cmd/internal/*: only call ctx.Bso.Flush when something has been written

In many places where ctx.Bso.Flush is used as the target for some debug
logging, ctx.Bso.Flush is called unconditionally. In the majority of
cases where debug logging is not enabled, this means Flush is called
many times when there is nothing to be flushed (it will be called anyway
when ctx.Bso is eventually closed), sometimes in a loop.

Avoid this by moving the ctx.Bso.Flush call into the same condition
block as the debug print. This pattern was previously applied
sporadically.

Change-Id: I0444cb235cc8b9bac51a59b2e44e59872db2be06
Reviewed-on: https://go-review.googlesource.com/27579
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/cmd/internal/obj/arm64/obj7.go

@@ -714,8 +714,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 			if ctxt.Autosize == 0 && !(cursym.Text.Mark&LEAF != 0) {
 				if ctxt.Debugvlog != 0 {
 					fmt.Fprintf(ctxt.Bso, "save suppressed in: %s\n", cursym.Text.From.Sym.Name)
+					ctxt.Bso.Flush()
 				}
-				ctxt.Bso.Flush()
 				cursym.Text.Mark |= LEAF
 			}
 

src/cmd/internal/obj/mips/obj0.go

@@ -145,8 +145,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	 */
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f noops\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	var q *obj.Prog
 	var q1 *obj.Prog

src/cmd/internal/obj/ppc64/obj9.go

@@ -276,8 +276,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	 */
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f noops\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	var q *obj.Prog
 	var q1 *obj.Prog

src/cmd/internal/obj/s390x/objz.go

@@ -243,8 +243,8 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 	 */
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f noops\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	var q *obj.Prog
 	var q1 *obj.Prog

src/cmd/link/internal/amd64/asm.go

@@ -601,13 +601,13 @@ func addgotsym(ctxt *ld.Link, s *ld.Symbol) {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f codeblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -625,8 +625,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -634,8 +634,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -679,8 +679,8 @@ func asmb(ctxt *ld.Link) {
 	if !*ld.FlagS {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 		case obj.Hplan9:
@@ -751,8 +751,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f headr\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

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

@@ -584,8 +584,8 @@ func addgotsym(ctxt *ld.Link, s *ld.Symbol) {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -602,8 +602,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -611,8 +611,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -634,8 +634,8 @@ func asmb(ctxt *ld.Link) {
 		// TODO: rationalize
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 			if ld.Iself {
@@ -690,8 +690,8 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Cursym = nil
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f header\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

src/cmd/link/internal/arm64/asm.go

@@ -393,8 +393,8 @@ func archrelocvariant(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, t int64) int64 {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -411,8 +411,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -420,8 +420,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -443,8 +443,8 @@ func asmb(ctxt *ld.Link) {
 		// TODO: rationalize
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 			if ld.Iself {
@@ -499,8 +499,8 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Cursym = nil
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f header\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

src/cmd/link/internal/ld/data.go

@@ -649,8 +649,8 @@ func relocsym(ctxt *Link, s *Symbol) {
 func (ctxt *Link) reloc() {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f reloc\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	for _, s := range ctxt.Textp {
 		relocsym(ctxt, s)
@@ -725,8 +725,8 @@ func dynreloc(ctxt *Link, data *[obj.SXREF][]*Symbol) {
 	}
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f reloc\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	for _, s := range ctxt.Textp {
 		dynrelocsym(ctxt, s)
@@ -805,9 +805,8 @@ func CodeblkPad(ctxt *Link, addr int64, size int64, pad []byte) {
 		for ; addr < eaddr; addr++ {
 			fmt.Fprintf(ctxt.Bso, " %.2x", 0)
 		}
+		ctxt.Bso.Flush()
 	}
-
-	ctxt.Bso.Flush()
 }
 
 func blk(ctxt *Link, syms []*Symbol, addr, size int64, pad []byte) {
@@ -1191,8 +1190,8 @@ var datap []*Symbol
 func (ctxt *Link) dodata() {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f dodata\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	// Collect data symbols by type into data.
 	var data [obj.SXREF][]*Symbol

