cmd/compile: implement global new(T) without calling newobject

[josharian]

package p

var x = new(int)

This generates init code to call newobject (including a write barrier, which I thought wasn't supposed to happen any more?). Instead, we should make a BSS int symbol, and then make x contain a relocation to that symbol.

cc @randall77 @mvdan

[randall77]

No, we still need a write barrier when initializing a global location.

The write barriers I changed recently removes them when initializing the contents of the results of a newobject call. Not sure if you're referring to that.

Yes, we can and should allocate the int statically. Small caveat: watch out for #29068.

[Skarlso]

Hi @josharian! Can I help?

[josharian]

Go for it. You'll be looking at sinit.go. It's not particularly clear code, even by compiler standards. I recommend writing yourself a few simplified examples to work off of.

[Skarlso]

Sounds lovely. :D But at least I'll learn while trying to figure it out. Which is always good. :)

[Skarlso]

Picking this up now. Sorry, was pre-occupied with another issue on packages. :)