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[arith][mlir] Fixed a bug in CeilDiv with neg values #90855

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[arith][mlir] Fixed a bug in CeilDiv with neg values #90855

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ff39236
[arith][mlir] Fixed a bug in CeilDiv with neg values
bviyer May 2, 2024
7214f24
Added more information to a comment
bviyer May 3, 2024
941e961
Fixed clang-format error
bviyer May 3, 2024
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36 changes: 19 additions & 17 deletions mlir/lib/Dialect/Arith/IR/ArithOps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -652,16 +652,18 @@ OpFoldResult arith::CeilDivSIOp::fold(FoldAdaptor adaptor) {
APInt posB = zero.ssub_ov(b, overflowOrDiv0);
return signedCeilNonnegInputs(posA, posB, overflowOrDiv0);
}
if (!aGtZero && bGtZero) {
// A is negative, b is positive, return - ( -a / b).
APInt posA = zero.ssub_ov(a, overflowOrDiv0);
APInt div = posA.sdiv_ov(b, overflowOrDiv0);
return zero.ssub_ov(div, overflowOrDiv0);
}
// A is positive, b is negative, return - (a / -b).
APInt posB = zero.ssub_ov(b, overflowOrDiv0);
APInt div = a.sdiv_ov(posB, overflowOrDiv0);
return zero.ssub_ov(div, overflowOrDiv0);
// If either divisor or dividend is negative, then take their absolute
// value and then do a normal signedCeil Division, but add 1 to bring
// the quotient down. In essense, Ceil Division with one of the values
// negative works like a floorDivision with negated quotient.
// Mathematically, -1 * (abs(a)-1/abs(b) + 1) + 1, which after factoring
// out -1 yields -1 * [abs(a)-1/abs(b) + 1 - 1]. This is implemented
// below.
APInt posA = aGtZero ? a : zero.ssub_ov(a, overflowOrDiv0);
APInt posB = bGtZero ? b : zero.ssub_ov(b, overflowOrDiv0);
APInt div = signedCeilNonnegInputs(posA, posB, overflowOrDiv0);
APInt res = div.ssub_ov(APInt::getOneBitSet(bits, 0), overflowOrDiv0);
return zero.ssub_ov(res, overflowOrDiv0);
});

return overflowOrDiv0 ? Attribute() : result;
Expand Down Expand Up @@ -2260,12 +2262,12 @@ OpFoldResult arith::SelectOp::fold(FoldAdaptor adaptor) {

// Constant-fold constant operands over non-splat constant condition.
// select %cst_vec, %cst0, %cst1 => %cst2
if (auto cond =
llvm::dyn_cast_if_present<DenseElementsAttr>(adaptor.getCondition())) {
if (auto lhs =
llvm::dyn_cast_if_present<DenseElementsAttr>(adaptor.getTrueValue())) {
if (auto rhs =
llvm::dyn_cast_if_present<DenseElementsAttr>(adaptor.getFalseValue())) {
if (auto cond = llvm::dyn_cast_if_present<DenseElementsAttr>(
adaptor.getCondition())) {
if (auto lhs = llvm::dyn_cast_if_present<DenseElementsAttr>(
adaptor.getTrueValue())) {
if (auto rhs = llvm::dyn_cast_if_present<DenseElementsAttr>(
adaptor.getFalseValue())) {
SmallVector<Attribute> results;
results.reserve(static_cast<size_t>(cond.getNumElements()));
auto condVals = llvm::make_range(cond.value_begin<BoolAttr>(),
Expand Down Expand Up @@ -2520,7 +2522,7 @@ Value mlir::arith::getReductionOp(AtomicRMWKind op, OpBuilder &builder,
return builder.create<arith::MaximumFOp>(loc, lhs, rhs);
case AtomicRMWKind::minimumf:
return builder.create<arith::MinimumFOp>(loc, lhs, rhs);
case AtomicRMWKind::maxnumf:
case AtomicRMWKind::maxnumf:
return builder.create<arith::MaxNumFOp>(loc, lhs, rhs);
case AtomicRMWKind::minnumf:
return builder.create<arith::MinNumFOp>(loc, lhs, rhs);
Expand Down
11 changes: 11 additions & 0 deletions mlir/test/Transforms/constant-fold.mlir
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Original file line number Diff line number Diff line change
Expand Up @@ -478,6 +478,17 @@ func.func @simple_arith.ceildivsi() -> (i32, i32, i32, i32, i32) {

// -----

// CHECK-LABEL: simple_arith.ceildivsi_i8
func.func @simple_arith.ceildivsi_i8() -> (i8) {
%0 = arith.constant 7 : i8
%1 = arith.constant -128 : i8
// CHECK-NEXT: arith.constant -18
%2 = arith.ceildivsi %1, %0 : i8
return %2 : i8
}

// -----

// CHECK-LABEL: func @simple_arith.ceildivui
func.func @simple_arith.ceildivui() -> (i32, i32, i32, i32, i32) {
// CHECK-DAG: [[C0:%.+]] = arith.constant 0
Expand Down
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