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[flang] Use integer arith.max/min operations for max/min lowering. #186466

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Merged
vzakhari merged 5 commits into from
Mar 18, 2026
Merged

[flang] Use integer arith.max/min operations for max/min lowering. #186466

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6740c34
[flang] Use integer arith.max/min operations for max/min lowering.
vzakhari Mar 13, 2026
f74e1f1
Added conversions for unsigned types.
vzakhari Mar 13, 2026
6e40b17
Unused vars.
vzakhari Mar 13, 2026
cba9355
Added lowering tests for unsigned types.
vzakhari Mar 16, 2026
d31e4c1
Added a comment.
vzakhari Mar 17, 2026
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39 changes: 24 additions & 15 deletions flang/lib/Optimizer/Builder/IntrinsicCall.cpp
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Expand Up @@ -8736,12 +8736,6 @@ static mlir::Value genExtremumResult(mlir::Location loc,
fir::FirOpBuilder &builder,
mlir::Value left, mlir::Value right) {
mlir::Type type = left.getType();
mlir::arith::CmpIPredicate integerPredicate =
type.isUnsignedInteger() ? isMax ? mlir::arith::CmpIPredicate::ugt
: mlir::arith::CmpIPredicate::ult
: isMax ? mlir::arith::CmpIPredicate::sgt
: mlir::arith::CmpIPredicate::slt;
mlir::Value pred;
if (fir::isa_real(type)) {
switch (builder.getFPMaxminBehavior()) {
case Fortran::common::FPMaxminBehavior::Portable:
Expand Down Expand Up @@ -8782,26 +8776,41 @@ static mlir::Value genExtremumResult(mlir::Location loc,

llvm_unreachable("unsupported FPMaxminBehavior");
} else if (fir::isa_integer(type)) {
mlir::Value cmpLeft = left;
mlir::Value cmpRight = right;
// It is probably okay to use signed index.maxs/mins, but
// maybe the caller needs to specify signedness.
// There are currently no callers that pass values of index
// type, so just emit a TODO.
if (mlir::isa<mlir::IndexType>(type))
TODO(loc, "extremum for index type");

if (type.isUnsignedInteger()) {
// arith.maxui/minui operands must have singless type.
mlir::Type signlessType = mlir::IntegerType::get(
builder.getContext(), type.getIntOrFloatBitWidth(),
mlir::IntegerType::SignednessSemantics::Signless);
cmpLeft = builder.createConvert(loc, signlessType, left);
cmpRight = builder.createConvert(loc, signlessType, right);
left = builder.createConvert(loc, signlessType, left);
right = builder.createConvert(loc, signlessType, right);

mlir::Value result;
if constexpr (isMax)
result = mlir::arith::MaxUIOp::create(builder, loc, left, right);
else
result = mlir::arith::MinUIOp::create(builder, loc, left, right);

return builder.createConvert(loc, type, result);
} else {
if constexpr (isMax)
return mlir::arith::MaxSIOp::create(builder, loc, left, right);
else
return mlir::arith::MinSIOp::create(builder, loc, left, right);
}
pred = mlir::arith::CmpIOp::create(builder, loc, integerPredicate, cmpLeft,
cmpRight);
} else if (fir::isa_char(type) || fir::isa_char(fir::unwrapRefType(type))) {
// TODO: ! character min and max is tricky because the result
// length is the length of the longest argument!
// So we may need a temp.
TODO(loc, "intrinsic: min and max for CHARACTER");
}
assert(pred && "pred must be defined");

return mlir::arith::SelectOp::create(builder, loc, pred, left, right);
llvm_unreachable("unsupported extremum");
}

