1 files changed, 71 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/floattisf.c b/compiler-rt/lib/builtins/floattisf.c
new file mode 100644
index 000000000000..a8fcdbe14c07
--- /dev/null
+++ b/compiler-rt/lib/builtins/floattisf.c
@@ -0,0 +1,71 @@
+//===-- floattisf.c - Implement __floattisf -------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements __floattisf for the compiler_rt library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "int_lib.h"
+
+#ifdef CRT_HAS_128BIT
+
+// Returns: convert a to a float, rounding toward even.
+
+// Assumption: float is a IEEE 32 bit floating point type
+//             ti_int is a 128 bit integral type
+
+// seee eeee emmm mmmm mmmm mmmm mmmm mmmm
+
+COMPILER_RT_ABI float __floattisf(ti_int a) {
+  if (a == 0)
+    return 0.0F;
+  const unsigned N = sizeof(ti_int) * CHAR_BIT;
+  const ti_int s = a >> (N - 1);
+  a = (a ^ s) - s;
+  int sd = N - __clzti2(a); // number of significant digits
+  int e = sd - 1;           // exponent
+  if (sd > FLT_MANT_DIG) {
+    //  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
+    // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
+    //                                                12345678901234567890123456
+    //  1 = msb 1 bit
+    //  P = bit FLT_MANT_DIG-1 bits to the right of 1
+    //  Q = bit FLT_MANT_DIG bits to the right of 1
+    //  R = "or" of all bits to the right of Q
+    switch (sd) {
+    case FLT_MANT_DIG + 1:
+      a <<= 1;
+      break;
+    case FLT_MANT_DIG + 2:
+      break;
+    default:
+      a = ((tu_int)a >> (sd - (FLT_MANT_DIG + 2))) |
+          ((a & ((tu_int)(-1) >> ((N + FLT_MANT_DIG + 2) - sd))) != 0);
+    };
+    // finish:
+    a |= (a & 4) != 0; // Or P into R
+    ++a;               // round - this step may add a significant bit
+    a >>= 2;           // dump Q and R
+    // a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits
+    if (a & ((tu_int)1 << FLT_MANT_DIG)) {
+      a >>= 1;
+      ++e;
+    }
+    // a is now rounded to FLT_MANT_DIG bits
+  } else {
+    a <<= (FLT_MANT_DIG - sd);
+    // a is now rounded to FLT_MANT_DIG bits
+  }
+  float_bits fb;
+  fb.u = ((su_int)s & 0x80000000) | // sign
+         ((e + 127) << 23) |        // exponent
+         ((su_int)a & 0x007FFFFF);  // mantissa
+  return fb.f;
+}
+
+#endif // CRT_HAS_128BIT