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-rw-r--r--libc/src/math/generic/sin.cpp129
1 files changed, 57 insertions, 72 deletions
diff --git a/libc/src/math/generic/sin.cpp b/libc/src/math/generic/sin.cpp
index da3d1e94b5f6..2e1d3ffd5f37 100644
--- a/libc/src/math/generic/sin.cpp
+++ b/libc/src/math/generic/sin.cpp
@@ -18,17 +18,14 @@
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
#include "src/__support/macros/properties/cpu_features.h" // LIBC_TARGET_CPU_HAS_FMA
+#include "src/math/generic/range_reduction_double_common.h"
#include "src/math/generic/sincos_eval.h"
-// TODO: We might be able to improve the performance of large range reduction of
-// non-FMA targets further by operating directly on 25-bit chunks of 128/pi and
-// pre-split SIN_K_PI_OVER_128, but that might double the memory footprint of
-// those lookup table.
-#include "range_reduction_double_common.h"
-
-#if ((LIBC_MATH & LIBC_MATH_SKIP_ACCURATE_PASS) != 0)
-#define LIBC_MATH_SIN_SKIP_ACCURATE_PASS
-#endif
+#ifdef LIBC_TARGET_CPU_HAS_FMA
+#include "range_reduction_double_fma.h"
+#else
+#include "range_reduction_double_nofma.h"
+#endif // LIBC_TARGET_CPU_HAS_FMA
namespace LIBC_NAMESPACE_DECL {
@@ -43,33 +40,39 @@ LLVM_LIBC_FUNCTION(double, sin, (double x)) {
DoubleDouble y;
unsigned k;
- generic::LargeRangeReduction<NO_FMA> range_reduction_large{};
+ LargeRangeReduction range_reduction_large{};
- // |x| < 2^32 (with FMA) or |x| < 2^23 (w/o FMA)
+ // |x| < 2^16
if (LIBC_LIKELY(x_e < FPBits::EXP_BIAS + FAST_PASS_EXPONENT)) {
- // |x| < 2^-26
- if (LIBC_UNLIKELY(x_e < FPBits::EXP_BIAS - 26)) {
- // Signed zeros.
- if (LIBC_UNLIKELY(x == 0.0))
- return x;
+ // |x| < 2^-7
+ if (LIBC_UNLIKELY(x_e < FPBits::EXP_BIAS - 7)) {
+ // |x| < 2^-26, |sin(x) - x| < ulp(x)/2.
+ if (LIBC_UNLIKELY(x_e < FPBits::EXP_BIAS - 26)) {
+ // Signed zeros.
+ if (LIBC_UNLIKELY(x == 0.0))
+ return x;
- // For |x| < 2^-26, |sin(x) - x| < ulp(x)/2.
#ifdef LIBC_TARGET_CPU_HAS_FMA
- return fputil::multiply_add(x, -0x1.0p-54, x);
+ return fputil::multiply_add(x, -0x1.0p-54, x);
#else
- if (LIBC_UNLIKELY(x_e < 4)) {
- int rounding_mode = fputil::quick_get_round();
- if (rounding_mode == FE_TOWARDZERO ||
- (xbits.sign() == Sign::POS && rounding_mode == FE_DOWNWARD) ||
- (xbits.sign() == Sign::NEG && rounding_mode == FE_UPWARD))
- return FPBits(xbits.uintval() - 1).get_val();
- }
- return fputil::multiply_add(x, -0x1.0p-54, x);
+ if (LIBC_UNLIKELY(x_e < 4)) {
+ int rounding_mode = fputil::quick_get_round();
+ if (rounding_mode == FE_TOWARDZERO ||
+ (xbits.sign() == Sign::POS && rounding_mode == FE_DOWNWARD) ||
+ (xbits.sign() == Sign::NEG && rounding_mode == FE_UPWARD))
+ return FPBits(xbits.uintval() - 1).get_val();
+ }
+ return fputil::multiply_add(x, -0x1.0p-54, x);
#endif // LIBC_TARGET_CPU_HAS_FMA
+ }
+ // No range reduction needed.
+ k = 0;
+ y.lo = 0.0;
+ y.hi = x;
+ } else {
+ // Small range reduction.
+ k = range_reduction_small(x, y);
}
-
- // // Small range reduction.
- k = range_reduction_small(x, y);
} else {
// Inf or NaN
if (LIBC_UNLIKELY(x_e > 2 * FPBits::EXP_BIAS)) {
@@ -82,69 +85,51 @@ LLVM_LIBC_FUNCTION(double, sin, (double x)) {
}
// Large range reduction.