// UNLINK
Expand Down
48 changes: 9 additions & 39 deletions flang/lib/Optimizer/HLFIR/Transforms/SimplifyHLFIRIntrinsics.cpp
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Expand Up @@ -382,6 +382,10 @@ template <bool IS_MAX>
static mlir::Value
genMinMaxComparison(mlir::Location loc, fir::FirOpBuilder &builder,
mlir::Value elem, mlir::Value reduction) {
// TODO: there is some opportunity to generalize this code with
// IntrinsicLibrary::genExtremum(), but one have to be careful
// to preserve the NaNs behavior (when needed) that is handled
// here with the three FP comparisons.
if (mlir::isa<mlir::FloatType>(reduction.getType())) {
// For FP reductions we want the first smallest value to be used, that
// is not NaN. A OGL/OLT condition will usually work for this unless all
Expand Down Expand Up @@ -802,6 +806,7 @@ class MinMaxvalAsElementalConverter
this->checkReductions(currentValue);
llvm::SmallVector<mlir::Value> result;
fir::FirOpBuilder &builder = this->builder;
builder.setFPMaxminBehavior(fpMaxminBehavior);
mlir::Location loc = this->loc;
hlfir::Entity elementValue =
hlfir::loadElementAt(loc, builder, array, oneBasedIndices);
Expand Down Expand Up @@ -893,45 +898,10 @@ class MinMaxvalAsElementalConverter
assert(!useIsFirst() &&
"unordered max/min reduction must not use first predicate");

if (mlir::isa<fir::CharacterType>(this->getSourceElementType()))
TODO(loc, "max/minval with CHARACTER type");

if (auto intType =
mlir::dyn_cast<mlir::IntegerType>(this->getSourceElementType())) {
if (intType.isUnsigned())
TODO(loc, "max/minval with UNSIGNED type");

if constexpr (isMax)
return mlir::arith::MaxSIOp::create(builder, loc, elementValue,
currentMinMax);
else
return mlir::arith::MinSIOp::create(builder, loc, elementValue,
currentMinMax);
}

if (fpMaxminBehavior == Fortran::common::FPMaxminBehavior::Extremum) {
if constexpr (isMax)
return mlir::arith::MaximumFOp::create(builder, loc, elementValue,
currentMinMax);
else
return mlir::arith::MinimumFOp::create(builder, loc, elementValue,
currentMinMax);
}

if (fpMaxminBehavior == Fortran::common::FPMaxminBehavior::ExtremeNum ||
(fpMaxminBehavior == Fortran::common::FPMaxminBehavior::Portable &&
mlir::arith::bitEnumContainsAll(
this->getFastMath(), mlir::arith::FastMathFlags::nnan |
mlir::arith::FastMathFlags::nsz))) {
if constexpr (isMax)
return mlir::arith::MaxNumFOp::create(builder, loc, elementValue,
currentMinMax);
else
return mlir::arith::MinNumFOp::create(builder, loc, elementValue,
currentMinMax);
}

llvm_unreachable("unhandled unordered max/min reduction");
if constexpr (isMax)
return fir::genMax(builder, loc, {elementValue, currentMinMax});
else
return fir::genMin(builder, loc, {elementValue, currentMinMax});
}

