cmd/compile: simplify a few bits of the code

Remove an unused type, a few redundant returns and replace a few slice
append loops with a single append.

Change-Id: If07248180bae5631b5b152c6051d9635889997d5
Reviewed-on: https://go-review.googlesource.com/66851
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

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

@@ -663,9 +663,7 @@ func (p *exporter) typ(t *types.Type) {
 		// TODO(gri) Determine if they are already sorted
 		// in which case we can drop this step.
 		var methods []*types.Field
-		for _, m := range t.Methods().Slice() {
+		methods = append(methods, t.Methods().Slice()...)
-			methods = append(methods, m)
-		}
 		sort.Sort(methodbyname(methods))
 		p.int(len(methods))
 

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

@@ -157,7 +157,6 @@ func init1(n *Node, out *[]*Node) {
 	initlist = initlist[:last]
 
 	n.SetInitorder(InitDone)
-	return
 }
 
 // foundinitloop prints an init loop error and exits.

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

@@ -3789,7 +3789,6 @@ ret:
 
 	lineno = lno
 	n.SetWalkdef(1)
-	return
 }
 
 func checkmake(t *types.Type, arg string, n *Node) bool {

src/cmd/compile/internal/ssa/loopreschedchecks.go

@@ -267,8 +267,6 @@ func insertLoopReschedChecks(f *Func) {
 		sdom = newSparseTree(f, f.Idom())
 		fmt.Printf("after %s = %s\n", f.Name, sdom.treestructure(f.Entry))
 	}
-
-	return
 }
 
 // newPhiFor inserts a new Phi function into b,

src/cmd/compile/internal/ssa/regalloc.go

@@ -1715,14 +1715,10 @@ func (s *regAllocState) placeSpills() {
 		}
 		oldSched = append(oldSched[:0], b.Values[nphi:]...)
 		b.Values = b.Values[:nphi]
-		for _, v := range start[b.ID] {
+		b.Values = append(b.Values, start[b.ID]...)
-			b.Values = append(b.Values, v)
-		}
 		for _, v := range oldSched {
 			b.Values = append(b.Values, v)
-			for _, w := range after[v.ID] {
+			b.Values = append(b.Values, after[v.ID]...)
-				b.Values = append(b.Values, w)
-			}
 		}
 	}
 }
@@ -2211,12 +2207,6 @@ type liveInfo struct {
 	pos  src.XPos // source position of next use
 }
 
-// dblock contains information about desired & avoid registers at the end of a block.
-type dblock struct {
-	prefers []desiredStateEntry
-	avoid   regMask
-}
-
 // computeLive computes a map from block ID to a list of value IDs live at the end
 // of that block. Together with the value ID is a count of how many instructions
 // to the next use of that value. The resulting map is stored in s.live.