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Fix strict aliasing in gb_quake_inv_sqrt

This commit is contained in:
gingerBill 2016-04-08 23:05:38 +01:00
parent 386f6371d7
commit f2ee608bd5
1 changed files with 12 additions and 10 deletions
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22
gb_math.h
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@ -1,9 +1,10 @@
// gb_math.h - v0.04a - public domain C math library - no warranty implied; use at your own risk
// gb_math.h - v0.04b - public domain C math library - no warranty implied; use at your own risk
// A C math library geared towards game development
// use '#define GB_MATH_IMPLEMENTATION' before including to create the implementation in _ONE_ file
/*
Version History:
0.04b - Fix strict aliasing in gb_quake_inv_sqrt
0.04a - Minor bug fixes
0.04 - Namespace everything with gb
0.03 - Complete Replacement
@ -719,19 +720,20 @@ float gb_sqrt(float a) { return sqrtf(a); }
float
gb_quake_inv_sqrt(float a)
{
int i;
float x2, y;
union {
int i;
float f;
} t;
float x2;
float const three_halfs = 1.5f;
x2 = a * 0.5f;
y = a;
i = *(int *)&y; // Evil floating point bit level hacking
i = 0x5f375a86 - (i >> 1); // What the fuck?
y = *(float *)&i;
y = y * (three_halfs - (x2 * y * y)); // 1st iteration
y = y * (three_halfs - (x2 * y * y)); // 2nd iteration, this can be removed
t.f = a;
t.i = 0x5f375a86 - (t.i >> 1); // What the fuck?
t.f = t.f * (three_halfs - (x2 * t.f * t.f)); // 1st iteration
t.f = t.f * (three_halfs - (x2 * t.f * t.f)); // 2nd iteration, this can be removed
return y;
return t.f;
}
float gb_sin(float radians) { return sinf(radians); }