[skybrian]

It's certainly surprising, particularly since Go has its own extensive test suites and quite a few people have used the prereleases (including being deployed within Google and running all those tests as well).

It suggests the error is somehow not that commonly triggered in a visible way, or lots of tests would have broken. Or alternately it was a last-minute change.

[pcwalton]

Looks like a register allocation bug, which is the kind of thing that can only trigger in specific circumstances.

It looks like the Go compilers are especially vulnerable to this because individual AST nodes have to allocate registers, which would not be a problem if they used a more traditional IR.

[enneff]

There's work underway to implement the SSA form for amd64 in 1.6.