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Interpeter: Fixed ConvertToDouble to match the manual.

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Also added some documntation comments.
This commit is contained in:
Scott Mansell 2014-02-06 20:44:42 +13:00 committed by Tillmann Karras
parent cf5938c4df
commit 7062cf8657
1 changed files with 16 additions and 11 deletions
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27
Source/Core/Core/PowerPC/Interpreter/Interpreter_FPUtils.h
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@ -234,24 +234,23 @@ inline u32 ConvertToSingleFTZ(u64 x)
inline u64 ConvertToDouble(u32 _x) inline u64 ConvertToDouble(u32 _x)
{ {
// This is a little-endian re-implementation of the algrothm described in
// the Power PC Programming Enviroments Manual for Loading single
// percision floating point numbers.
// See page 566 of http://www.freescale.com/files/product/doc/MPCFPE32B.pdf
u64 x = _x; u64 x = _x;
u64 exp = (x >> 23) & 0xff; u64 exp = (x >> 23) & 0xff;
u64 frac = x & 0x007fffff; u64 frac = x & 0x007fffff;
if (exp || frac == 0)
if (exp > 0 && exp < 255) // Normal number
{ {
// not denormalized u64 y = !(exp >> 7);
u64 y = exp & 0x80; u64 z = y << 61 | y << 60 | y << 59;
u64 z = y << 54 | y << 53 | y << 52;
if (exp > 0 && exp < 255)
{
// not inf/nan/zero
z = ~z;
}
return ((x & 0xc0000000) << 32) | z | ((x & 0x3fffffff) << 29); return ((x & 0xc0000000) << 32) | z | ((x & 0x3fffffff) << 29);
} }
else else if (exp == 0 && frac != 0) // Subnormal number
{ {
// denormalized
exp = 1023 - 126; exp = 1023 - 126;
do do
{ {
@ -260,4 +259,10 @@ inline u64 ConvertToDouble(u32 _x)
} while ((frac & 0x00800000) == 0); } while ((frac & 0x00800000) == 0);
return ((x & 0x80000000) << 32) | (exp << 52) | ((frac & 0x007fffff) << 29); return ((x & 0x80000000) << 32) | (exp << 52) | ((frac & 0x007fffff) << 29);
} }
else // QNaN, SNaN or Zero
{
u64 y = exp >> 7;
u64 z = y << 61 | y << 60 | y << 59;
return ((x & 0xc0000000) << 32) | z | ((x & 0x3fffffff) << 29);
}
} }