cmd/compile: cmd/internal/obj: cull dead code

This code is dead as a result of

* removing the Follow pass
* moving rotation detection from walk to ssa

Change-Id: I14599c85bedb4e3148347b547e724187920182c4
Reviewed-on: https://go-review.googlesource.com/36484
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -1411,15 +1411,6 @@ func (s *state) ssaShiftOp(op Op, t *Type, u *Type) ssa.Op {
 	return x
 }
 
-func (s *state) ssaRotateOp(op Op, t *Type) ssa.Op {
-	etype1 := s.concreteEtype(t)
-	x, ok := opToSSA[opAndType{op, etype1}]
-	if !ok {
-		s.Fatalf("unhandled rotate op %v etype=%s", op, etype1)
-	}
-	return x
-}
-
 // expr converts the expression n to ssa, adds it to s and returns the ssa result.
 func (s *state) expr(n *Node) *ssa.Value {
 	if !(n.Op == ONAME || n.Op == OLITERAL && n.Sym != nil) {

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

@@ -3234,37 +3234,6 @@ func finishcompare(n, r *Node, init *Nodes) *Node {
 	return nn
 }
 
-func samecheap(a *Node, b *Node) bool {
-	var ar *Node
-	var br *Node
-	for a != nil && b != nil && a.Op == b.Op {
-		switch a.Op {
-		default:
-			return false
-
-		case ONAME:
-			return a == b
-
-		case ODOT, ODOTPTR:
-			if a.Sym != b.Sym {
-				return false
-			}
-
-		case OINDEX:
-			ar = a.Right
-			br = b.Right
-			if !Isconst(ar, CTINT) || !Isconst(br, CTINT) || ar.Val().U.(*Mpint).Cmp(br.Val().U.(*Mpint)) != 0 {
-				return false
-			}
-		}
-
-		a = a.Left
-		b = b.Left
-	}
-
-	return false
-}
-
 // isIntOrdering reports whether n is a <, ≤, >, or ≥ ordering between integers.
 func (n *Node) isIntOrdering() bool {
 	switch n.Op {

src/cmd/internal/obj/pass.go

@@ -32,17 +32,6 @@ package obj
 
 // Code and data passes.
 
-func Brchain(ctxt *Link, p *Prog) *Prog {
-	for i := 0; i < 20; i++ {
-		if p == nil || p.As != AJMP || p.Pcond == nil {
-			return p
-		}
-		p = p.Pcond
-	}
-
-	return nil
-}
-
 func brloop(ctxt *Link, p *Prog) *Prog {
 	var q *Prog