changed 0.0 to 0x0.0p0, fixed MPFRUtils computation of mpfr_sinpi(x) for mpfr versions < 4.2

Author: wldfngrs

libc/src/math/generic/sinpif16.cpp

@@ -21,72 +21,25 @@ namespace LIBC_NAMESPACE_DECL {
 // Table is generated with Sollya as follows:
 // > display = hexadecimmal;
 // > for k from 0 to 63 do { round(sin(k * pi/32), SG, RN); };
-const float SIN_K_PI_OVER_32[64] = {0,
-                                    0x1.917a6cp-4,
-                                    0x1.8f8b84p-3,
-                                    0x1.294062p-2,
-                                    0x1.87de2ap-2,
-                                    0x1.e2b5d4p-2,
-                                    0x1.1c73b4p-1,
-                                    0x1.44cf32p-1,
-                                    0x1.6a09e6p-1,
-                                    0x1.8bc806p-1,
-                                    0x1.a9b662p-1,
-                                    0x1.c38b3p-1,
-                                    0x1.d906bcp-1,
-                                    0x1.e9f416p-1,
-                                    0x1.f6297cp-1,
-                                    0x1.fd88dap-1,
-                                    0x1p0,
-                                    0x1.fd88dap-1,
-                                    0x1.f6297cp-1,
-                                    0x1.e9f416p-1,
-                                    0x1.d906bcp-1,
-                                    0x1.c38b3p-1,
-                                    0x1.a9b662p-1,
-                                    0x1.8bc806p-1,
-                                    0x1.6a09e6p-1,
-                                    0x1.44cf32p-1,
-                                    0x1.1c73b4p-1,
-                                    0x1.e2b5d4p-2,
-                                    0x1.87de2ap-2,
-                                    0x1.294062p-2,
-                                    0x1.8f8b84p-3,
-                                    0x1.917a6cp-4,
-                                    0,
-                                    -0x1.917a6cp-4,
-                                    -0x1.8f8b84p-3,
-                                    -0x1.294062p-2,
-                                    -0x1.87de2ap-2,
-                                    -0x1.e2b5d4p-2,
-                                    -0x1.1c73b4p-1,
-                                    -0x1.44cf32p-1,
-                                    -0x1.6a09e6p-1,
-                                    -0x1.8bc806p-1,
-                                    -0x1.a9b662p-1,
-                                    -0x1.c38b3p-1,
-                                    -0x1.d906bcp-1,
-                                    -0x1.e9f416p-1,
-                                    -0x1.f6297ep-1,
-                                    -0x1.fd88dap-1,
-                                    -0x1p0,
-                                    -0x1.fd88dap-1,
-                                    -0x1.f6297cp-1,
-                                    -0x1.e9f416p-1,
-                                    -0x1.d906bcp-1,
-                                    -0x1.c38b3p-1,
-                                    -0x1.a9b662p-1,
-                                    -0x1.8bc806p-1,
-                                    -0x1.6a09e6p-1,
-                                    -0x1.44cf32p-1,
-                                    -0x1.1c73b4p-1,
-                                    -0x1.e2b5d4p-2,
-                                    -0x1.87de2ap-2,
-                                    -0x1.294062p-2,
-                                    -0x1.8f8b84p-3,
-                                    -0x1.917a6cp-4};
-
-int32_t range_reduction(float x, float &y) {
+static constexpr float SIN_K_PI_OVER_32[64] = {
+    0x0.0p0,        0x1.917a6cp-4,  0x1.8f8b84p-3,  0x1.294062p-2,
+    0x1.87de2ap-2,  0x1.e2b5d4p-2,  0x1.1c73b4p-1,  0x1.44cf32p-1,
+    0x1.6a09e6p-1,  0x1.8bc806p-1,  0x1.a9b662p-1,  0x1.c38b3p-1,
+    0x1.d906bcp-1,  0x1.e9f416p-1,  0x1.f6297cp-1,  0x1.fd88dap-1,
+    0x1p0,          0x1.fd88dap-1,  0x1.f6297cp-1,  0x1.e9f416p-1,
+    0x1.d906bcp-1,  0x1.c38b3p-1,   0x1.a9b662p-1,  0x1.8bc806p-1,
+    0x1.6a09e6p-1,  0x1.44cf32p-1,  0x1.1c73b4p-1,  0x1.e2b5d4p-2,
+    0x1.87de2ap-2,  0x1.294062p-2,  0x1.8f8b84p-3,  0x1.917a6cp-4,
+    0x0.0p0,        -0x1.917a6cp-4, -0x1.8f8b84p-3, -0x1.294062p-2,
+    -0x1.87de2ap-2, -0x1.e2b5d4p-2, -0x1.1c73b4p-1, -0x1.44cf32p-1,
+    -0x1.6a09e6p-1, -0x1.8bc806p-1, -0x1.a9b662p-1, -0x1.c38b3p-1,
+    -0x1.d906bcp-1, -0x1.e9f416p-1, -0x1.f6297ep-1, -0x1.fd88dap-1,
+    -0x1p0,         -0x1.fd88dap-1, -0x1.f6297cp-1, -0x1.e9f416p-1,
+    -0x1.d906bcp-1, -0x1.c38b3p-1,  -0x1.a9b662p-1, -0x1.8bc806p-1,
+    -0x1.6a09e6p-1, -0x1.44cf32p-1, -0x1.1c73b4p-1, -0x1.e2b5d4p-2,
+    -0x1.87de2ap-2, -0x1.294062p-2, -0x1.8f8b84p-3, -0x1.917a6cp-4};
+
+static LIBC_INLINE int32_t range_reduction(float x, float &y) {
   float kf = fputil::nearest_integer(x * 32);
   y = fputil::multiply_add<float>(x, 32.0, -kf);
 

libc/utils/MPFRWrapper/MPFRUtils.cpp

@@ -492,7 +492,19 @@ class MPFRNumber {
     MPFRNumber value_pi(0.0, 1280);
     mpfr_const_pi(value_pi.value, MPFR_RNDN);
     mpfr_mul(value_pi.value, value_pi.value, value, MPFR_RNDN);
-    mpfr_sin(result.value, value_pi.value, mpfr_rounding);
+
+    int ret = mpfr_integer_p(value);
+    MPFRNumber value_mul_two(*this);
+    mpfr_mul_si(value_mul_two.value, value, 2, MPFR_RNDN);
+    if (mpfr_integer_p(value_mul_two.value) != 0) {
+      if (ret != 0) {
+        mpfr_set_si(result.value, 0, mpfr_rounding);
+      } else {
+        mpfr_sin(result.value, value_pi.value, MPFR_RNDN);
+      }
+    } else {
+      mpfr_sin(result.value, value_pi.value, mpfr_rounding);
+    }
 #endif
 
     return result;