cmd: some semi-automated cleanups

* Remove some redundant returns
* Replace HasPrefix with TrimPrefix
* Remove some obviously dead code

Passes toolstash -cmp on std cmd.

Change-Id: Ifb0d70a45cbb8a8553758a8c4878598b7fe932bc
Reviewed-on: https://go-review.googlesource.com/105017
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/asm/internal/arch/arm.go

@@ -223,9 +223,7 @@ func ParseARMCondition(cond string) (uint8, bool) {
 }
 
 func parseARMCondition(cond string, ls, scond map[string]uint8) (uint8, bool) {
-	if strings.HasPrefix(cond, ".") {
-		cond = cond[1:]
-	}
+	cond = strings.TrimPrefix(cond, ".")
 	if cond == "" {
 		return arm.C_SCOND_NONE, true
 	}

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

@@ -226,7 +226,6 @@ func (s *state) updateUnsetPredPos(b *ssa.Block) {
 		p.Pos = bestPos
 		s.updateUnsetPredPos(p) // We do not expect long chains of these, thus recursion is okay.
 	}
-	return
 }
 
 type state struct {

src/cmd/go/internal/test/test.go

@@ -722,9 +722,7 @@ func runTest(cmd *base.Command, args []string) {
 		buildTest, runTest, printTest, err := builderTest(&b, p)
 		if err != nil {
 			str := err.Error()
-			if strings.HasPrefix(str, "\n") {
-				str = str[1:]
-			}
+			str = strings.TrimPrefix(str, "\n")
 			failed := fmt.Sprintf("FAIL\t%s [setup failed]\n", p.ImportPath)
 
 			if p.ImportPath != "" {

src/cmd/internal/obj/arm/asm5.go

@@ -2844,7 +2844,6 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	out[3] = o4
 	out[4] = o5
 	out[5] = o6
-	return
 }
 
 func (c *ctxt5) movxt(p *obj.Prog) uint32 {
@@ -3315,8 +3314,7 @@ func (c *ctxt5) ofsr(a obj.As, r int, v int32, b int, sc int, p *obj.Prog) uint3
 
 // MOVW $"lower 16-bit", Reg
 func (c *ctxt5) omvs(p *obj.Prog, a *obj.Addr, dr int) uint32 {
-	var o1 uint32
-	o1 = ((uint32(p.Scond) & C_SCOND) ^ C_SCOND_XOR) << 28
+	o1 := ((uint32(p.Scond) & C_SCOND) ^ C_SCOND_XOR) << 28
 	o1 |= 0x30 << 20
 	o1 |= (uint32(dr) & 15) << 12
 	o1 |= uint32(a.Offset) & 0x0fff

src/cmd/internal/obj/arm64/asm7.go

@@ -1533,9 +1533,6 @@ func (c *ctxt7) oplook(p *obj.Prog) *Optab {
 	}
 
 	c.ctxt.Diag("illegal combination: %v %v %v %v, %d %d", p, DRconv(a1), DRconv(a2), DRconv(a3), p.From.Type, p.To.Type)
-	if ops == nil {
-		ops = optab
-	}
 	// Turn illegal instruction into an UNDEF, avoid crashing in asmout
 	return &Optab{obj.AUNDEF, C_NONE, C_NONE, C_NONE, 90, 4, 0, 0, 0}
 }
@@ -4264,7 +4261,6 @@ func (c *ctxt7) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	out[2] = o3
 	out[3] = o4
 	out[4] = o5
-	return
 }
 
 /*

src/cmd/internal/obj/mips/asm0.go

@@ -739,9 +739,6 @@ func (c *ctxt0) oplook(p *obj.Prog) *Optab {
 
 	c.ctxt.Diag("illegal combination %v %v %v %v", p.As, DRconv(a1), DRconv(a2), DRconv(a3))
 	prasm(p)
-	if ops == nil {
-		ops = optab
-	}
 	// Turn illegal instruction into an UNDEF, avoid crashing in asmout.
 	return &Optab{obj.AUNDEF, C_NONE, C_NONE, C_NONE, 49, 4, 0, 0}
 }
@@ -1602,7 +1599,6 @@ func (c *ctxt0) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	out[1] = o2
 	out[2] = o3
 	out[3] = o4
-	return
 }
 
 func (c *ctxt0) vregoff(a *obj.Addr) int64 {

src/cmd/internal/obj/ppc64/asm9.go

@@ -3560,7 +3560,6 @@ func (c *ctxt9) asmout(p *obj.Prog, o *Optab, out []uint32) {
 	out[2] = o3
 	out[3] = o4
 	out[4] = o5
-	return
 }
 
 func (c *ctxt9) vregoff(a *obj.Addr) int64 {

src/cmd/internal/obj/x86/a.out.go

@@ -32,11 +32,6 @@ package x86
 
 import "cmd/internal/obj"
 
