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[mlir] [arith] Fix ceildivsi lowering in arith-expand #133774

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Apr 2, 2025
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[mlir] [arith] Fix ceildivsi lowering in arith-expand #133774

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f829156
[mlir] Fix ceildivsi lowering in arith-expand
math-fehr Mar 31, 2025
b9e8280
Add integration test for ceildivsi lowering
math-fehr Apr 2, 2025
c392bda
Apply suggestions from code review
math-fehr Apr 2, 2025
1a771e4
Add missing newline
math-fehr Apr 2, 2025
71ffae5
Fix correct newline
math-fehr Apr 2, 2025
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60 changes: 25 additions & 35 deletions mlir/lib/Dialect/Arith/Transforms/ExpandOps.cpp
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Expand Up @@ -58,9 +58,13 @@ struct CeilDivUIOpConverter : public OpRewritePattern<arith::CeilDivUIOp> {
}
};

/// Expands CeilDivSIOp (n, m) into
/// 1) x = (m > 0) ? -1 : 1
/// 2) (n*m>0) ? ((n+x) / m) + 1 : - (-n / m)
/// Expands CeilDivSIOp (a, b) into
/// z = a / b
/// if (z * b != a && (a < 0) == (b < 0)) {
/// return z + 1;
/// } else {
/// return z;
/// }
struct CeilDivSIOpConverter : public OpRewritePattern<arith::CeilDivSIOp> {
using OpRewritePattern::OpRewritePattern;
LogicalResult matchAndRewrite(arith::CeilDivSIOp op,
Expand All @@ -69,43 +73,29 @@ struct CeilDivSIOpConverter : public OpRewritePattern<arith::CeilDivSIOp> {
Type type = op.getType();
Value a = op.getLhs();
Value b = op.getRhs();
Value plusOne = createConst(loc, type, 1, rewriter);

Value zero = createConst(loc, type, 0, rewriter);
Value minusOne = createConst(loc, type, -1, rewriter);
// Compute x = (b>0) ? -1 : 1.
Value compare =
rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::sgt, b, zero);
Value x = rewriter.create<arith::SelectOp>(loc, compare, minusOne, plusOne);
// Compute positive res: 1 + ((x+a)/b).
Value xPlusA = rewriter.create<arith::AddIOp>(loc, x, a);
Value xPlusADivB = rewriter.create<arith::DivSIOp>(loc, xPlusA, b);
Value posRes = rewriter.create<arith::AddIOp>(loc, plusOne, xPlusADivB);
// Compute negative res: - ((-a)/b).
Value minusA = rewriter.create<arith::SubIOp>(loc, zero, a);
Value minusADivB = rewriter.create<arith::DivSIOp>(loc, minusA, b);
Value negRes = rewriter.create<arith::SubIOp>(loc, zero, minusADivB);
// Result is (a*b>0) ? pos result : neg result.
// Note, we want to avoid using a*b because of possible overflow.
// The case that matters are a>0, a==0, a<0, b>0 and b<0. We do
// not particuliarly care if a*b<0 is true or false when b is zero
// as this will result in an illegal divide. So `a*b<0` can be reformulated
// as `(a<0 && b<0) || (a>0 && b>0)' or `(a<0 && b<0) || (a>0 && b>=0)'.
// We pick the first expression here.
Value one = createConst(loc, type, 1, rewriter);

Value quotient = rewriter.create<arith::DivSIOp>(loc, a, b);
Value product = rewriter.create<arith::MulIOp>(loc, quotient, b);
Value notEqualDivisor = rewriter.create<arith::CmpIOp>(
loc, arith::CmpIPredicate::ne, a, product);

Value aNeg =
rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::slt, a, zero);
Value aPos =
rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::sgt, a, zero);
Value bNeg =
rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::slt, b, zero);
Value bPos =
rewriter.create<arith::CmpIOp>(loc, arith::CmpIPredicate::sgt, b, zero);
Value firstTerm = rewriter.create<arith::AndIOp>(loc, aNeg, bNeg);
Value secondTerm = rewriter.create<arith::AndIOp>(loc, aPos, bPos);
Value compareRes =
rewriter.create<arith::OrIOp>(loc, firstTerm, secondTerm);
// Perform substitution and return success.
rewriter.replaceOpWithNewOp<arith::SelectOp>(op, compareRes, posRes,
negRes);

