Go Build Constraints Optimize implementations based on architecture
Example
We can optimize a simple xor function for only architectures that support unaligned reads/writes by creating two files that define the function and prefixing them with a build constraint (for an actual example of the xor code which is out of scope here, see crypto/cipher/xor.go in the standard library):
// +build 386 amd64 s390x
package cipher
func xorBytes(dst, a, b []byte) int { /* This function uses unaligned reads / writes to optimize the operation */ }
and for other architectures:
// +build !386,!amd64,!s390x
package cipher
func xorBytes(dst, a, b []byte) int { /* This version of the function just loops and xors */ }
