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[MLIR][OpenMP] Extend omp.private materialization support: firstprivate #83761

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Original file line number Diff line number Diff line change
Expand Up @@ -1190,17 +1190,38 @@ convertOmpParallel(omp::ParallelOp opInst, llvm::IRBuilderBase &builder,
}();

if (privVar) {
Region &allocRegion = privatizerClone.getAllocRegion();

// If this is a `firstprivate` clause, prepare the `omp.private` op by:
if (privatizerClone.getDataSharingType() ==
omp::DataSharingClauseType::FirstPrivate) {
privatizerClone.emitOpError(
"TODO: delayed privatization is not "
"supported for `firstprivate` clauses yet.");
bodyGenStatus = failure();
return codeGenIP;
auto oldAllocBackBlock = std::prev(allocRegion.end());
omp::YieldOp oldAllocYieldOp =
llvm::cast<omp::YieldOp>(oldAllocBackBlock->getTerminator());

Region &copyRegion = privatizerClone.getCopyRegion();

mlir::IRRewriter copyCloneBuilder(&moduleTranslation.getContext());
// 1. Cloning the `copy` region to the end of the `alloc` region.
copyCloneBuilder.cloneRegionBefore(copyRegion, allocRegion,
allocRegion.end());

auto newCopyRegionFrontBlock = std::next(oldAllocBackBlock);
// 2. Merging the last `alloc` block with the first block in the `copy`
// region clone.
// 3. Re-mapping the first argument of the `copy` region to be the
// argument of the `alloc` region and the second argument of the `copy`
// region to be the yielded value of the `alloc` region (this is the
// private clone of the privatized value).
copyCloneBuilder.mergeBlocks(
&*newCopyRegionFrontBlock, &*oldAllocBackBlock,
{allocRegion.getArgument(0), oldAllocYieldOp.getOperand(0)});

// 4. The old terminator of the `alloc` region is not needed anymore, so
// delete it.
oldAllocYieldOp.erase();
}

Region &allocRegion = privatizerClone.getAllocRegion();

// Replace the privatizer block argument with mlir value being privatized.
// This way, the body of the privatizer will be changed from using the
// region/block argument to the value being privatized.
Expand Down
116 changes: 116 additions & 0 deletions mlir/test/Target/LLVMIR/openmp-firstprivate.mlir
Original file line number Diff line number Diff line change
@@ -0,0 +1,116 @@
// Test code-gen for `omp.parallel` ops with delayed privatizers (i.e. using
// `omp.private` ops).

// RUN: mlir-translate -mlir-to-llvmir -split-input-file %s | FileCheck %s

llvm.func @parallel_op_firstprivate(%arg0: !llvm.ptr) {
omp.parallel private(@x.privatizer %arg0 -> %arg2 : !llvm.ptr) {
%0 = llvm.load %arg2 : !llvm.ptr -> f32
omp.terminator
}
llvm.return
}

omp.private {type = firstprivate} @x.privatizer : !llvm.ptr alloc {
^bb0(%arg0: !llvm.ptr):
%c1 = llvm.mlir.constant(1 : i32) : i32
%0 = llvm.alloca %c1 x f32 : (i32) -> !llvm.ptr
omp.yield(%0 : !llvm.ptr)
} copy {
^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr):
%0 = llvm.load %arg0 : !llvm.ptr -> f32
llvm.store %0, %arg1 : f32, !llvm.ptr
omp.yield(%arg1 : !llvm.ptr)
}

// CHECK-LABEL: @parallel_op_firstprivate
// CHECK-SAME: (ptr %[[ORIG:.*]]) {
// CHECK: %[[OMP_PAR_ARG:.*]] = alloca { ptr }, align 8
// CHECK: %[[ORIG_GEP:.*]] = getelementptr { ptr }, ptr %[[OMP_PAR_ARG]], i32 0, i32 0
// CHECK: store ptr %[[ORIG]], ptr %[[ORIG_GEP]], align 8
// CHECK: call void (ptr, i32, ptr, ...) @__kmpc_fork_call(ptr @1, i32 1, ptr @parallel_op_firstprivate..omp_par, ptr %[[OMP_PAR_ARG]])
// CHECK: }

// CHECK-LABEL: void @parallel_op_firstprivate..omp_par
// CHECK-SAME: (ptr noalias %{{.*}}, ptr noalias %{{.*}}, ptr %[[ARG:.*]])
// CHECK: %[[ORIG_PTR_PTR:.*]] = getelementptr { ptr }, ptr %[[ARG]], i32 0, i32 0
// CHECK: %[[ORIG_PTR:.*]] = load ptr, ptr %[[ORIG_PTR_PTR]], align 8

// Check that the privatizer alloc region was inlined properly.
// CHECK: %[[PRIV_ALLOC:.*]] = alloca float, align 4

// Check that the privatizer copy region was inlined properly.