Value signEqual = rewriter.create<arith::CmpIOp>(
loc, arith::CmpIPredicate::eq, aNeg, bNeg);
Value cond =
rewriter.create<arith::AndIOp>(loc, notEqualDivisor, signEqual);

Value quotientPlusOne = rewriter.create<arith::AddIOp>(loc, quotient, one);

rewriter.replaceOpWithNewOp<arith::SelectOp>(op, cond, quotientPlusOne,
quotient);
return success();
}
};
Expand Down
36 changes: 14 additions & 22 deletions mlir/test/Conversion/ArithToLLVM/arith-to-llvm.mlir
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Expand Up @@ -600,28 +600,20 @@ func.func @select_complex(%arg0 : i1, %arg1 : complex<f32>, %arg2 : complex<f32>
// -----

// CHECK-LABEL: @ceildivsi
// CHECK-SAME: %[[ARG0:.*]]: i64) -> i64
func.func @ceildivsi(%arg0 : i64) -> i64 {
// CHECK: %[[CST0:.*]] = llvm.mlir.constant(1 : i64) : i64
// CHECK: %[[CST1:.*]] = llvm.mlir.constant(0 : i64) : i64
// CHECK: %[[CST2:.*]] = llvm.mlir.constant(-1 : i64) : i64
// CHECK: %[[CMP0:.*]] = llvm.icmp "sgt" %[[ARG0]], %[[CST1]] : i64
// CHECK: %[[SEL0:.*]] = llvm.select %[[CMP0]], %[[CST2]], %[[CST0]] : i1, i64
// CHECK: %[[ADD0:.*]] = llvm.add %[[SEL0]], %[[ARG0]] : i64
// CHECK: %[[DIV0:.*]] = llvm.sdiv %[[ADD0]], %[[ARG0]] : i64
// CHECK: %[[ADD1:.*]] = llvm.add %[[DIV0]], %[[CST0]] : i64
// CHECK: %[[SUB0:.*]] = llvm.sub %[[CST1]], %[[ARG0]] : i64
// CHECK: %[[DIV1:.*]] = llvm.sdiv %[[SUB0]], %[[ARG0]] : i64
// CHECK: %[[SUB1:.*]] = llvm.sub %[[CST1]], %[[DIV1]] : i64
// CHECK: %[[CMP1:.*]] = llvm.icmp "slt" %[[ARG0]], %[[CST1]] : i64
// CHECK: %[[CMP2:.*]] = llvm.icmp "sgt" %[[ARG0]], %[[CST1]] : i64
// CHECK: %[[CMP3:.*]] = llvm.icmp "slt" %[[ARG0]], %[[CST1]] : i64
// CHECK: %[[CMP4:.*]] = llvm.icmp "sgt" %[[ARG0]], %[[CST1]] : i64
// CHECK: %[[AND0:.*]] = llvm.and %[[CMP1]], %[[CMP3]] : i1
// CHECK: %[[AND1:.*]] = llvm.and %[[CMP2]], %[[CMP4]] : i1
// CHECK: %[[OR:.*]] = llvm.or %[[AND0]], %[[AND1]] : i1
// CHECK: %[[SEL1:.*]] = llvm.select %[[OR]], %[[ADD1]], %[[SUB1]] : i1, i64
%0 = arith.ceildivsi %arg0, %arg0 : i64
// CHECK-SAME: %[[ARG0:.*]]: i64, %[[ARG1:.*]]: i64) -> i64
func.func @ceildivsi(%arg0 : i64, %arg1 : i64) -> i64 {
// CHECK: %[[ZERO:.+]] = llvm.mlir.constant(0 : i64) : i64
// CHECK: %[[ONE:.+]] = llvm.mlir.constant(1 : i64) : i64
// CHECK: %[[DIV:.+]] = llvm.sdiv %[[ARG0]], %[[ARG1]] : i64
// CHECK: %[[MUL:.+]] = llvm.mul %[[DIV]], %[[ARG1]] : i64
// CHECK: %[[NEXACT:.+]] = llvm.icmp "ne" %[[ARG0]], %[[MUL]] : i64
// CHECK: %[[NNEG:.+]] = llvm.icmp "slt" %[[ARG0]], %[[ZERO]] : i64
// CHECK: %[[MNEG:.+]] = llvm.icmp "slt" %[[ARG1]], %[[ZERO]] : i64
// CHECK: %[[SAMESIGN:.+]] = llvm.icmp "eq" %[[NNEG]], %[[MNEG]] : i1
// CHECK: %[[SHOULDROUND:.+]] = llvm.and %[[NEXACT]], %[[SAMESIGN]] : i1
// CHECK: %[[CEIL:.+]] = llvm.add %[[DIV]], %[[ONE]] : i64
// CHECK: %[[RES:.+]] = llvm.select %[[SHOULDROUND]], %[[CEIL]], %[[DIV]] : i1, i64
%0 = arith.ceildivsi %arg0, %arg1 : i64
return %0: i64
}