std::size_t getNumReductions() const { return useIsFirst() ? 2 : 1; }
Expand Down
3 changes: 1 addition & 2 deletions flang/test/Lower/HLFIR/array-ctor-as-elemental.f90
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Expand Up @@ -54,8 +54,7 @@ subroutine test_as_strided_elemental(lb, ub, stride)
! CHECK: %[[VAL_12:.*]] = fir.load %[[VAL_4]]#0 : !fir.ref<i64>
! CHECK: %[[VAL_13:.*]] = arith.divsi %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: %[[VAL_14:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_15:.*]] = arith.cmpi sgt, %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.select %[[VAL_15]], %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.maxsi %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_17:.*]] = arith.addi %[[VAL_6]], %[[VAL_16]] : i64
! CHECK: %[[VAL_18:.*]] = fir.convert %[[VAL_17]] : (i64) -> index
! CHECK: %[[VAL_19:.*]] = fir.shape %[[VAL_18]] : (index) -> !fir.shape<1>
Expand Down
12 changes: 4 additions & 8 deletions flang/test/Lower/HLFIR/array-ctor-as-inlined-temp.f90
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Expand Up @@ -127,8 +127,7 @@ subroutine test_implied_do(n)
! CHECK: %[[VAL_10:.*]] = arith.constant 1 : i64
! CHECK: %[[VAL_11:.*]] = arith.divsi %[[VAL_9]], %[[VAL_10]] : i64
! CHECK: %[[VAL_12:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_13:.*]] = arith.cmpi sgt, %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: %[[VAL_14:.*]] = arith.select %[[VAL_13]], %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: %[[VAL_14:.*]] = arith.maxsi %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: %[[VAL_15:.*]] = arith.muli %[[VAL_4]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.addi %[[VAL_3]], %[[VAL_15]] : i64
! CHECK: %[[VAL_17:.*]] = fir.convert %[[VAL_16]] : (i64) -> index
Expand Down Expand Up @@ -191,8 +190,7 @@ subroutine test_strided_implied_do(lb, ub, stride)
! CHECK: %[[VAL_14:.*]] = fir.load %[[VAL_5]]#0 : !fir.ref<i64>
! CHECK: %[[VAL_15:.*]] = arith.divsi %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_17:.*]] = arith.cmpi sgt, %[[VAL_15]], %[[VAL_16]] : i64
! CHECK: %[[VAL_18:.*]] = arith.select %[[VAL_17]], %[[VAL_15]], %[[VAL_16]] : i64
! CHECK: %[[VAL_18:.*]] = arith.maxsi %[[VAL_15]], %[[VAL_16]] : i64
! CHECK: %[[VAL_19:.*]] = arith.muli %[[VAL_8]], %[[VAL_18]] : i64
! CHECK: %[[VAL_20:.*]] = arith.addi %[[VAL_7]], %[[VAL_19]] : i64
! CHECK: %[[VAL_21:.*]] = fir.convert %[[VAL_20]] : (i64) -> index
Expand Down Expand Up @@ -253,8 +251,7 @@ subroutine test_nested_implied_do(n, m)
! CHECK: %[[VAL_12:.*]] = arith.constant 1 : i64
! CHECK: %[[VAL_13:.*]] = arith.divsi %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: %[[VAL_14:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_15:.*]] = arith.cmpi sgt, %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.select %[[VAL_15]], %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_16:.*]] = arith.maxsi %[[VAL_13]], %[[VAL_14]] : i64
! CHECK: %[[VAL_17:.*]] = arith.addi %[[VAL_6]], %[[VAL_16]] : i64
! CHECK: %[[VAL_18:.*]] = fir.load %[[VAL_4]]#0 : !fir.ref<i64>
! CHECK: %[[VAL_19:.*]] = arith.constant 1 : i64
Expand All @@ -264,8 +261,7 @@ subroutine test_nested_implied_do(n, m)
! CHECK: %[[VAL_23:.*]] = arith.constant 1 : i64
! CHECK: %[[VAL_24:.*]] = arith.divsi %[[VAL_22]], %[[VAL_23]] : i64
! CHECK: %[[VAL_25:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_26:.*]] = arith.cmpi sgt, %[[VAL_24]], %[[VAL_25]] : i64
! CHECK: %[[VAL_27:.*]] = arith.select %[[VAL_26]], %[[VAL_24]], %[[VAL_25]] : i64
! CHECK: %[[VAL_27:.*]] = arith.maxsi %[[VAL_24]], %[[VAL_25]] : i64
! CHECK: %[[VAL_28:.*]] = arith.muli %[[VAL_17]], %[[VAL_27]] : i64
! CHECK: %[[VAL_29:.*]] = arith.addi %[[VAL_5]], %[[VAL_28]] : i64
! CHECK: %[[VAL_30:.*]] = fir.convert %[[VAL_29]] : (i64) -> index
Expand Down
3 changes: 1 addition & 2 deletions flang/test/Lower/HLFIR/binary-ops.f90
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Expand Up @@ -206,8 +206,7 @@ subroutine extremum(c, n, l)
! CHECK: hlfir.declare {{.*}}c"}
! CHECK: %[[VAL_11:.*]] = arith.constant 0 : i64
! CHECK: %[[VAL_12:.*]] = fir.load %{{.*}} : !fir.ref<i64>
! CHECK: %[[VAL_13:.*]] = arith.cmpi sgt, %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: arith.select %[[VAL_13]], %[[VAL_11]], %[[VAL_12]] : i64
! CHECK: arith.maxsi %[[VAL_11]], %[[VAL_12]] : i64

subroutine cmp_int(l, x, y)
logical :: l
Expand Down
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