2025

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I see phis isn't used. Does passing the vector on its own cause a behavior change?

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@ergawy ergawy Mar 20, 2025

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Yes, since omp.atomic.update yields values (which are not used in this context), convertOmpOpRegions asserts unless we pass a vector to collect the phis.

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@skatrak skatrak Mar 20, 2025

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Ah I see, and I guess not using these PHI nodes later doesn't cause issues. Thanks for the explanation!

if (failed(handleError(result, *oper)))
return WalkResult::interrupt();

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21 changes: 21 additions & 0 deletions mlir/test/Target/LLVMIR/openmp-target-nesting-in-host-ops.mlir
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Expand Up @@ -97,6 +97,20 @@ module attributes {llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_gpu = true,
llvm.return
}

llvm.func @test_target_and_atomic_update(%x: !llvm.ptr, %expr : i32) {
omp.target {
omp.terminator
}

omp.atomic.update %x : !llvm.ptr {
^bb0(%xval: i32):
%newval = llvm.add %xval, %expr : i32
omp.yield(%newval : i32)
}

llvm.return
}

// CHECK-LABEL: define void @test_nested_target_in_parallel_with_private({{.*}}) {
// CHECK: br label %omp.parallel.fake.region
// CHECK: omp.parallel.fake.region:
Expand Down Expand Up @@ -132,4 +146,11 @@ module attributes {llvm.target_triple = "amdgcn-amd-amdhsa", omp.is_gpu = true,
// CHECK: call void @__kmpc_target_deinit()
// CHECK: ret void
// CHECK: }

// CHECK-LABEL: define {{.*}} amdgpu_kernel void @__omp_offloading_{{.*}}_test_target_and_atomic_update_{{.*}} {
// CHECK: call i32 @__kmpc_target_init
// CHECK: user_code.entry:
// CHECK: call void @__kmpc_target_deinit()
// CHECK: ret void
// CHECK: }
}