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Fix side effects for LLVM integer operations (udiv, sdiv) incorrectly marked as Pure #166648

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Nov 17, 2025
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Fix side effects for LLVM integer operations (udiv, sdiv) incorrectly marked as Pure #166648

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33 changes: 18 additions & 15 deletions mlir/include/mlir/Dialect/LLVMIR/LLVMOps.td
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ class LLVM_TerminatorOp<string mnemonic, list<Trait> traits = []> :
class LLVM_ArithmeticOpBase<Type type, string mnemonic,
string instName, list<Trait> traits = []> :
LLVM_Op<mnemonic,
!listconcat([Pure, SameOperandsAndResultType], traits)>,
!listconcat([SameOperandsAndResultType, NoMemoryEffect], traits)>,
LLVM_Builder<"$res = builder.Create" # instName # "($lhs, $rhs);"> {
dag commonArgs = (ins LLVM_ScalarOrVectorOf<type>:$lhs,
LLVM_ScalarOrVectorOf<type>:$rhs);
Expand Down Expand Up @@ -116,7 +116,8 @@ class LLVM_IntArithmeticOpWithDisjointFlag<string mnemonic, string instName,
class LLVM_FloatArithmeticOp<string mnemonic, string instName,
list<Trait> traits = []> :
LLVM_ArithmeticOpBase<LLVM_AnyFloat, mnemonic, instName,
!listconcat([DeclareOpInterfaceMethods<FastmathFlagsInterface>], traits)> {
!listconcat([DeclareOpInterfaceMethods<FastmathFlagsInterface>, Pure],
traits)> {
dag fmfArg = (
ins DefaultValuedAttr<LLVM_FastmathFlagsAttr, "{}">:$fastmathFlags);
let arguments = !con(commonArgs, fmfArg);
Expand Down Expand Up @@ -149,24 +150,26 @@ class LLVM_UnaryFloatArithmeticOp<Type type, string mnemonic,

// Integer binary operations.
def LLVM_AddOp : LLVM_IntArithmeticOpWithOverflowFlag<"add", "Add",
[Commutative]>;
def LLVM_SubOp : LLVM_IntArithmeticOpWithOverflowFlag<"sub", "Sub", []>;
[Commutative, Pure]>;
def LLVM_SubOp : LLVM_IntArithmeticOpWithOverflowFlag<"sub", "Sub", [Pure]>;
def LLVM_MulOp : LLVM_IntArithmeticOpWithOverflowFlag<"mul", "Mul",
[Commutative]>;
def LLVM_UDivOp : LLVM_IntArithmeticOpWithExactFlag<"udiv", "UDiv">;
def LLVM_SDivOp : LLVM_IntArithmeticOpWithExactFlag<"sdiv", "SDiv">;
def LLVM_URemOp : LLVM_IntArithmeticOp<"urem", "URem">;
def LLVM_SRemOp : LLVM_IntArithmeticOp<"srem", "SRem">;
def LLVM_AndOp : LLVM_IntArithmeticOp<"and", "And">;
def LLVM_OrOp : LLVM_IntArithmeticOpWithDisjointFlag<"or", "Or"> {
[Commutative, Pure]>;
def LLVM_UDivOp : LLVM_IntArithmeticOpWithExactFlag<"udiv", "UDiv",
[DeclareOpInterfaceMethods<ConditionallySpeculatable>]>;
def LLVM_SDivOp : LLVM_IntArithmeticOpWithExactFlag<"sdiv", "SDiv",
[DeclareOpInterfaceMethods<ConditionallySpeculatable>]>;
def LLVM_URemOp : LLVM_IntArithmeticOp<"urem", "URem", [Pure]>;
def LLVM_SRemOp : LLVM_IntArithmeticOp<"srem", "SRem", [Pure]>;
def LLVM_AndOp : LLVM_IntArithmeticOp<"and", "And", [Pure]>;
def LLVM_OrOp : LLVM_IntArithmeticOpWithDisjointFlag<"or", "Or", [Pure]> {
let hasFolder = 1;
}
def LLVM_XOrOp : LLVM_IntArithmeticOp<"xor", "Xor">;
def LLVM_ShlOp : LLVM_IntArithmeticOpWithOverflowFlag<"shl", "Shl", []> {
def LLVM_XOrOp : LLVM_IntArithmeticOp<"xor", "Xor", [Pure]>;
def LLVM_ShlOp : LLVM_IntArithmeticOpWithOverflowFlag<"shl", "Shl", [Pure]> {
let hasFolder = 1;
}
def LLVM_LShrOp : LLVM_IntArithmeticOpWithExactFlag<"lshr", "LShr">;
def LLVM_AShrOp : LLVM_IntArithmeticOpWithExactFlag<"ashr", "AShr">;
def LLVM_LShrOp : LLVM_IntArithmeticOpWithExactFlag<"lshr", "LShr", [Pure]>;
def LLVM_AShrOp : LLVM_IntArithmeticOpWithExactFlag<"ashr", "AShr", [Pure]>;

