diff options
| -rw-r--r-- | target/ppc/fpu_helper.c | 17 |
1 files changed, 13 insertions, 4 deletions
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c index 52bcda27a6..07bc9051b0 100644 --- a/target/ppc/fpu_helper.c +++ b/target/ppc/fpu_helper.c @@ -73,11 +73,20 @@ uint64_t helper_todouble(uint32_t arg) /* Zero or Denormalized operand. */ ret = (uint64_t)extract32(arg, 31, 1) << 63; if (unlikely(abs_arg != 0)) { - /* Denormalized operand. */ - int shift = clz32(abs_arg) - 9; - int exp = -126 - shift + 1023; + /* + * Denormalized operand. + * Shift fraction so that the msb is in the implicit bit position. + * Thus, shift is in the range [1:23]. + */ + int shift = clz32(abs_arg) - 8; + /* + * The first 3 terms compute the float64 exponent. We then bias + * this result by -1 so that we can swallow the implicit bit below. + */ + int exp = -126 - shift + 1023 - 1; + ret |= (uint64_t)exp << 52; - ret |= abs_arg << (shift + 29); + ret += (uint64_t)abs_arg << (52 - 23 + shift); } } return ret; |