Expand Down
57 changes: 21 additions & 36 deletions mlir/test/Dialect/Arith/expand-ops.mlir
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Expand Up @@ -7,25 +7,17 @@ func.func @ceildivi(%arg0: i32, %arg1: i32) -> (i32) {
%res = arith.ceildivsi %arg0, %arg1 : i32
return %res : i32

// CHECK: [[ONE:%.+]] = arith.constant 1 : i32
// CHECK: [[ZERO:%.+]] = arith.constant 0 : i32
// CHECK: [[MINONE:%.+]] = arith.constant -1 : i32
// CHECK: [[CMP1:%.+]] = arith.cmpi sgt, [[ARG1]], [[ZERO]] : i32
// CHECK: [[X:%.+]] = arith.select [[CMP1]], [[MINONE]], [[ONE]] : i32
// CHECK: [[TRUE1:%.+]] = arith.addi [[X]], [[ARG0]] : i32
// CHECK: [[TRUE2:%.+]] = arith.divsi [[TRUE1]], [[ARG1]] : i32
// CHECK: [[TRUE3:%.+]] = arith.addi [[ONE]], [[TRUE2]] : i32
// CHECK: [[FALSE1:%.+]] = arith.subi [[ZERO]], [[ARG0]] : i32
// CHECK: [[FALSE2:%.+]] = arith.divsi [[FALSE1]], [[ARG1]] : i32
// CHECK: [[FALSE3:%.+]] = arith.subi [[ZERO]], [[FALSE2]] : i32
// CHECK: [[NNEG:%.+]] = arith.cmpi slt, [[ARG0]], [[ZERO]] : i32
// CHECK: [[NPOS:%.+]] = arith.cmpi sgt, [[ARG0]], [[ZERO]] : i32
// CHECK: [[MNEG:%.+]] = arith.cmpi slt, [[ARG1]], [[ZERO]] : i32
// CHECK: [[MPOS:%.+]] = arith.cmpi sgt, [[ARG1]], [[ZERO]] : i32
// CHECK: [[TERM1:%.+]] = arith.andi [[NNEG]], [[MNEG]] : i1
// CHECK: [[TERM2:%.+]] = arith.andi [[NPOS]], [[MPOS]] : i1
// CHECK: [[CMP2:%.+]] = arith.ori [[TERM1]], [[TERM2]] : i1
// CHECK: [[RES:%.+]] = arith.select [[CMP2]], [[TRUE3]], [[FALSE3]] : i32
// CHECK: [[ONE:%.+]] = arith.constant 1 : i32
// CHECK: [[DIV:%.+]] = arith.divsi %arg0, %arg1 : i32
// CHECK: [[MUL:%.+]] = arith.muli [[DIV]], %arg1 : i32
// CHECK: [[NEXACT:%.+]] = arith.cmpi ne, %arg0, [[MUL]] : i32
// CHECK: [[NNEG:%.+]] = arith.cmpi slt, %arg0, [[ZERO]] : i32
// CHECK: [[MNEG:%.+]] = arith.cmpi slt, %arg1, [[ZERO]] : i32
// CHECK: [[SAMESIGN:%.+]] = arith.cmpi eq, [[NNEG]], [[MNEG]] : i1
// CHECK: [[SHOULDROUND:%.+]] = arith.andi [[NEXACT]], [[SAMESIGN]] : i1
// CHECK: [[CEIL:%.+]] = arith.addi [[DIV]], [[ONE]] : i32
// CHECK: [[RES:%.+]] = arith.select [[SHOULDROUND]], [[CEIL]], [[DIV]] : i32
}

