cmd: remove Go115AMD64

Always do aligned jumps now.

Change-Id: If68a16fe93c9173c83323a9063465c9bd166eeb8
Reviewed-on: https://go-review.googlesource.com/c/go/+/266857
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/asm/internal/asm/endtoend_test.go

@@ -390,12 +390,7 @@ func TestARM64Errors(t *testing.T) {
 }
 
 func TestAMD64EndToEnd(t *testing.T) {
-	defer func(old string) { objabi.GOAMD64 = old }(objabi.GOAMD64)
-	for _, goamd64 := range []string{"normaljumps", "alignedjumps"} {
-		t.Logf("GOAMD64=%s", goamd64)
-		objabi.GOAMD64 = goamd64
 	testEndToEnd(t, "amd64", "amd64")
-	}
 }
 
 func Test386Encoder(t *testing.T) {

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

@@ -1851,9 +1851,9 @@ func spadjop(ctxt *obj.Link, l, q obj.As) obj.As {
 	return q
 }
 
-// If the environment variable GOAMD64=alignedjumps the assembler will ensure that
-// no standalone or macro-fused jump will straddle or end on a 32 byte boundary
-// by inserting NOPs before the jumps
+// isJump returns whether p is a jump instruction.
+// It is used to ensure that no standalone or macro-fused jump will straddle
+// or end on a 32 byte boundary by inserting NOPs before the jumps.
 func isJump(p *obj.Prog) bool {
 	return p.To.Target() != nil || p.As == obj.AJMP || p.As == obj.ACALL ||
 		p.As == obj.ARET || p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO
@@ -1987,11 +1987,6 @@ func makePjcCtx(ctxt *obj.Link) padJumpsCtx {
 		return padJumpsCtx(0)
 	}
 
-	if objabi.GOAMD64 != "alignedjumps" {
-		return padJumpsCtx(0)
-
-	}
-
 	return padJumpsCtx(32)
 }
 

src/cmd/internal/objabi/util.go

@@ -25,7 +25,6 @@ var (
 	GOARCH   = envOr("GOARCH", defaultGOARCH)
 	GOOS     = envOr("GOOS", defaultGOOS)
 	GO386    = envOr("GO386", defaultGO386)
-	GOAMD64  = goamd64()
 	GOARM    = goarm()
 	GOMIPS   = gomips()
 	GOMIPS64 = gomips64()
@@ -38,14 +37,8 @@ var (
 const (
 	ElfRelocOffset   = 256
 	MachoRelocOffset = 2048 // reserve enough space for ELF relocations
-	Go115AMD64       = "alignedjumps" // Should be "alignedjumps" or "normaljumps"; this replaces environment variable introduced in CL 219357.
 )
 
-// TODO(1.16): assuming no issues in 1.15 release, remove this and related constant.
-func goamd64() string {
-	return Go115AMD64
-}
-
 func goarm() int {
 	switch v := envOr("GOARM", defaultGOARM); v {
 	case "5":

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

@@ -33,7 +33,7 @@ package amd64
 const (
 	maxAlign  = 32 // max data alignment
 	minAlign  = 1  // min data alignment
-	funcAlign = 16
+	funcAlign = 32
 )
 
 /* Used by ../internal/ld/dwarf.go */

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

@@ -39,13 +39,8 @@ import (
 func Init() (*sys.Arch, ld.Arch) {
 	arch := sys.ArchAMD64
 
-	fa := funcAlign
-	if objabi.GOAMD64 == "alignedjumps" {
-		fa = 32
-	}
-
 	theArch := ld.Arch{
-		Funcalign:  fa,
+		Funcalign:  funcAlign,
 		Maxalign:   maxAlign,
 		Minalign:   minAlign,
 		Dwarfregsp: dwarfRegSP,