// Base class for compare operations. A compare operation takes two operands
// of the same type and returns a boolean result. If the operands are
Expand Down
28 changes: 28 additions & 0 deletions mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp
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Expand Up @@ -4225,6 +4225,34 @@ LogicalResult InlineAsmOp::verify() {
return success();
}

//===----------------------------------------------------------------------===//
// UDivOp
//===----------------------------------------------------------------------===//
Speculation::Speculatability UDivOp::getSpeculatability() {
// X / 0 => UB
Value divisor = getRhs();
if (matchPattern(divisor, m_IntRangeWithoutZeroU()))
return Speculation::Speculatable;

return Speculation::NotSpeculatable;
}

//===----------------------------------------------------------------------===//
// SDivOp
//===----------------------------------------------------------------------===//
Speculation::Speculatability SDivOp::getSpeculatability() {
// This function conservatively assumes that all signed division by -1 are
// not speculatable.
// X / 0 => UB
// INT_MIN / -1 => UB
Value divisor = getRhs();
if (matchPattern(divisor, m_IntRangeWithoutZeroS()) &&
matchPattern(divisor, m_IntRangeWithoutNegOneS()))
return Speculation::Speculatable;

return Speculation::NotSpeculatable;
}

//===----------------------------------------------------------------------===//
// LLVMDialect initialization, type parsing, and registration.
//===----------------------------------------------------------------------===//
Expand Down
145 changes: 145 additions & 0 deletions mlir/test/Transforms/loop-invariant-code-motion.mlir
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Expand Up @@ -880,6 +880,18 @@ func.func @no_speculate_divui(
return
}

func.func @no_speculate_udiv(
// CHECK-LABEL: @no_speculate_udiv(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.udiv
%val = llvm.udiv %num, %denom : i32
}

return
}

func.func @no_speculate_divsi(
// CHECK-LABEL: @no_speculate_divsi(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
Expand All @@ -892,6 +904,18 @@ func.func @no_speculate_divsi(
return
}

func.func @no_speculate_sdiv(
// CHECK-LABEL: @no_speculate_sdiv(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.sdiv
%val = llvm.sdiv %num, %denom : i32
}

return
}

func.func @no_speculate_ceildivui(
// CHECK-LABEL: @no_speculate_ceildivui(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
Expand Down Expand Up @@ -928,6 +952,18 @@ func.func @no_speculate_divui_const(%num: i32, %lb: index, %ub: index, %step: in
return
}

func.func @no_speculate_udiv_const(%num: i32, %lb: index, %ub: index, %step: index) {
// CHECK-LABEL: @no_speculate_udiv_const(
%c0 = arith.constant 0 : i32
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.udiv
%val = llvm.udiv %num, %c0 : i32
}

return
}

func.func @speculate_divui_const(
// CHECK-LABEL: @speculate_divui_const(
%num: i32, %lb: index, %ub: index, %step: index) {
Expand All @@ -941,6 +977,19 @@ func.func @speculate_divui_const(
return
}

func.func @speculate_udiv_const(
// CHECK-LABEL: @speculate_udiv_const(
%num: i32, %lb: index, %ub: index, %step: index) {
%c5 = llvm.mlir.constant(5 : i32) : i32
// CHECK: llvm.udiv
// CHECK: scf.for
scf.for %i = %lb to %ub step %step {
%val = llvm.udiv %num, %c5 : i32
}

return
}

func.func @no_speculate_ceildivui_const(%num: i32, %lb: index, %ub: index, %step: index) {
// CHECK-LABEL: @no_speculate_ceildivui_const(
%c0 = arith.constant 0 : i32
Expand Down Expand Up @@ -979,6 +1028,19 @@ func.func @no_speculate_divsi_const0(
return
}

func.func @no_speculate_sdiv_const0(
// CHECK-LABEL: @no_speculate_sdiv_const0(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
%c0 = arith.constant 0 : i32
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.sdiv
%val = llvm.sdiv %num, %c0 : i32
}

return
}

func.func @no_speculate_divsi_const_minus1(
// CHECK-LABEL: @no_speculate_divsi_const_minus1(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
Expand All @@ -992,6 +1054,19 @@ func.func @no_speculate_divsi_const_minus1(
return
}

func.func @no_speculate_sdiv_const_minus1(
// CHECK-LABEL: @no_speculate_sdiv_const_minus1(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
%cm1 = arith.constant -1 : i32
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.sdiv
%val = llvm.sdiv %num, %cm1 : i32
}

