Useful optimizations for retro game development on old hardware like: Nintendo GameCube, Wii, PS1, PS2, Dreamcast and embedded systems.

Retro C/C++ Optimization Guide

1. Division Using Multiplication

Floating-point division is expensive on old hardware. A common optimization is replacing division with multiplication using reciprocal values.

Division	Optimized Multiplication	Example
x / 2	x * 0.5f	value * 0.5f
x / 4	x * 0.25f	value * 0.25f
x / 8	x * 0.125f	value * 0.125f
x / 16	x * 0.0625f	value * 0.0625f
x / 32	x * 0.03125f	value * 0.03125f
x / 64	x * 0.015625f	value * 0.015625f

2. Integer Division Using Bit Shifts

Integer division by powers of two can be replaced with bit shifts. This is extremely fast on old CPUs.

Division	Bit Shift	Example
x / 2	x >> 1	value >> 1
x / 4	x >> 2	value >> 2
x / 8	x >> 3	value >> 3
x / 16	x >> 4	value >> 4
x / 32	x >> 5	value >> 5
x / 64	x >> 6	value >> 6

3. Example Code

// Floating point optimization
float half = value * 0.5f;

// Integer optimization
int halfInt = value >> 1;

// Vector normalization optimization
float invLength = fastInvSqrt(x*x + y*y);

x *= invLength;
y *= invLength;

4. Important Notes

• Bit shifts only work correctly for integer types.
• Multiplication by reciprocal values is useful for floating-point math.
• Modern compilers sometimes optimize divisions automatically.
• These optimizations are most useful in hot loops and math-heavy code.