cmd/compile: remove badgerbadgerbadger optimization?

[josharian]

From walk.go:

func walkcompareString(n *Node, init *Nodes) *Node {
	// s + "badgerbadgerbadger" == "badgerbadgerbadger"
	if (n.Op == OEQ || n.Op == ONE) && Isconst(n.Right, CTSTR) && n.Left.Op == OADDSTR && n.Left.List.Len() == 2 && Isconst(n.Left.List.Second(), CTSTR) && strlit(n.Right) == strlit(n.Left.List.Second()) {
		r := nod(n.Op, nod(OLEN, n.Left.List.First(), nil), nodintconst(0))
		return finishcompare(n, r, init)
	}

	// cont...

I've always been skeptical that anyone writes code that matches this pattern; I'd like to remove it.

Thoughts/objections?

cc @mdempsky @randall77

[randall77]

Fine by me. Might want to double-check that the stdlib doesn't have any (except a possible test for this optimization).

[mdempsky]

SGTM

[seebs]

That is a very common pattern... in bourne shell. Where the idiom is test "x$foo" != "x" as a workaround to handle cases where $foo might contain something that would be interpreted as a flag by the test command's option parser. I've also seen it in Makefiles, I think. I agree that it seems vanishingly unlikely to show up in go.

Also why is the function not called walkCompareString with a capital C?

[mdempsky]

Also why is the function not called walkCompareString with a capital C?

It's a subroutine of the vestigially-named walkcompare function. We try to toe a balance between adopting current Go conventions and staying consistent with the current archaic code base.

See also #27167.

[gopherbot]

Change https://golang.org/cl/163728 mentions this issue: cmd/compile: remove badgerbadgerbadger optimization

[rsc]

For the record, this was here because of https://groups.google.com/g/golang-nuts/c/7Ks1iq2s7FA/m/rS60bS4aMi4J.