1 files changed, 57 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/ppc/fixunstfdi.c b/compiler-rt/lib/builtins/ppc/fixunstfdi.c
new file mode 100644
index 000000000000..8d53f372527a
--- /dev/null
+++ b/compiler-rt/lib/builtins/ppc/fixunstfdi.c
@@ -0,0 +1,57 @@
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// uint64_t __fixunstfdi(long double x);
+// This file implements the PowerPC 128-bit double-double -> uint64_t conversion
+
+#include "DD.h"
+
+uint64_t __fixunstfdi(long double input) {
+  const DD x = {.ld = input};
+  const doublebits hibits = {.d = x.s.hi};
+
+  const uint32_t highWordMinusOne =
+      (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000);
+
+  // If (1.0 - tiny) <= input < 0x1.0p64:
+  if (UINT32_C(0x04000000) > highWordMinusOne) {
+    const int unbiasedHeadExponent = highWordMinusOne >> 20;
+
+    uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); // mantissa(hi)
+    result |= UINT64_C(0x0010000000000000); // matissa(hi) with implicit bit
+    result <<= 11; // mantissa(hi) left aligned in the int64 field.
+
+    // If the tail is non-zero, we need to patch in the tail bits.
+    if (0.0 != x.s.lo) {
+      const doublebits lobits = {.d = x.s.lo};
+      int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
+      tailMantissa |= INT64_C(0x0010000000000000);
+
+      // At this point we have the mantissa of |tail|
+
+      const int64_t negationMask = ((int64_t)(lobits.x)) >> 63;
+      tailMantissa = (tailMantissa ^ negationMask) - negationMask;
+
+      // Now we have the mantissa of tail as a signed 2s-complement integer
+
+      const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
+
+      // Shift the tail mantissa into the right position, accounting for the
+      // bias of 11 that we shifted the head mantissa by.
+      tailMantissa >>=
+          (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11)));
+
+      result += tailMantissa;
+    }
+
+    result >>= (63 - unbiasedHeadExponent);
+    return result;
+  }
+
+  // Edge cases are handled here, with saturation.
+  if (1.0 > x.s.hi)
+    return UINT64_C(0);
+  else
+    return UINT64_MAX;
+}