Revert "cmd/asm: align an instruction or a function's address"

This reverts CL 212767.

Reason for revert: new test is persistently failing on freebsd-arm64-dmgk builder.

Change-Id: Ifd1227628e0e747688ddb4dc580170b2a103a89e
Reviewed-on: https://go-review.googlesource.com/c/go/+/226597
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/goobj/read.go

@@ -95,7 +95,6 @@ type Var struct {
 type Func struct {
 	Args     int64      // size in bytes of argument frame: inputs and outputs
 	Frame    int64      // size in bytes of local variable frame
-	Align    uint32     // alignment requirement in bytes for the address of the function
 	Leaf     bool       // function omits save of link register (ARM)
 	NoSplit  bool       // function omits stack split prologue
 	TopFrame bool       // function is the top of the call stack
@@ -591,7 +590,6 @@ func (r *objReader) parseObject(prefix []byte) error {
 			s.Func = f
 			f.Args = r.readInt()
 			f.Frame = r.readInt()
-			f.Align = uint32(r.readInt())
 			flags := r.readInt()
 			f.Leaf = flags&(1<<0) != 0
 			f.TopFrame = flags&(1<<4) != 0

src/cmd/internal/goobj/readnew.go

@@ -149,7 +149,6 @@ func (r *objReader) readNew() {
 		f := &Func{
 			Args:     int64(info.Args),
 			Frame:    int64(info.Locals),
-			Align:    info.Align,
 			NoSplit:  info.NoSplit != 0,
 			Leaf:     osym.Leaf(),
 			TopFrame: osym.TopFrame(),

src/cmd/internal/goobj2/funcinfo.go

@@ -18,7 +18,6 @@ type FuncInfo struct {
 
 	Args   uint32
 	Locals uint32
-	Align  uint32
 
 	Pcsp        uint32
 	Pcfile      uint32
@@ -43,7 +42,6 @@ func (a *FuncInfo) Write(w *bytes.Buffer) {
 
 	writeUint32(a.Args)
 	writeUint32(a.Locals)
-	writeUint32(a.Align)
 
 	writeUint32(a.Pcsp)
 	writeUint32(a.Pcfile)
@@ -81,7 +79,6 @@ func (a *FuncInfo) Read(b []byte) {
 
 	a.Args = readUint32()
 	a.Locals = readUint32()
-	a.Align = readUint32()
 
 	a.Pcsp = readUint32()
 	a.Pcfile = readUint32()

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

@@ -886,10 +886,25 @@ const OP_NOOP = 0xd503201f
 
 // align code to a certain length by padding bytes.
 func pcAlignPadLength(pc int64, alignedValue int64, ctxt *obj.Link) int {
-	if !((alignedValue&(alignedValue-1) == 0) && 8 <= alignedValue && alignedValue <= 2048) {
+	switch alignedValue {
-		ctxt.Diag("alignment value of an instruction must be a power of two and in the range [8, 2048], got %d\n", alignedValue)
+	case 8:
+		if pc%8 == 4 {
+			return 4
+		}
+	case 16:
+		switch pc % 16 {
+		case 4:
+			return 12
+		case 8:
+			return 8
+		case 12:
+			return 4
+		}
+	default:
+		ctxt.Diag("Unexpected alignment: %d for PCALIGN directive\n", alignedValue)
 	}
-	return int(-pc & (alignedValue - 1))
+
+	return 0
 }
 
 func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
@@ -925,12 +940,8 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 		if m == 0 {
 			switch p.As {
 			case obj.APCALIGN:
-				alignedValue := p.From.Offset
+				a := p.From.Offset
-				m = pcAlignPadLength(pc, alignedValue, ctxt)
+				m = pcAlignPadLength(pc, a, ctxt)
-				// Update the current text symbol ailgnment value.
-				if int32(alignedValue) > cursym.Func.Align {
-					cursym.Func.Align = int32(alignedValue)
-				}
 				break
 			case obj.ANOP, obj.AFUNCDATA, obj.APCDATA:
 				continue
@@ -1006,8 +1017,8 @@ func span7(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 			if m == 0 {
 				switch p.As {
 				case obj.APCALIGN:
-					alignedValue := p.From.Offset
+					a := p.From.Offset
-					m = pcAlignPadLength(pc, alignedValue, ctxt)
+					m = pcAlignPadLength(pc, a, ctxt)
 					break
 				case obj.ANOP, obj.AFUNCDATA, obj.APCDATA:
 					continue

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

@@ -18,9 +18,7 @@ import (
 
 // TestLarge generates a very large file to verify that large
 // program builds successfully, in particular, too-far
-// conditional branches are fixed, and also verify that the
+// conditional branches are fixed.
-// instruction's pc can be correctly aligned even when branches
-// need to be fixed.
 func TestLarge(t *testing.T) {
 	if testing.Short() {
 		t.Skip("Skip in short mode")
@@ -43,27 +41,10 @@ func TestLarge(t *testing.T) {
 		t.Fatalf("can't write output: %v\n", err)
 	}
 