src/cmd/link/internal/ld/lib.go

@@ -655,8 +655,8 @@ func objfile(ctxt *Link, lib *Library) {
 
 	if ctxt.Debugvlog > 1 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f ldobj: %s (%s)\n", obj.Cputime(), lib.File, pkg)
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	f, err := bio.Open(lib.File)
 	if err != nil {
 		Exitf("cannot open file %s: %v", lib.File, err)
@@ -1945,8 +1945,8 @@ func genasmsym(ctxt *Link, put func(*Link, *Symbol, string, int, int64, int64, i
 	// Something underhanded is going on. Say nothing.
 	if ctxt.Debugvlog != 0 || *flagN {
 		fmt.Fprintf(ctxt.Bso, "%5.2f symsize = %d\n", obj.Cputime(), uint32(Symsize))
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 }
 
 func Symaddr(ctxt *Link, s *Symbol) int64 {

src/cmd/link/internal/ld/main.go

@@ -176,8 +176,8 @@ func Main() {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "HEADER = -H%d -T0x%x -D0x%x -R0x%x\n", HEADTYPE, uint64(*FlagTextAddr), uint64(*FlagDataAddr), uint32(*FlagRound))
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if Buildmode == BuildmodeShared {
 		for i := 0; i < flag.NArg(); i++ {

src/cmd/link/internal/mips64/asm.go

@@ -185,8 +185,8 @@ func archrelocvariant(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, t int64) int64 {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -203,8 +203,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -212,8 +212,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -230,8 +230,8 @@ func asmb(ctxt *ld.Link) {
 		// TODO: rationalize
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 			if ld.Iself {
@@ -278,8 +278,8 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Cursym = nil
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f header\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

src/cmd/link/internal/ppc64/asm.go

@@ -806,8 +806,8 @@ func ensureglinkresolver(ctxt *ld.Link) *ld.Symbol {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -824,8 +824,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -833,8 +833,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -851,8 +851,8 @@ func asmb(ctxt *ld.Link) {
 		// TODO: rationalize
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 			if ld.Iself {
@@ -899,8 +899,8 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Cursym = nil
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f header\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

src/cmd/link/internal/s390x/asm.go

@@ -501,8 +501,8 @@ func addgotsym(ctxt *ld.Link, s *ld.Symbol) {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -519,8 +519,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -528,8 +528,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -548,8 +548,8 @@ func asmb(ctxt *ld.Link) {
 		}
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
 		symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
 
@@ -573,8 +573,8 @@ func asmb(ctxt *ld.Link) {
 	ctxt.Cursym = nil
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f header\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default:

src/cmd/link/internal/x86/asm.go

@@ -627,8 +627,8 @@ func addgotsym(ctxt *ld.Link, s *ld.Symbol) {
 func asmb(ctxt *ld.Link) {
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f asmb\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	if ld.Iself {
 		ld.Asmbelfsetup(ctxt)
@@ -646,8 +646,8 @@ func asmb(ctxt *ld.Link) {
 	if ld.Segrodata.Filelen > 0 {
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f rodatblk\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 
 		ld.Cseek(int64(ld.Segrodata.Fileoff))
 		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
@@ -655,8 +655,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f datblk\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 
 	ld.Cseek(int64(ld.Segdata.Fileoff))
 	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
@@ -677,8 +677,8 @@ func asmb(ctxt *ld.Link) {
 		// TODO: rationalize
 		if ctxt.Debugvlog != 0 {
 			fmt.Fprintf(ctxt.Bso, "%5.2f sym\n", obj.Cputime())
+			ctxt.Bso.Flush()
 		}
-		ctxt.Bso.Flush()
 		switch ld.HEADTYPE {
 		default:
 			if ld.Iself {
@@ -741,8 +741,8 @@ func asmb(ctxt *ld.Link) {
 
 	if ctxt.Debugvlog != 0 {
 		fmt.Fprintf(ctxt.Bso, "%5.2f headr\n", obj.Cputime())
+		ctxt.Bso.Flush()
 	}
-	ctxt.Bso.Flush()
 	ld.Cseek(0)
 	switch ld.HEADTYPE {
 	default: