Performance optimization SSE vector dot/normalize

lipsryme · 2013-10-10T07:59:01

Hey guys, I've done a "quick" first implementation of a vector normalize and dot product using sse intrinsics and was wondering if there's still something that could be optimized further. Here's my code: _declspec(align(16)) struct Vec4 { float x, y, z, w; inline const Vec4 Normalize() { __m128 tmp; // copy data into the 128bit register tmp = _mm_set_ps(w, z, y, x); // 0x7F = 0111 1111 ~ means we don't want the w-component multiplied // and the result written to all 4 components __m128 dp = _mm_dp_ps(tmp, tmp, 0x7F); // compute rsqrt of the dot product dp = _mm_rsqrt_ps(dp); // vec * rsqrt(dot(vec, vec)) tmp = _mm_mul_ps(tmp, dp); Vec4 vec; union {__m128 v; float f[4]; } uf; // to access the 4 floats uf.v = tmp; vec.x = uf.f[0]; vec.y = uf.f[1]; vec.z = uf.f[2]; vec.w = 1.0f; return vec; } inline const float Dot(const Vec4 &v2) { __m128 a; // copy data into the 128bit register a = _mm_set_ps(w, z, y, x); __m128 b = _mm_set_ps(v2.w, v2.z, v2.y, v2.x); // 0x7F = 0111 1111 ~ means we don't want w-component multiplied // and the result written to all 4 components __m128 dp = _mm_dp_ps(a, b, 0x7F); Vec4 vec; union {__m128 v; float f[4]; } uf; // to access the 4 floats uf.v = dp; return uf.f[0]; } }; Thanks in advance

Math and Physics Programming

Started by lipsryme September 20, 2013 03:26 PM

19 comments, last by Vilem Otte 10 years, 6 months ago

Vilem Otte

3,376

October 10, 2013 07:59 AM

MSVC is horribly bad with vectorized code, even 2012 isn't as good as F.e. GCC or ICC are. Sadly as you are forced to MSVC 2008 you can either use inline assembly, or just live with horribly bad vectorized code.

My current blog on programming, linux and stuff - http://gameprogrammerdiary.blogspot.com

Performance optimization SSE vector dot/normalize

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Performance optimization SSE vector dot/normalize

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