cmd/compile: change export.go and fmt.go to use nodeSeq

Also fix some uses of nodeSeqIterator.Len, and fix the implementation in
nodesIterator.

Passes toolstash -cmp.

Update #14473.

Change-Id: I228871470234b7f1314ffd2aae8a4c0624c35f98
Reviewed-on: https://go-review.googlesource.com/20231
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 615ec6e..2c7cb10 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -89,9 +89,9 @@
 	printssa := name == os.Getenv("GOSSAFUNC")
 	if printssa {
 		fmt.Println("generating SSA for", name)
-		dumpslice("buildssa-enter", fn.Func.Enter.Slice())
-		dumpslice("buildssa-body", fn.Nbody.Slice())
-		dumpslice("buildssa-exit", fn.Func.Exit.Slice())
+		dumplist("buildssa-enter", fn.Func.Enter)
+		dumplist("buildssa-body", fn.Nbody)
+		dumplist("buildssa-exit", fn.Func.Exit)
 	}
 
 	var s state