cmd/compile: don’t consider recursive calls for inlining

We will never inline recursive calls.
Rather than simulate the recursion until we hit
the complexity ceiling, just bail early.

Also, remove a pointless n.Op check.
visitBottomUp guarantees that n will be an
ODCLFUNC, and caninl double-checks it.

Change-Id: Ifa48331686b24289d34e68cf5bef385f464b6b92
Reviewed-on: https://go-review.googlesource.com/27462
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/compile/internal/gc/main.go

@@ -438,10 +438,10 @@ func Main() {
 		// Find functions that can be inlined and clone them before walk expands them.
 		visitBottomUp(xtop, func(list []*Node, recursive bool) {
 			for _, n := range list {
-				if n.Op == ODCLFUNC {
+				if !recursive {
 					caninl(n)
-					inlcalls(n)
 				}
+				inlcalls(n)
 			}
 		})
 	}