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Fix Noise compiled under clang >= 3.7.x with -O2 or higher
When compiled with optimizations, the most recent versions of clang seem to 'optimize' out a crucial "and %reg, 0x7FFFFFFF" instruction in noise2d(), probably because it somehow assumed the variable n would never become greater than that amount. Indeed, signed integer underflow is undefined behavior in C and C++, so while this optimization is "correct" in that sense, it breaks lots of existing code. Solved by changing n to an unsigned type, making behavior well-defined.
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@ -158,21 +158,21 @@ s32 PcgRandom::randNormalDist(s32 min, s32 max, int num_trials)
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float noise2d(int x, int y, int seed)
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{
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int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y
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unsigned int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y
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+ NOISE_MAGIC_SEED * seed) & 0x7fffffff;
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n = (n >> 13) ^ n;
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n = (n * (n * n * 60493 + 19990303) + 1376312589) & 0x7fffffff;
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return 1.f - (float)n / 0x40000000;
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return 1.f - (float)(int)n / 0x40000000;
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}
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float noise3d(int x, int y, int z, int seed)
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{
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int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y + NOISE_MAGIC_Z * z
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unsigned int n = (NOISE_MAGIC_X * x + NOISE_MAGIC_Y * y + NOISE_MAGIC_Z * z
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+ NOISE_MAGIC_SEED * seed) & 0x7fffffff;
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n = (n >> 13) ^ n;
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n = (n * (n * n * 60493 + 19990303) + 1376312589) & 0x7fffffff;
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return 1.f - (float)n / 0x40000000;
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return 1.f - (float)(int)n / 0x40000000;
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}
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