seadMathCalcCommonCafe.hpp

Go to the documentation of this file.

#pragma once
 
#ifndef DISABLE_PS
#include <ppc_ghs.h>
#endif
 
#include <basis/seadAssert.h>
 
namespace sead {
 
template <>
inline f32 MathCafe<f32>::rsqrt(f32 x)
{
    SEAD_ASSERT_MSG(x >= 0.0f, "x[%f] is out of the domain.", x);
 
    if (x <= 0.0f)
        return 0.0f;
 
    f32 v0;
    f32 v1;
    f32 v2;
    const f32 HALF  = 0.5f;
    const f32 THREE = 3.0f;
 
#ifdef SEAD_MATH_CAFE_RSQRT_USE_INTRINSICS
    // The use of inline assembly in an inline function can be very dangerous,
    // and sometimes triggers compiler bugs in GHS.
    // Therefore, use intrinsics instead.
    // (For use with custom applications)
    v0 = __FRSQRTE(x);
    v1 = v0 * v0;
    v2 = v0 * HALF;
    v1 = __FNMSUBS(v1, x, THREE);
    v0 = v1 * v2;
#else
    asm ("frsqrte %[v0], %[x]                 \n\t"
         "fmuls   %[v1], %[v0], %[v0]         \n\t"
         "fmuls   %[v2], %[v0], %[HALF]       \n\t"
         "fnmsubs %[v1], %[v1], %[x], %[THREE]\n\t"
         "fmuls   %[v0], %[v1], %[v2]             "
         : [v0] "=&f"(v0), [v1] "=&f"(v1), [   v2] "=&f"( v2)
         : [x]  "f"( x), [HALF] "f"(HALF), [THREE] "f"(THREE));
#endif
 
    return v0;
}
 
} // namespace sead