return
}

func.func @speculate_divsi_const(
// CHECK-LABEL: @speculate_divsi_const(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
Expand All @@ -1005,6 +1080,19 @@ func.func @speculate_divsi_const(
return
}

func.func @speculate_sdiv_const(
// CHECK-LABEL: @speculate_sdiv_const(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
%c5 = arith.constant 5 : i32
scf.for %i = %lb to %ub step %step {
// CHECK: llvm.sdiv
// CHECK: scf.for
%val = llvm.sdiv %num, %c5 : i32
}

return
}

func.func @no_speculate_ceildivsi_const0(
// CHECK-LABEL: @no_speculate_ceildivsi_const0(
%num: i32, %denom: i32, %lb: index, %ub: index, %step: index) {
Expand Down Expand Up @@ -1057,6 +1145,19 @@ func.func @no_speculate_divui_range(
return
}

func.func @no_speculate_udiv_range(
// CHECK-LABEL: @no_speculate_udiv_range(
%num: i8, %lb: index, %ub: index, %step: index) {
%denom = test.with_bounds {smax = 127 : i8, smin = -128 : i8, umax = 255 : i8, umin = 0 : i8} : i8
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK: llvm.udiv
%val = llvm.udiv %num, %denom : i8
}

return
}

func.func @no_speculate_divsi_range(
// CHECK-LABEL: @no_speculate_divsi_range(
%num: i8, %lb: index, %ub: index, %step: index) {
Expand All @@ -1072,6 +1173,21 @@ func.func @no_speculate_divsi_range(
return
}

func.func @no_speculate_sdiv_range(
// CHECK-LABEL: @no_speculate_sdiv_range(
%num: i8, %lb: index, %ub: index, %step: index) {
%denom0 = test.with_bounds {smax = -1: i8, smin = -128 : i8, umax = 255 : i8, umin = 0 : i8} : i8
%denom1 = test.with_bounds {smax = 127 : i8, smin = 0 : i8, umax = 255 : i8, umin = 0 : i8} : i8
scf.for %i = %lb to %ub step %step {
// CHECK: scf.for
// CHECK-COUNT-2: llvm.sdiv
%val0 = llvm.sdiv %num, %denom0 : i8
%val1 = llvm.sdiv %num, %denom1 : i8
}

return
}

func.func @no_speculate_ceildivui_range(
// CHECK-LABEL: @no_speculate_ceildivui_range(
%num: i8, %lb: index, %ub: index, %step: index) {
Expand Down Expand Up @@ -1113,6 +1229,19 @@ func.func @speculate_divui_range(
return
}

func.func @speculate_udiv_range(
// CHECK-LABEL: @speculate_udiv_range(
%num: i8, %lb: index, %ub: index, %step: index) {
%denom = test.with_bounds {smax = 127 : i8, smin = -128 : i8, umax = 255 : i8, umin = 1 : i8} : i8
scf.for %i = %lb to %ub step %step {
// CHECK: llvm.udiv
// CHECK: scf.for
%val = llvm.udiv %num, %denom : i8
}

return
}

func.func @speculate_divsi_range(
// CHECK-LABEL: @speculate_divsi_range(
%num: i8, %lb: index, %ub: index, %step: index) {
Expand All @@ -1129,6 +1258,22 @@ func.func @speculate_divsi_range(
return
}

func.func @speculate_sdiv_range(
// CHECK-LABEL: @speculate_sdiv_range(
%num: i8, %lb: index, %ub: index, %step: index) {
%denom0 = test.with_bounds {smax = 127 : i8, smin = 1 : i8, umax = 255 : i8, umin = 0 : i8} : i8
%denom1 = test.with_bounds {smax = -2 : i8, smin = -128 : i8, umax = 255 : i8, umin = 0 : i8} : i8
scf.for %i = %lb to %ub step %step {
// CHECK-COUNT-2: llvm.sdiv
// CHECK: scf.for
%val0 = llvm.sdiv %num, %denom0 : i8
%val1 = llvm.sdiv %num, %denom1 : i8

}

return
}

func.func @speculate_ceildivui_range(
// CHECK-LABEL: @speculate_ceildivui_range(
%num: i8, %lb: index, %ub: index, %step: index) {
Expand Down
1 change: 1 addition & 0 deletions mlir/unittests/Dialect/LLVMIR/CMakeLists.txt
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Expand Up @@ -4,4 +4,5 @@ add_mlir_unittest(MLIRLLVMIRTests
mlir_target_link_libraries(MLIRLLVMIRTests
PRIVATE
MLIRLLVMDialect
MLIRInferIntRangeInterface
)