// -----
Expand All @@ -37,25 +29,18 @@ func.func @ceildivi_index(%arg0: index, %arg1: index) -> (index) {
%res = arith.ceildivsi %arg0, %arg1 : index
return %res : index

// CHECK: [[ONE:%.+]] = arith.constant 1 : index
// CHECK: [[ZERO:%.+]] = arith.constant 0 : index
// CHECK: [[MINONE:%.+]] = arith.constant -1 : index
// CHECK: [[CMP1:%.+]] = arith.cmpi sgt, [[ARG1]], [[ZERO]] : index
// CHECK: [[X:%.+]] = arith.select [[CMP1]], [[MINONE]], [[ONE]] : index
// CHECK: [[TRUE1:%.+]] = arith.addi [[X]], [[ARG0]] : index
// CHECK: [[TRUE2:%.+]] = arith.divsi [[TRUE1]], [[ARG1]] : index
// CHECK: [[TRUE3:%.+]] = arith.addi [[ONE]], [[TRUE2]] : index
// CHECK: [[FALSE1:%.+]] = arith.subi [[ZERO]], [[ARG0]] : index
// CHECK: [[FALSE2:%.+]] = arith.divsi [[FALSE1]], [[ARG1]] : index
// CHECK: [[FALSE3:%.+]] = arith.subi [[ZERO]], [[FALSE2]] : index
// CHECK: [[NNEG:%.+]] = arith.cmpi slt, [[ARG0]], [[ZERO]] : index
// CHECK: [[NPOS:%.+]] = arith.cmpi sgt, [[ARG0]], [[ZERO]] : index
// CHECK: [[MNEG:%.+]] = arith.cmpi slt, [[ARG1]], [[ZERO]] : index
// CHECK: [[MPOS:%.+]] = arith.cmpi sgt, [[ARG1]], [[ZERO]] : index
// CHECK: [[TERM1:%.+]] = arith.andi [[NNEG]], [[MNEG]] : i1
// CHECK: [[TERM2:%.+]] = arith.andi [[NPOS]], [[MPOS]] : i1
// CHECK: [[CMP2:%.+]] = arith.ori [[TERM1]], [[TERM2]] : i1
// CHECK: [[RES:%.+]] = arith.select [[CMP2]], [[TRUE3]], [[FALSE3]] : index
// CHECK: [[ONE:%.+]] = arith.constant 1 : index
// CHECK: [[DIV:%.+]] = arith.divsi %arg0, %arg1 : index
// CHECK: [[MUL:%.+]] = arith.muli [[DIV]], %arg1 : index
// CHECK: [[NEXACT:%.+]] = arith.cmpi ne, %arg0, [[MUL]] : index
// CHECK: [[NNEG:%.+]] = arith.cmpi slt, %arg0, [[ZERO]] : index
// CHECK: [[MNEG:%.+]] = arith.cmpi slt, %arg1, [[ZERO]] : index
// CHECK: [[SAMESIGN:%.+]] = arith.cmpi eq, [[NNEG]], [[MNEG]] : i1
// CHECK: [[SHOULDROUND:%.+]] = arith.andi [[NEXACT]], [[SAMESIGN]] : i1
// CHECK: [[CEIL:%.+]] = arith.addi [[DIV]], [[ONE]] : index
// CHECK: [[RES:%.+]] = arith.select [[SHOULDROUND]], [[CEIL]], [[DIV]] : index

}

// -----
Expand Down
106 changes: 106 additions & 0 deletions mlir/test/Integration/Dialect/Arith/CPU/test-arith-expand-ceildivsi.mlir
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@@ -0,0 +1,106 @@
// Check that the ceildivsi lowering is correct.
// We do not check any poison or UB values, as it is not possible to catch them.

