From d04db955fe27df768014ecc8146d94dfc274d3bb Mon Sep 17 00:00:00 2001
From: yutotnh <57719497+yutotnh@users.noreply.github.com>
Date: Mon, 7 Aug 2023 21:19:55 +0900
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---
 src/spirit/src/bfloat16.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/spirit/src/bfloat16.cpp b/src/spirit/src/bfloat16.cpp
index d025cc1..9ddbc70 100644
--- a/src/spirit/src/bfloat16.cpp
+++ b/src/spirit/src/bfloat16.cpp
@@ -25,8 +25,10 @@ float bfloat16_to_float32(const uint16_t bfloat16)
             return std::numeric_limits<float>::quiet_NaN() * sign;
         }
     } else {
-        constexpr uint32_t exponent_bias = 127 + 7;  // 128: 指数部の0x7Fのオフセット, 7: 仮数部のビット数
-        return std::ldexp(static_cast<float>(mantissa) + 128.0F, exponent - exponent_bias) * sign;
+        constexpr uint32_t exponent_bias = 127 + 7;  // 127: 指数部の0x7Fのオフセット, 7: 仮数部のビット数
+        const uint32_t actual_mantissa = mantissa + 128;  // ケチ表現で省略された最上位ビットを復元
+
+        return std::ldexp(actual_mantissa, exponent - exponent_bias) * sign;
     }
 }