1 files changed, 94 insertions, 0 deletions
diff --git a/pl/math/v_expm1f_1u6.c b/pl/math/v_expm1f_1u6.c
new file mode 100644
index 0000000..ab13242
--- /dev/null
+++ b/pl/math/v_expm1f_1u6.c
@@ -0,0 +1,94 @@
+/*
+ * Single-precision vector exp(x) - 1 function.
+ *
+ * Copyright (c) 2022-2023, Arm Limited.
+ * SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
+ */
+
+#include "v_math.h"
+#include "pl_sig.h"
+#include "pl_test.h"
+
+#if V_SUPPORTED
+
+#define Shift v_f32 (0x1.8p23f)
+#define InvLn2 v_f32 (0x1.715476p+0f)
+#define MLn2hi v_f32 (-0x1.62e4p-1f)
+#define MLn2lo v_f32 (-0x1.7f7d1cp-20f)
+#define AbsMask (0x7fffffff)
+#define One (0x3f800000)
+#define SpecialBound                                                           \
+  (0x42af5e20) /* asuint(0x1.5ebc4p+6). Largest value of x for which expm1(x)  \
+		  should round to -1.  */
+#define TinyBound (0x34000000) /* asuint(0x1p-23).  */
+
+#define C(i) v_f32 (__expm1f_poly[i])
+
+/* Single-precision vector exp(x) - 1 function.
+   The maximum error is 1.51 ULP:
+   expm1f(0x1.8baa96p-2) got 0x1.e2fb9p-2
+			want 0x1.e2fb94p-2.  */
+VPCS_ATTR
+v_f32_t V_NAME (expm1f) (v_f32_t x)
+{
+  v_u32_t ix = v_as_u32_f32 (x);
+  v_u32_t ax = ix & AbsMask;
+
+#if WANT_SIMD_EXCEPT
+  /* If fp exceptions are to be triggered correctly, fall back to the scalar
+     variant for all lanes if any of them should trigger an exception.  */
+  v_u32_t special
+    = v_cond_u32 ((ax >= SpecialBound) | (ix == 0x80000000) | (ax < TinyBound));
+  if (unlikely (v_any_u32 (special)))
+    return v_call_f32 (expm1f, x, x, v_u32 (0xffffffff));
+#else
+  /* Handles very large values (+ve and -ve), +/-NaN, +/-Inf and -0.  */
+  v_u32_t special = v_cond_u32 ((ax >= SpecialBound) | (ix == 0x80000000));
+#endif
+
+  /* Reduce argument to smaller range:
+     Let i = round(x / ln2)
+     and f = x - i * ln2, then f is in [-ln2/2, ln2/2].
+     exp(x) - 1 = 2^i * (expm1(f) + 1) - 1
+     where 2^i is exact because i is an integer.  */
+  v_f32_t j = v_fma_f32 (InvLn2, x, Shift) - Shift;
+  v_s32_t i = v_to_s32_f32 (j);
+  v_f32_t f = v_fma_f32 (j, MLn2hi, x);
+  f = v_fma_f32 (j, MLn2lo, f);
+
+  /* Approximate expm1(f) using polynomial.
+     Taylor expansion for expm1(x) has the form:
+	 x + ax^2 + bx^3 + cx^4 ....
+     So we calculate the polynomial P(f) = a + bf + cf^2 + ...
+     and assemble the approximation expm1(f) ~= f + f^2 * P(f).  */
+
+  v_f32_t p = v_fma_f32 (C (4), f, C (3));
+  p = v_fma_f32 (p, f, C (2));
+  p = v_fma_f32 (p, f, C (1));
+  p = v_fma_f32 (p, f, C (0));
+  p = v_fma_f32 (f * f, p, f);
+
+  /* Assemble the result.
+     expm1(x) ~= 2^i * (p + 1) - 1
+     Let t = 2^i.  */
+  v_f32_t t = v_as_f32_u32 (v_as_u32_s32 (i << 23) + One);
+  /* expm1(x) ~= p * t + (t - 1).  */
+  v_f32_t y = v_fma_f32 (p, t, t - 1);
+
+#if !WANT_SIMD_EXCEPT
+  if (unlikely (v_any_u32 (special)))
+    return v_call_f32 (expm1f, x, y, special);
+#endif
+
+  return y;
+}
+VPCS_ALIAS
+
+PL_SIG (V, F, 1, expm1, -9.9, 9.9)
+PL_TEST_ULP (V_NAME (expm1f), 1.02)
+PL_TEST_EXPECT_FENV (V_NAME (expm1f), WANT_SIMD_EXCEPT)
+PL_TEST_INTERVAL (V_NAME (expm1f), 0, 0x1p-23, 1000)
+PL_TEST_INTERVAL (V_NAME (expm1f), -0, -0x1p-23, 1000)
+PL_TEST_INTERVAL (V_NAME (expm1f), 0x1p-23, 0x1.644716p6, 1000000)
+PL_TEST_INTERVAL (V_NAME (expm1f), -0x1p-23, -0x1.9bbabcp+6, 1000000)
+#endif