1 files changed, 106 insertions, 0 deletions
diff --git a/lib/libcompiler_rt/ppc/fixunstfti.c b/lib/libcompiler_rt/ppc/fixunstfti.c
new file mode 100644
index 00000000000..fa21084cb57
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+++ b/lib/libcompiler_rt/ppc/fixunstfti.c
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+//===-- lib/builtins/ppc/fixunstfti.c - Convert long double->int128 *-C -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements converting the 128bit IBM/PowerPC long double (double-
+// double) data type to an unsigned 128 bit integer.
+//
+//===----------------------------------------------------------------------===//
+
+#include "../int_math.h"
+#define BIAS 1023
+
+/* Convert long double into an unsigned 128-bit integer. */
+__uint128_t __fixunstfti(long double input) {
+
+  /* If we are trying to convert a NaN, return the NaN bit pattern. */
+  if (crt_isnan(input)) {
+    return ((__uint128_t)0x7FF8000000000000ll) << 64 |
+           (__uint128_t)0x0000000000000000ll;
+  }
+
+  __uint128_t result, hiResult, loResult;
+  int hiExponent, loExponent, shift;
+  /* The long double representation, with the high and low portions of
+   * the long double, and the corresponding bit patterns of each double. */
+  union {
+    long double ld;
+    double d[2]; /* [0] is the high double, [1] is the low double. */
+    unsigned long long ull[2]; /* High and low doubles as 64-bit integers. */
+  } ldUnion;
+
+  /* If the long double is less than 1.0 or negative,
+   * return 0.0. */
+  if (input < 1.0)
+    return 0.0;
+
+  /* Retrieve the 64-bit patterns of high and low doubles.
+   * Compute the unbiased exponent of both high and low doubles by
+   * removing the signs, isolating the exponent, and subtracting
+   * the bias from it. */
+  ldUnion.ld = input;
+  hiExponent = ((ldUnion.ull[0] & 0x7FFFFFFFFFFFFFFFll) >> 52) - BIAS;
+  loExponent = ((ldUnion.ull[1] & 0x7FFFFFFFFFFFFFFFll) >> 52) - BIAS;
+
+  /* Convert each double into int64; they will be added to the int128 result.
+   * CASE 1: High or low double fits in int64
+   *      - Convert the each double normally into int64.
+   *
+   * CASE 2: High or low double does not fit in int64
+   *      - Scale the double to fit within a 64-bit integer
+   *      - Calculate the shift (amount to scale the double by in the int128)
+   *      - Clear all the bits of the exponent (with 0x800FFFFFFFFFFFFF)
+   *      - Add BIAS+53 (0x4350000000000000) to exponent to correct the value
+   *      - Scale (move) the double to the correct place in the int128
+   *        (Move it by 2^53 places)
+   *
+   * Note: If the high double is assumed to be positive, an unsigned conversion
+   * from long double to 64-bit integer is needed. The low double can be either
+   * positive or negative, so a signed conversion is needed to retain the result
+   * of the low double and to ensure it does not simply get converted to 0. */
+
+  /* CASE 1 - High double fits in int64. */
+  if (hiExponent < 63) {
+    hiResult = (unsigned long long)ldUnion.d[0];
+  } else if (hiExponent < 128) {
+    /* CASE 2 - High double does not fit in int64, scale and convert it. */
+    shift = hiExponent - 54;
+    ldUnion.ull[0] &= 0x800FFFFFFFFFFFFFll;
+    ldUnion.ull[0] |= 0x4350000000000000ll;
+    hiResult = (unsigned long long)ldUnion.d[0];
+    hiResult <<= shift;
+  } else {
+    /* Detect cases for overflow. When the exponent of the high
+     * double is greater than 128 bits and when the long double
+     * input is positive, return the max 128-bit integer.
+     * For negative inputs with exponents > 128, return 1, like gcc. */
+    if (ldUnion.d[0] > 0) {
+      return ((__uint128_t)0xFFFFFFFFFFFFFFFFll) << 64 |
+             (__uint128_t)0xFFFFFFFFFFFFFFFFll;
+    } else {
+      return ((__uint128_t)0x0000000000000000ll) << 64 |
+             (__uint128_t)0x0000000000000001ll;
+    }
+  }
+
+  /* CASE 1 - Low double fits in int64. */
+  if (loExponent < 63) {
+    loResult = (long long)ldUnion.d[1];
+  } else {
+    /* CASE 2 - Low double does not fit in int64, scale and convert it. */
+    shift = loExponent - 54;
+    ldUnion.ull[1] &= 0x800FFFFFFFFFFFFFll;
+    ldUnion.ull[1] |= 0x4350000000000000ll;
+    loResult = (long long)ldUnion.d[1];
+    loResult <<= shift;
+  }
+
+  /* Add the high and low doublewords together to form a 128 bit integer. */
+  result = loResult + hiResult;
+  return result;
+}