-	pattern := `0x0080\s00128\s\(.*\)\tMOVD\t\$3,\sR3`
+	// build generated file
-
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
-	// assemble generated file
-	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-S", "-o", filepath.Join(dir, "test.o"), tmpfile)
 	cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
 	out, err := cmd.CombinedOutput()
-	if err != nil {
-		t.Errorf("Assemble failed: %v, output: %s", err, out)
-	}
-	matched, err := regexp.MatchString(pattern, string(out))
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !matched {
-		t.Errorf("The alignment is not correct: %t, output:%s\n", matched, out)
-	}
-
-	// build generated file
-	cmd = exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
-	cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
-	out, err = cmd.CombinedOutput()
 	if err != nil {
 		t.Errorf("Build failed: %v, output: %s", err, out)
 	}
@@ -75,8 +56,6 @@ func gen(buf *bytes.Buffer) {
 	fmt.Fprintln(buf, "TBZ $5, R0, label")
 	fmt.Fprintln(buf, "CBZ R0, label")
 	fmt.Fprintln(buf, "BEQ label")
-	fmt.Fprintln(buf, "PCALIGN $128")
-	fmt.Fprintln(buf, "MOVD $3, R3")
 	for i := 0; i < 1<<19; i++ {
 		fmt.Fprintln(buf, "MOVD R0, R1")
 	}

src/cmd/internal/obj/link.go

@@ -398,7 +398,6 @@ type LSym struct {
 type FuncInfo struct {
 	Args     int32
 	Locals   int32
-	Align    int32
 	Text     *Prog
 	Autot    map[*LSym]struct{}
 	Pcln     Pcln

src/cmd/internal/obj/objfile.go

@@ -346,7 +346,6 @@ func (w *objWriter) writeSym(s *LSym) {
 
 	w.writeInt(int64(s.Func.Args))
 	w.writeInt(int64(s.Func.Locals))
-	w.writeInt(int64(s.Func.Align))
 	w.writeBool(s.NoSplit())
 	flags = int64(0)
 	if s.Leaf() {

src/cmd/internal/obj/objfile2.go

@@ -374,7 +374,6 @@ func genFuncInfoSyms(ctxt *Link) {
 			NoSplit: nosplit,
 			Args:    uint32(s.Func.Args),
 			Locals:  uint32(s.Func.Locals),
-			Align:   uint32(s.Func.Align),
 		}
 		pc := &s.Func.Pcln
 		o.Pcsp = pcdataoff

src/cmd/internal/obj/plist.go

@@ -133,13 +133,6 @@ func (ctxt *Link) InitTextSym(s *LSym, flag int) {
 	s.Set(AttrNeedCtxt, flag&NEEDCTXT != 0)
 	s.Set(AttrNoFrame, flag&NOFRAME != 0)
 	s.Set(AttrTopFrame, flag&TOPFRAME != 0)
-	if flag&ALIGN2048 != 0 {
-		if objabi.GOARCH != "arm64" {
-			ctxt.Diag("ALIGN2048 flag only works on ARM64 at present.")
-		}
-		s.Func.Align = 2048
-	}
-
 	s.Type = objabi.STEXT
 	ctxt.Text = append(ctxt.Text, s)
 

src/cmd/internal/obj/textflag.go

@@ -51,9 +51,4 @@ const (
 	// Function is the top of the call stack. Call stack unwinders should stop
 	// at this function.
 	TOPFRAME = 2048
-
-	// ALIGN2048 means that the address of the function must be aligned to a
-	// 2048 bytes boundary.
-	// Only works on arm64 at present.
-	ALIGN2048 = 4096
 )

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

@@ -2119,10 +2119,6 @@ func assignAddress(ctxt *Link, sect *sym.Section, n int, s *sym.Symbol, va uint6
 		funcsize = uint64(s.Size)
 	}
 
-	if sect.Align < s.Align {
-		sect.Align = s.Align
-	}
-
 	// On ppc64x a text section should not be larger than 2^26 bytes due to the size of
 	// call target offset field in the bl instruction.  Splitting into smaller text
 	// sections smaller than this limit allows the GNU linker to modify the long calls

src/cmd/link/internal/loader/loader.go

@@ -1227,7 +1227,6 @@ func loadObjFull(l *Loader, r *oReader) {
 		info.Pcdata = append(info.Pcdata, info.PcdataEnd) // for the ease of knowing where it ends
 		pc.Args = int32(info.Args)
 		pc.Locals = int32(info.Locals)
-		s.Align = int32(info.Align)
 
