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[flang] Relax conflicts detection in ElementalAssignBufferization. #143045

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Jun 6, 2025
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[flang] Relax conflicts detection in ElementalAssignBufferization. #143045

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30 changes: 21 additions & 9 deletions flang/lib/Optimizer/HLFIR/Transforms/OptimizedBufferization.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -572,13 +572,11 @@ ElementalAssignBufferization::findMatch(hlfir::ElementalOp elemental) {
// hlfir.assign, check there are no effects which make this unsafe

// keep track of any values written to in the elemental, as these can't be
// read from between the elemental and the assignment
// read from or written to between the elemental and the assignment
mlir::SmallVector<mlir::Value, 1> notToBeAccessedBeforeAssign;
// likewise, values read in the elemental cannot be written to between the
// elemental and the assign
mlir::SmallVector<mlir::Value, 1> notToBeAccessedBeforeAssign;
// any accesses to the array between the array and the assignment means it
// would be unsafe to move the elemental to the assignment
notToBeAccessedBeforeAssign.push_back(match.array);
mlir::SmallVector<mlir::Value, 1> notToBeWrittenBeforeAssign;

// 1) side effects in the elemental body - it isn't sufficient to just look
// for ordered elementals because we also cannot support out of order reads
Expand All @@ -593,10 +591,12 @@ ElementalAssignBufferization::findMatch(hlfir::ElementalOp elemental) {
for (const mlir::MemoryEffects::EffectInstance &effect : *effects) {
mlir::AliasResult res = containsReadOrWriteEffectOn(effect, match.array);
if (res.isNo()) {
if (mlir::isa<mlir::MemoryEffects::Write, mlir::MemoryEffects::Read>(
effect.getEffect()))
if (effect.getValue())
if (effect.getValue()) {
if (mlir::isa<mlir::MemoryEffects::Write>(effect.getEffect()))
notToBeAccessedBeforeAssign.push_back(effect.getValue());
else if (mlir::isa<mlir::MemoryEffects::Read>(effect.getEffect()))
notToBeWrittenBeforeAssign.push_back(effect.getValue());
}

// this is safe in the elemental
continue;
Expand Down Expand Up @@ -669,11 +669,23 @@ ElementalAssignBufferization::findMatch(hlfir::ElementalOp elemental) {
mlir::AliasResult res = containsReadOrWriteEffectOn(effect, val);
if (!res.isNo()) {
LLVM_DEBUG(llvm::dbgs()
<< "diasllowed side-effect: " << effect.getValue() << " for "
<< "disallowed side-effect: " << effect.getValue() << " for "
<< elemental.getLoc() << "\n");
return std::nullopt;
}
}
// Anything that is read inside the elemental can only be safely read
// between the elemental and the assignment.
for (mlir::Value val : notToBeWrittenBeforeAssign) {
mlir::AliasResult res = containsReadOrWriteEffectOn(effect, val);
if (!res.isNo() &&
!mlir::isa<mlir::MemoryEffects::Read>(effect.getEffect())) {
LLVM_DEBUG(llvm::dbgs()
<< "disallowed non-read side-effect: " << effect.getValue()
<< " for " << elemental.getLoc() << "\n");
return std::nullopt;
}
}
}

return match;
Expand Down
59 changes: 59 additions & 0 deletions flang/test/HLFIR/opt-bufferization-tonto.fir
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
// RUN: fir-opt --opt-bufferization %s | FileCheck %s

// tonto case where optimized bufferization conservatively
// did not pull elemental into the assignment due to
// the designate op in between:
// module test
// type my_type
// real, dimension(:,:), pointer :: p => null()
// end type my_type
// contains
// subroutine assign1(self, i)
// type(my_type) :: self
// real, dimension(3) :: ct, q
// integer :: i
// self%p(:,i) = q - ct
// end subroutine assign1
// end module test