- k = range_reduction_large.compute_high_part(x);
- y = range_reduction_large.fast();
+ k = range_reduction_large.fast(x, y);
}
DoubleDouble sin_y, cos_y;
- generic::sincos_eval(y, sin_y, cos_y);
+ [[maybe_unused]] double err = generic::sincos_eval(y, sin_y, cos_y);
// Look up sin(k * pi/128) and cos(k * pi/128)
- // Memory saving versions:
-
- // Use 128-entry table instead:
- // DoubleDouble sin_k = SIN_K_PI_OVER_128[k & 127];
- // uint64_t sin_s = static_cast<uint64_t>(k & 128) << (63 - 7);
- // sin_k.hi = FPBits(FPBits(sin_k.hi).uintval() ^ sin_s).get_val();
- // sin_k.lo = FPBits(FPBits(sin_k.hi).uintval() ^ sin_s).get_val();
- // DoubleDouble cos_k = SIN_K_PI_OVER_128[(k + 64) & 127];
- // uint64_t cos_s = static_cast<uint64_t>((k + 64) & 128) << (63 - 7);
- // cos_k.hi = FPBits(FPBits(cos_k.hi).uintval() ^ cos_s).get_val();
- // cos_k.lo = FPBits(FPBits(cos_k.hi).uintval() ^ cos_s).get_val();
-
- // Use 64-entry table instead:
- // auto get_idx_dd = [](unsigned kk) -> DoubleDouble {
- // unsigned idx = (kk & 64) ? 64 - (kk & 63) : (kk & 63);
- // DoubleDouble ans = SIN_K_PI_OVER_128[idx];
- // if (kk & 128) {
- // ans.hi = -ans.hi;
- // ans.lo = -ans.lo;
- // }
- // return ans;
- // };
- // DoubleDouble sin_k = get_idx_dd(k);
- // DoubleDouble cos_k = get_idx_dd(k + 64);
-
+#ifdef LIBC_MATH_HAS_SMALL_TABLES
+ // Memory saving versions. Use 65-entry table.
+ auto get_idx_dd = [](unsigned kk) -> DoubleDouble {
+ unsigned idx = (kk & 64) ? 64 - (kk & 63) : (kk & 63);
+ DoubleDouble ans = SIN_K_PI_OVER_128[idx];
+ if (kk & 128) {
+ ans.hi = -ans.hi;
+ ans.lo = -ans.lo;
+ }
+ return ans;
+ };
+ DoubleDouble sin_k = get_idx_dd(k);
+ DoubleDouble cos_k = get_idx_dd(k + 64);
+#else
// Fast look up version, but needs 256-entry table.
// cos(k * pi/128) = sin(k * pi/128 + pi/2) = sin((k + 64) * pi/128).
DoubleDouble sin_k = SIN_K_PI_OVER_128[k & 255];
DoubleDouble cos_k = SIN_K_PI_OVER_128[(k + 64) & 255];
+#endif
// After range reduction, k = round(x * 128 / pi) and y = x - k * (pi / 128).
// So k is an integer and -pi / 256 <= y <= pi / 256.
// Then sin(x) = sin((k * pi/128 + y)
// = sin(y) * cos(k*pi/128) + cos(y) * sin(k*pi/128)
- DoubleDouble sin_k_cos_y = fputil::quick_mult<NO_FMA>(cos_y, sin_k);
- DoubleDouble cos_k_sin_y = fputil::quick_mult<NO_FMA>(sin_y, cos_k);
+ DoubleDouble sin_k_cos_y = fputil::quick_mult(cos_y, sin_k);
+ DoubleDouble cos_k_sin_y = fputil::quick_mult(sin_y, cos_k);
DoubleDouble rr = fputil::exact_add<false>(sin_k_cos_y.hi, cos_k_sin_y.hi);
rr.lo += sin_k_cos_y.lo + cos_k_sin_y.lo;
-#ifdef LIBC_MATH_SIN_SKIP_ACCURATE_PASS
+#ifdef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
return rr.hi + rr.lo;
#else
// Accurate test and pass for correctly rounded implementation.
-#ifdef LIBC_TARGET_CPU_HAS_FMA
- constexpr double ERR = 0x1.0p-70;
-#else
- // TODO: Improve non-FMA fast pass accuracy.
- constexpr double ERR = 0x1.0p-66;
-#endif // LIBC_TARGET_CPU_HAS_FMA
-
- double rlp = rr.lo + ERR;
- double rlm = rr.lo - ERR;
+ double rlp = rr.lo + err;
+ double rlm = rr.lo - err;
double r_upper = rr.hi + rlp; // (rr.lo + ERR);
double r_lower = rr.hi + rlm; // (rr.lo - ERR);
@@ -155,7 +140,7 @@ LLVM_LIBC_FUNCTION(double, sin, (double x)) {
Float128 u_f128, sin_u, cos_u;
if (LIBC_LIKELY(x_e < FPBits::EXP_BIAS + FAST_PASS_EXPONENT))
- u_f128 = generic::range_reduction_small_f128(x);
+ u_f128 = range_reduction_small_f128(x);
else
u_f128 = range_reduction_large.accurate();
@@ -163,7 +148,7 @@ LLVM_LIBC_FUNCTION(double, sin, (double x)) {
auto get_sin_k = [](unsigned kk) -> Float128 {
unsigned idx = (kk & 64) ? 64 - (kk & 63) : (kk & 63);
- Float128 ans = generic::SIN_K_PI_OVER_128_F128[idx];
+ Float128 ans = SIN_K_PI_OVER_128_F128[idx];
if (kk & 128)
ans.sign = Sign::NEG;
return ans;
@@ -182,7 +167,7 @@ LLVM_LIBC_FUNCTION(double, sin, (double x)) {
// https://github.com/llvm/llvm-project/issues/96452.
return static_cast<double>(r);
-#endif // !LIBC_MATH_SIN_SKIP_ACCURATE_PASS
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
}
} // namespace LIBC_NAMESPACE_DECL
generated by cgit v1.2.3 (git 2.25.1) at 2026-05-31 10:02:45 +0000