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[BugFix][Target][LLVM] Use libm for asin/acos instead of buggy inline Taylor #19567

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[BugFix][Target][LLVM] Use libm for asin/acos instead of buggy inline Taylor #19567

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aa19183
[BugFix][LLVM] Use libm for asin/acos instead of buggy inline Taylor
swjng May 15, 2026
9d9730d
[BugFix][Target][LLVM] Drop redundant NaN guard around libm asin/acos
swjng May 15, 2026
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47 changes: 2 additions & 45 deletions src/target/llvm/intrin_rule_llvm.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -173,61 +173,18 @@ TVM_REGISTER_OP("tirx.sinh")

TVM_REGISTER_OP("tirx.asin")
.set_attr<FLegalize>("llvm.FLegalize", [](const PrimExpr& e) -> PrimExpr {
using tirx::make_const;
using namespace intrin;
const tirx::CallNode* call = e.as<tirx::CallNode>();
TVM_FFI_ICHECK(call != nullptr);
const PrimExpr& x = call->args[0];

PrimExpr threshold = make_const(x.dtype(), 0.5);
PrimExpr abs_x = tvm::abs(x);
PrimExpr use_lib = abs_x >= threshold;

PrimExpr x2 = x * x;
PrimExpr term1 = x;
PrimExpr term3 = term1 * x2 / make_const(x.dtype(), 6);
PrimExpr term5 = term3 * x2 * make_const(x.dtype(), 9) / make_const(x.dtype(), 40);
PrimExpr term7 = term5 * x2 * make_const(x.dtype(), 25) / make_const(x.dtype(), 112);
PrimExpr term9 = term7 * x2 * make_const(x.dtype(), 1225) / make_const(x.dtype(), 3456);
PrimExpr term11 = term9 * x2 * make_const(x.dtype(), 3969) / make_const(x.dtype(), 28160);
PrimExpr series = term1 + term3 + term5 + term7 + term9 + term11;

PrimExpr lib_result =
::tvm::codegen::intrin::DispatchPureExtern<::tvm::codegen::intrin::FloatSuffix>(e);

PrimExpr lower = make_const(x.dtype(), -1.0);
PrimExpr upper = make_const(x.dtype(), 1.0);
PrimExpr out_range = tirx::Or(x<lower, x> upper);
PrimExpr nan_const = make_const(x.dtype(), std::numeric_limits<double>::quiet_NaN());

return tirx::Select(out_range, nan_const, tirx::Select(use_lib, lib_result, series));
return ::tvm::codegen::intrin::DispatchPureExtern<::tvm::codegen::intrin::FloatSuffix>(e);
});

TVM_REGISTER_OP("tirx.acos")
.set_attr<FLegalize>("llvm.FLegalize", [](const PrimExpr& e) -> PrimExpr {
using tirx::make_const;
using namespace intrin;
const tirx::CallNode* call = e.as<tirx::CallNode>();
TVM_FFI_ICHECK(call != nullptr) << "Invalid call node in acos legalization";
const PrimExpr& x = call->args[0];

PrimExpr threshold = make_const(x.dtype(), 0.5);
PrimExpr abs_x = tvm::abs(x);
PrimExpr use_lib = abs_x >= threshold;

PrimExpr half_pi = make_const(x.dtype(), M_PI / 2);
PrimExpr asin_x = asin(x);
PrimExpr formula_result = half_pi - asin_x;

PrimExpr lib_result =
::tvm::codegen::intrin::DispatchPureExtern<::tvm::codegen::intrin::FloatSuffix>(e);

PrimExpr lower = make_const(x.dtype(), -1.0);
PrimExpr upper = make_const(x.dtype(), 1.0);
PrimExpr out_range = tirx::Or(x<lower, x> upper);
PrimExpr nan_const = make_const(x.dtype(), std::numeric_limits<double>::quiet_NaN());

return tirx::Select(out_range, nan_const, tirx::Select(use_lib, lib_result, formula_result));
return ::tvm::codegen::intrin::DispatchPureExtern<::tvm::codegen::intrin::FloatSuffix>(e);
});

TVM_REGISTER_OP("tirx.atan")
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6 changes: 3 additions & 3 deletions tests/python/relax/test_frontend_onnx.py
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Original file line number Diff line number Diff line change
Expand Up @@ -705,9 +705,9 @@ def test_bitwise_shift(direction: str):
"Sinh",
"Cosh",
"Tanh",
# "Asin", // TODO @jikechao, fix the precision loss due to the Taylor approximation
# "Acos",
# "Atan",
"Asin",
"Acos",
# "Atan", // TODO: fix x²+1 overflow in llvm legalize for huge inputs (issue #19560)
"Asinh",
"Acosh",
"Atanh",
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