-// mark flags
-const (
-	DONE = 1 << iota
-)
-
 const (
 	REG_NONE = 0
 )

src/cmd/internal/obj/x86/asm6.go

@@ -3168,7 +3168,6 @@ bas:
 bad:
 	ctxt.Diag("asmidx: bad address %d/%d/%d", scale, index, base)
 	ab.Put1(0)
-	return
 }
 
 func (ab *AsmBuf) relput4(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, a *obj.Addr) {
@@ -3436,7 +3435,6 @@ putrelv:
 
 bad:
 	ctxt.Diag("asmand: bad address %v", obj.Dconv(p, a))
-	return
 }
 
 func (ab *AsmBuf) asmand(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog, a *obj.Addr, ra *obj.Addr) {
@@ -4400,8 +4398,6 @@ func (ab *AsmBuf) doasm(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
 					ab.PutInt32(0)
 				}
 
-				break
-
 			case Zbyte:
 				v = vaddr(ctxt, p, &p.From, &rel)
 				if rel.Siz != 0 {
@@ -4776,7 +4772,6 @@ bad:
 
 	ctxt.Diag("invalid instruction: %v", p)
 	//	ctxt.Diag("doasm: notfound ft=%d tt=%d %v %d %d", p.Ft, p.Tt, p, oclass(ctxt, p, &p.From), oclass(ctxt, p, &p.To))
-	return
 }
 
 // byteswapreg returns a byte-addressable register (AX, BX, CX, DX)

src/cmd/internal/objabi/flag.go

@@ -106,21 +106,6 @@ func (c *count) IsCountFlag() bool {
 	return true
 }
 
-type fn0 func()
-
-func (f fn0) Set(s string) error {
-	f()
-	return nil
-}
-
-func (f fn0) Get() interface{} { return nil }
-
-func (f fn0) String() string { return "" }
-
-func (f fn0) IsBoolFlag() bool {
-	return true
-}
-
 type fn1 func(string)
 
 func (f fn1) Set(s string) error {

src/cmd/internal/objfile/disasm.go

@@ -141,9 +141,7 @@ func (fc *FileCache) Line(filename string, line int) ([]byte, error) {
 	// Clean filenames returned by src.Pos.SymFilename()
 	// or src.PosBase.SymFilename() removing
 	// the leading src.FileSymPrefix.
-	if strings.HasPrefix(filename, src.FileSymPrefix) {
-		filename = filename[len(src.FileSymPrefix):]
-	}
+	filename = strings.TrimPrefix(filename, src.FileSymPrefix)
 
 	// Expand literal "$GOROOT" rewrited by obj.AbsFile()
 	filename = filepath.Clean(os.ExpandEnv(filename))

src/cmd/link/internal/loadpe/ldpe.go

@@ -406,9 +406,7 @@ func readpesym(arch *sys.Arch, syms *sym.Symbols, f *pe.File, pesym *pe.COFFSymb
 		name = sectsyms[f.Sections[pesym.SectionNumber-1]].Name
 	} else {
 		name = symname
-		if strings.HasPrefix(name, "__imp_") {
-			name = name[6:] // __imp_Name => Name
-		}
+		name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
 		if arch.Family == sys.I386 && name[0] == '_' {
 			name = name[1:] // _Name => Name
 		}

src/cmd/vet/method.go

@@ -166,9 +166,7 @@ func (f *File) matchParams(expect []string, actual []ast.Expr, prefix string) bo
 
 // Does this one type match?
 func (f *File) matchParamType(expect string, actual ast.Expr) bool {
-	if strings.HasPrefix(expect, "=") {
-		expect = expect[1:]
-	}
+	expect = strings.TrimPrefix(expect, "=")
 	// Strip package name if we're in that package.
 	if n := len(f.file.Name.Name); len(expect) > n && expect[:n] == f.file.Name.Name && expect[n] == '.' {
 		expect = expect[n+1:]