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[flang] Fix optimization of array assignments after #146408 #147371

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Merged
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Jul 8, 2025
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[flang] Fix optimization of array assignments after #146408 #147371

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11 changes: 5 additions & 6 deletions flang/lib/Optimizer/HLFIR/Transforms/OptimizedBufferization.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -805,13 +805,12 @@ llvm::LogicalResult BroadcastAssignBufferization::matchAndRewrite(
shape, /*slice=*/mlir::Value{});
} else {
// Array references must have fixed shape, when used in assignments.
auto refTy = mlir::cast<fir::ReferenceType>(lhs.getType());
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@jeanPerier jeanPerier Jul 8, 2025

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I think it is slightly unsafe to assume this cannot be a fir.heap/fir.ptr. Nothing prevents these types from describing constant shaped compiler generated objects. Please use fir::unwrapRefType() instead.

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@luporl luporl Jul 8, 2025

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Thanks for the review.

On line 786 there is a call to hlfir::derefPointersAndAllocatables:
lhs = hlfir::derefPointersAndAllocatables(loc, builder, lhs);
Shouldn't it handle fir.heap/fir.ptr already?

Also, after getting the flat array reference type, lhs is converted to it. Would this convert be valid for fir.heap/fir.ptr?

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@eugeneepshteyn eugeneepshteyn Jul 8, 2025

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Would it be possible to submit this PR soon and do a follow-up with any additional changes? This issue blocks internal testing of some apps.

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@luporl luporl Jul 8, 2025

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Since it is already approved and blocking testing, I believe it's OK to merge it now.
As mentioned, I can make any necessary changes in a follow-up PR.

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@luporl luporl Jul 9, 2025

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Now I understand @jeanPerier's comment.
Even after calling hlfir::derefPointersAndAllocatables the resulting type may still be a fir.heap/fir.ptr.
They can be converted to a fir.ref.

It seems hlfir::derefPointersAndAllocatables dereferences other pointer types, such as !fir.ref<!fir.box<!fir.ptr<!fir.array...>>>, generated from Fortran pointers, but not pointers directly to arrays, such as !fir.ptr<!fir.array...>, that may appear when equivalence is used.

I'll prepare a follow-up PR with this change.

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@eugeneepshteyn eugeneepshteyn Jul 9, 2025

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Ok, lesson learned: "always listen to Jean" :)

auto seqTy = mlir::cast<fir::SequenceType>(refTy.getElementType());
llvm::ArrayRef<int64_t> fixedShape = seqTy.getShape();
int64_t flatExtent = 1;
for (const mlir::Value &extent : extents) {
mlir::Operation *op = extent.getDefiningOp();
assert(op && "no defining operation for constant array extent");
flatExtent *= fir::toInt(mlir::cast<mlir::arith::ConstantOp>(*op));
}

for (int64_t extent : fixedShape)
flatExtent *= extent;
flatArrayType =
fir::ReferenceType::get(fir::SequenceType::get({flatExtent}, eleTy));
flatArray = builder.createConvert(loc, flatArrayType, flatArray);
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29 changes: 29 additions & 0 deletions flang/test/HLFIR/opt-scalar-assign.fir
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Expand Up @@ -155,3 +155,32 @@ func.func @_QPtest6(%arg0: !fir.ref<!fir.box<!fir.heap<!fir.array<?x?xi32>>>> {f
// CHECK: }
// CHECK: return
// CHECK: }

func.func @_QQmain() {
return
}

func.func private @_QFPtest7(%arg0: !fir.ref<tuple<!fir.box<!fir.array<2x2xi32>>>> {fir.host_assoc}) attributes {fir.host_symbol = @_QQmain, llvm.linkage = #llvm.linkage<internal>} {
%0 = fir.dummy_scope : !fir.dscope
%c0_i32 = arith.constant 0 : i32
%1 = fir.coordinate_of %arg0, %c0_i32 : (!fir.ref<tuple<!fir.box<!fir.array<2x2xi32>>>>, i32) -> !fir.ref<!fir.box<!fir.array<2x2xi32>>>
%2 = fir.load %1 : !fir.ref<!fir.box<!fir.array<2x2xi32>>>
%3 = fir.box_addr %2 : (!fir.box<!fir.array<2x2xi32>>) -> !fir.ref<!fir.array<2x2xi32>>
%c0 = arith.constant 0 : index
%4:3 = fir.box_dims %2, %c0 : (!fir.box<!fir.array<2x2xi32>>, index) -> (index, index, index)
%c1 = arith.constant 1 : index
%5:3 = fir.box_dims %2, %c1 : (!fir.box<!fir.array<2x2xi32>>, index) -> (index, index, index)
%6 = fir.shape %4#1, %5#1 : (index, index) -> !fir.shape<2>
%7:2 = hlfir.declare %3(%6) {fortran_attrs = #fir.var_attrs<host_assoc>, uniq_name = "_QFEa"} : (!fir.ref<!fir.array<2x2xi32>>, !fir.shape<2>) -> (!fir.ref<!fir.array<2x2xi32>>, !fir.ref<!fir.array<2x2xi32>>)
%c0_i32_0 = arith.constant 0 : i32
hlfir.assign %c0_i32_0 to %7#0 : i32, !fir.ref<!fir.array<2x2xi32>>
return
}

// CHECK-LABEL: func.func private @_QFPtest7({{.*}}) {{.*}} {
// CHECK: %[[VAL_0:.*]] = arith.constant 0 : i32
// CHECK: fir.do_loop %[[VAL_1:.*]] = %{{.*}} to %{{.*}} step %{{.*}} unordered {
// CHECK: %[[VAL_2:.*]] = hlfir.designate %{{.*}} (%[[VAL_1]]) : (!fir.ref<!fir.array<4xi32>>, index) -> !fir.ref<i32>
// CHECK: hlfir.assign %[[VAL_0]] to %[[VAL_2]] : i32, !fir.ref<i32>
// CHECK: }
// CHECK: }
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