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author | Szabolcs Nagy <nsz@port70.net> | 2012-11-13 10:55:35 +0100 |
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committer | Szabolcs Nagy <nsz@port70.net> | 2012-11-13 10:55:35 +0100 |
commit | c4359e01303da2755fe7e8033826b132eb3659b1 (patch) | |
tree | 93cdddff4278c4f0b092ed001f235051a1cd1a72 /src/math/scalbnf.c | |
parent | 666271c105e4137bdfa195e217799d74143370d4 (diff) | |
download | musl-c4359e01303da2755fe7e8033826b132eb3659b1.tar.gz musl-c4359e01303da2755fe7e8033826b132eb3659b1.tar.xz musl-c4359e01303da2755fe7e8033826b132eb3659b1.zip |
math: excess precision fix modf, modff, scalbn, scalbnf
old code was correct only if the result was stored (without the excess precision) or musl was compiled with -ffloat-store. now we use STRICT_ASSIGN to work around the issue. (see note 160 in c11 section 6.8.6.4)
Diffstat (limited to 'src/math/scalbnf.c')
-rw-r--r-- | src/math/scalbnf.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/src/math/scalbnf.c b/src/math/scalbnf.c index e5c76db3..f94b5d59 100644 --- a/src/math/scalbnf.c +++ b/src/math/scalbnf.c @@ -2,8 +2,6 @@ float scalbnf(float x, int n) { - /* make sure result is stored as double on overflow or underflow */ - volatile float z; float scale; if (n > 127) { @@ -13,8 +11,8 @@ float scalbnf(float x, int n) x *= 0x1p127f; n -= 127; if (n > 127) { - z = x * 0x1p127f; - return z; + STRICT_ASSIGN(float, x, x * 0x1p127f); + return x; } } } else if (n < -126) { @@ -24,12 +22,12 @@ float scalbnf(float x, int n) x *= 0x1p-126f; n += 126; if (n < -126) { - z = x * 0x1p-126f; - return z; + STRICT_ASSIGN(float, x, x * 0x1p-126f); + return x; } } } SET_FLOAT_WORD(scale, (uint32_t)(0x7f+n)<<23); - z = x * scale; - return z; + STRICT_ASSIGN(float, x, x * scale); + return x; } |