// CHECK-LABEL: func.func @_QMtestPassign1(
// CHECK-NOT: hlfir.elemental
// CHECK-NOT: hlfir.assign{{.*}}array
func.func @_QMtestPassign1(%arg0: !fir.ref<!fir.type<_QMtestTmy_type{p:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>> {fir.bindc_name = "self"}, %arg1: !fir.ref<i32> {fir.bindc_name = "i"}) {
%c1 = arith.constant 1 : index
%c0 = arith.constant 0 : index
%c3 = arith.constant 3 : index
%0 = fir.dummy_scope : !fir.dscope
%1 = fir.alloca !fir.array<3xf32> {bindc_name = "ct", uniq_name = "_QMtestFassign1Ect"}
%2 = fir.shape %c3 : (index) -> !fir.shape<1>
%3:2 = hlfir.declare %1(%2) {uniq_name = "_QMtestFassign1Ect"} : (!fir.ref<!fir.array<3xf32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<3xf32>>, !fir.ref<!fir.array<3xf32>>)
%4:2 = hlfir.declare %arg1 dummy_scope %0 {uniq_name = "_QMtestFassign1Ei"} : (!fir.ref<i32>, !fir.dscope) -> (!fir.ref<i32>, !fir.ref<i32>)
%5 = fir.alloca !fir.array<3xf32> {bindc_name = "q", uniq_name = "_QMtestFassign1Eq"}
%6:2 = hlfir.declare %5(%2) {uniq_name = "_QMtestFassign1Eq"} : (!fir.ref<!fir.array<3xf32>>, !fir.shape<1>) -> (!fir.ref<!fir.array<3xf32>>, !fir.ref<!fir.array<3xf32>>)
%7:2 = hlfir.declare %arg0 dummy_scope %0 {uniq_name = "_QMtestFassign1Eself"} : (!fir.ref<!fir.type<_QMtestTmy_type{p:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>>, !fir.dscope) -> (!fir.ref<!fir.type<_QMtestTmy_type{p:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>>, !fir.ref<!fir.type<_QMtestTmy_type{p:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>>)
%8 = hlfir.elemental %2 unordered : (!fir.shape<1>) -> !hlfir.expr<3xf32> {
^bb0(%arg2: index):
%22 = hlfir.designate %6#0 (%arg2) : (!fir.ref<!fir.array<3xf32>>, index) -> !fir.ref<f32>
%23 = hlfir.designate %3#0 (%arg2) : (!fir.ref<!fir.array<3xf32>>, index) -> !fir.ref<f32>
%24 = fir.load %22 : !fir.ref<f32>
%25 = fir.load %23 : !fir.ref<f32>
%26 = arith.subf %24, %25 fastmath<contract> : f32
hlfir.yield_element %26 : f32
}
%9 = hlfir.designate %7#0{"p"} {fortran_attrs = #fir.var_attrs<pointer>} : (!fir.ref<!fir.type<_QMtestTmy_type{p:!fir.box<!fir.ptr<!fir.array<?x?xf32>>>}>>) -> !fir.ref<!fir.box<!fir.ptr<!fir.array<?x?xf32>>>>
%10 = fir.load %9 : !fir.ref<!fir.box<!fir.ptr<!fir.array<?x?xf32>>>>
%11:3 = fir.box_dims %10, %c0 : (!fir.box<!fir.ptr<!fir.array<?x?xf32>>>, index) -> (index, index, index)
%12 = arith.addi %11#0, %11#1 : index
%13 = arith.subi %12, %c1 : index
%14 = arith.subi %13, %11#0 : index
%15 = arith.addi %14, %c1 : index
%16 = arith.cmpi sgt, %15, %c0 : index
%17 = arith.select %16, %15, %c0 : index
%18 = fir.load %4#0 : !fir.ref<i32>
%19 = fir.convert %18 : (i32) -> i64
%20 = fir.shape %17 : (index) -> !fir.shape<1>
%21 = hlfir.designate %10 (%11#0:%13:%c1, %19) shape %20 : (!fir.box<!fir.ptr<!fir.array<?x?xf32>>>, index, index, index, i64, !fir.shape<1>) -> !fir.box<!fir.array<?xf32>>
hlfir.assign %8 to %21 : !hlfir.expr<3xf32>, !fir.box<!fir.array<?xf32>>
hlfir.destroy %8 : !hlfir.expr<3xf32>
return
}
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