// CHECK: %[[ORIG_VAL:.*]] = load float, ptr %[[ORIG_PTR]], align 4
// CHECK: store float %[[ORIG_VAL]], ptr %[[PRIV_ALLOC]], align 4
// CHECK-NEXT: br

// Check that the privatized value is used (rather than the original one).
// CHECK: load float, ptr %[[PRIV_ALLOC]], align 4
// CHECK: }

// -----

llvm.func @parallel_op_firstprivate_multi_block(%arg0: !llvm.ptr) {
omp.parallel private(@multi_block.privatizer %arg0 -> %arg2 : !llvm.ptr) {
%0 = llvm.load %arg2 : !llvm.ptr -> f32
omp.terminator
}
llvm.return
}

// CHECK-LABEL: define internal void @parallel_op_firstprivate_multi_block..omp_par
// CHECK: omp.par.entry:
// CHECK: %[[ORIG_PTR_PTR:.*]] = getelementptr { ptr }, ptr %{{.*}}, i32 0, i32 0
// CHECK: %[[ORIG_PTR:.*]] = load ptr, ptr %[[ORIG_PTR_PTR]], align 8
// CHECK: br label %[[PRIV_BB1:.*]]

// CHECK: [[PRIV_BB1]]:
// The 1st `alloc` block directly branches to the 2nd `alloc` block since the
// only insruction is `llvm.mlir.constant` which gets translated to compile-time
// constant in LLVM IR.
// CHECK-NEXT: br label %[[PRIV_BB2:.*]]

// CHECK: [[PRIV_BB2]]:
// CHECK-NEXT: %[[C1:.*]] = phi i32 [ 1, %[[PRIV_BB1]] ]
// CHECK-NEXT: %[[PRIV_ALLOC:.*]] = alloca float, i32 %[[C1]], align 4
// The entry block of the `copy` region is merged into the exit block of the
// `alloc` region. So check for that.
// CHECK-NEXT: %[[ORIG_VAL:.*]] = load float, ptr %[[ORIG_PTR]], align 4
// CHECK-NEXT: br label %[[PRIV_BB3:.*]]

// Check contents of the 2nd block in the `copy` region.
// CHECK: [[PRIV_BB3]]:
// CHECK-NEXT: %[[ORIG_VAL2:.*]] = phi float [ %[[ORIG_VAL]], %[[PRIV_BB2]] ]
// CHECK-NEXT: %[[PRIV_ALLOC2:.*]] = phi ptr [ %[[PRIV_ALLOC]], %[[PRIV_BB2]] ]
// CHECK-NEXT: store float %[[ORIG_VAL2]], ptr %[[PRIV_ALLOC2]], align 4
// CHECK-NEXT: br label %[[PRIV_CONT:.*]]

// Check that the privatizer's continuation block yileds the private clone's
// address.
// CHECK: [[PRIV_CONT]]:
// CHECK-NEXT: %[[PRIV_ALLOC3:.*]] = phi ptr [ %[[PRIV_ALLOC2]], %[[PRIV_BB3]] ]
// CHECK-NEXT: br label %[[PAR_REG:.*]]

// Check that the body of the parallel region loads from the private clone.
// CHECK: [[PAR_REG]]:
// CHECK: %{{.*}} = load float, ptr %[[PRIV_ALLOC3]], align 4

omp.private {type = firstprivate} @multi_block.privatizer : !llvm.ptr alloc {
^bb0(%arg0: !llvm.ptr):
%c1 = llvm.mlir.constant(1 : i32) : i32
llvm.br ^bb1(%c1 : i32)

^bb1(%arg1: i32):
%0 = llvm.alloca %arg1 x f32 : (i32) -> !llvm.ptr
omp.yield(%0 : !llvm.ptr)

} copy {
^bb0(%arg0: !llvm.ptr, %arg1: !llvm.ptr):
%0 = llvm.load %arg0 : !llvm.ptr -> f32
llvm.br ^bb1(%0, %arg1 : f32, !llvm.ptr)

^bb1(%arg2: f32, %arg3: !llvm.ptr):
llvm.store %arg2, %arg3 : f32, !llvm.ptr
omp.yield(%arg3 : !llvm.ptr)
}