 		npc := len(info.Pcdata) - 1 // -1 as we appended one above
 		pc.Pcdata = pcDataBatch[:npc:npc]

src/cmd/link/internal/objfile/objfile.go

@@ -312,7 +312,6 @@ overwrite:
 
 		pc.Args = r.readInt32()
 		pc.Locals = r.readInt32()
-		s.Align = r.readInt32()
 		if r.readUint8() != 0 {
 			s.Attr |= sym.AttrNoSplit
 		}

src/cmd/link/link_test.go

@@ -3,7 +3,6 @@ package main
 import (
 	"bufio"
 	"bytes"
-	"cmd/internal/objabi"
 	"debug/macho"
 	"internal/testenv"
 	"io/ioutil"
@@ -448,103 +447,3 @@ func TestStrictDup(t *testing.T) {
 		t.Errorf("unexpected output:\n%s", out)
 	}
 }
-
-const testFuncAlignSrc = `
-package main
-import (
-	"fmt"
-	"reflect"
-)
-func alignFunc()
-func alignPc()
-
-func main() {
-	addr1 := reflect.ValueOf(alignFunc).Pointer()
-	addr2 := reflect.ValueOf(alignPc).Pointer()
-	switch {
-	case (addr1 % 2048) != 0 && (addr2 % 512) != 0:
-		fmt.Printf("expected 2048 bytes alignment, got %v; expected 512 bytes alignment, got %v\n", addr1, addr2)
-	case (addr2 % 512) != 0:
-		fmt.Printf("expected 512 bytes alignment, got %v\n", addr2)
-	case (addr1 % 2048) != 0:
-		fmt.Printf("expected 2048 bytes alignment, got %v\n", addr1)
-	default:
-		fmt.Printf("PASS")
-	}
-}
-`
-
-const testFuncAlignAsmSrc = `
-#include "textflag.h"
-TEXT	·alignFunc(SB),NOSPLIT|ALIGN2048, $0-0
-	MOVD	$1, R0
-	MOVD	$2, R1
-	RET
-
-TEXT	·alignPc(SB),NOSPLIT, $0-0
-	MOVD	$2, R0
-	PCALIGN	$512
-	MOVD	$3, R1
-	RET
-`
-
-// TestFuncAlign verifies that the address of a function can be aligned
-// with a specfic value on arm64.
-func TestFuncAlign(t *testing.T) {
-	if objabi.GOARCH != "arm64" {
-		t.Skipf("Skipping FuncAlign test on %s", objabi.GOARCH)
-	}
-	testenv.MustHaveGoBuild(t)
-
-	tmpdir, err := ioutil.TempDir("", "TestFuncAlign")
-	if err != nil {
-		t.Fatal(err)
-	}
-	defer os.RemoveAll(tmpdir)
-
-	src := filepath.Join(tmpdir, "falign.go")
-	err = ioutil.WriteFile(src, []byte(testFuncAlignSrc), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-	src = filepath.Join(tmpdir, "falign.s")
-	err = ioutil.WriteFile(src, []byte(testFuncAlignAsmSrc), 0666)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// Build and run with old object file format.
-	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", "falign")
-	cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
-	cmd.Dir = tmpdir
-	out, err := cmd.CombinedOutput()
-	if err != nil {
-		t.Errorf("build failed: %v", err)
-	}
-	cmd = exec.Command(tmpdir + "/falign")
-	out, err = cmd.CombinedOutput()
-	if err != nil {
-		t.Errorf("failed to run with err %v, output: %s", err, out)
-	}
-	if string(out) != "PASS" {
-		t.Errorf("unexpected output: %s\n", out)
-	}
-
-	// Build and run with new object file format.
-	cmd = exec.Command(testenv.GoToolPath(t), "build", "-o", "falign", "-gcflags=all=-newobj", "-asmflags=all=-newobj", "-ldflags=-newobj")
-	cmd.Env = append(os.Environ(), "GOARCH=arm64", "GOOS=linux")
-	cmd.Dir = tmpdir
-	out, err = cmd.CombinedOutput()
-	if err != nil {
-		t.Errorf("build with newobj failed: %v", err)
-	}
-	cmd = exec.Command(tmpdir + "/falign")
-	out, err = cmd.CombinedOutput()
-	if err != nil {
-		t.Errorf("failed to run with -newobj, err: %v, output: %s", err, out)
-	}
-	if string(out) != "PASS" {
-		t.Errorf("unexpected output with -newobj: %s\n", out)
-	}
-
-}

src/runtime/textflag.h

@@ -35,8 +35,3 @@
 // Function is the top of the call stack. Call stack unwinders should stop
 // at this function.
 #define TOPFRAME 2048
-// ALIGN2048 means that the address of the function must be aligned to a
-// 2048 bytes boundary.
-// Only works on arm64 at present.
-#define ALIGN2048 4096
-