// RUN: mlir-opt %s --convert-vector-to-llvm \
// RUN: --convert-func-to-llvm --convert-arith-to-llvm | \
// RUN: mlir-runner -e entry --entry-point-result=void \
// RUN: --shared-libs=%mlir_c_runner_utils | \
// RUN: FileCheck %s --match-full-lines

func.func @check_ceildivsi(%lhs : i32, %rhs : i32) -> () {
%res = arith.ceildivsi %lhs, %rhs : i32
vector.print %res : i32
return
}

func.func @entry() {
%int_min = arith.constant -2147483648 : i32
%int_max = arith.constant 2147483647 : i32
%minus_three = arith.constant -3 : i32
%minus_two = arith.constant -2 : i32
%minus_one = arith.constant -1 : i32
%zero = arith.constant 0 : i32
%one = arith.constant 1 : i32
%two = arith.constant 2 : i32
%three = arith.constant 3 : i32

// INT_MAX divided by values.
// CHECK: 1
func.call @check_ceildivsi(%int_max, %int_max) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%int_max, %int_min) : (i32, i32) -> ()
// CHECK-NEXT: -2147483647
func.call @check_ceildivsi(%int_max, %minus_one) : (i32, i32) -> ()
// CHECK-NEXT: -1073741823
func.call @check_ceildivsi(%int_max, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: 2147483647
func.call @check_ceildivsi(%int_max, %one) : (i32, i32) -> ()
// CHECK-NEXT: 1073741824
func.call @check_ceildivsi(%int_max, %two) : (i32, i32) -> ()

// INT_MIN divided by values.
// We do not check the result of INT_MIN divided by -1, as it is UB.
// CHECK-NEXT: 1
func.call @check_ceildivsi(%int_min, %int_min) : (i32, i32) -> ()
// CHECK-NEXT: -1
func.call @check_ceildivsi(%int_min, %int_max) : (i32, i32) -> ()
// CHECK-NEXT: 1073741824
func.call @check_ceildivsi(%int_min, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: -2147483648
func.call @check_ceildivsi(%int_min, %one) : (i32, i32) -> ()
// CHECK-NEXT: -1073741824
func.call @check_ceildivsi(%int_min, %two) : (i32, i32) -> ()

// Divide values by INT_MIN.
// CHECK-NEXT: 0
func.call @check_ceildivsi(%one, %int_min) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%two, %int_min) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%minus_one, %int_min) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%minus_two, %int_min) : (i32, i32) -> ()

// Divide values by INT_MAX.
// CHECK-NEXT: 1
func.call @check_ceildivsi(%one, %int_max) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%two, %int_max) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%minus_one, %int_max) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%minus_two, %int_max) : (i32, i32) -> ()

// Check divisions by 2.
// CHECK-NEXT: -1
func.call @check_ceildivsi(%minus_three, %two) : (i32, i32) -> ()
// CHECK-NEXT: -1
func.call @check_ceildivsi(%minus_two, %two) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%minus_one, %two) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%zero, %two) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%one, %two) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%two, %two) : (i32, i32) -> ()
// CHECK-NEXT: 2
func.call @check_ceildivsi(%three, %two) : (i32, i32) -> ()

// Check divisions by -2.
// CHECK-NEXT: 2
func.call @check_ceildivsi(%minus_three, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%minus_two, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: 1
func.call @check_ceildivsi(%minus_one, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%zero, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: 0
func.call @check_ceildivsi(%one, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: -1
func.call @check_ceildivsi(%two, %minus_two) : (i32, i32) -> ()
// CHECK-NEXT: -1
func.call @check_ceildivsi(%three, %minus_two) : (i32, i32) -> ()
return
}