cmd/internal/obj: stop storing Text flags in From3

Prior to this CL, flags such as NOSPLIT
on ATEXT Progs were stored in From3.Offset.
Some but not all of those flags were also
duplicated into From.Sym.Attribute.

This CL migrates all of those flags into
From.Sym.Attribute and stops creating a From3.

A side-effect of this is that printing an
ATEXT Prog can no longer simply dump From3.Offset.
That's kind of good, since the raw flag value
wasn't very informative anyway, but it did
necessitate a bunch of updates to the cmd/asm tests.

The reason I'm doing this work now is that
avoiding storing flags in both From.Sym and From3.Offset
simplifies some other changes to fix the data
race first described in CL 40254.

This CL almost passes toolstash-check -all.
The only changes are in cases where the assembler
has decided that a function's flags may be altered,
e.g. to make a function with no calls in it NOSPLIT.
Prior to this CL, that information was not printed.

Sample before:

"".Ctz64 t=1 size=63 args=0x10 locals=0x0
	0x0000 00000 (/Users/josh/go/tip/src/runtime/internal/sys/intrinsics.go:35)	TEXT	"".Ctz64(SB), $0-16
	0x0000 00000 (/Users/josh/go/tip/src/runtime/internal/sys/intrinsics.go:35)	FUNCDATA	$0, gclocals·f207267fbf96a0178e8758c6e3e0ce28(SB)

Sample after:

"".Ctz64 t=1 nosplit size=63 args=0x10 locals=0x0
	0x0000 00000 (/Users/josh/go/tip/src/runtime/internal/sys/intrinsics.go:35)	TEXT	"".Ctz64(SB), NOSPLIT, $0-16
	0x0000 00000 (/Users/josh/go/tip/src/runtime/internal/sys/intrinsics.go:35)	FUNCDATA	$0, gclocals·f207267fbf96a0178e8758c6e3e0ce28(SB)

Observe the additional "nosplit" in the first line
and the additional "NOSPLIT" in the second line.

Updates #15756

Change-Id: I5c59bd8f3bdc7c780361f801d94a261f0aef3d13
Reviewed-on: https://go-review.googlesource.com/40495
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 45 insertions, 8 deletions

diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index d5d96f792e..fc0305344f 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -261,14 +261,6 @@ func (p *Prog) From3Type() AddrType {
 	return p.From3.Type
 }
 
-// From3Offset returns From3.Offset, or 0 when From3 is nil.
-func (p *Prog) From3Offset() int64 {
-	if p.From3 == nil {
-		return 0
-	}
-	return p.From3.Offset
-}
-
 // An As denotes an assembler opcode.
 // There are some portable opcodes, declared here in package obj,
 // that are common to all architectures.
@@ -347,6 +339,9 @@ const (
 	AttrCFunc
 	AttrNoSplit
 	AttrLeaf
+	AttrWrapper
+	AttrNeedCtxt
+	AttrNoFrame
 	AttrSeenGlobl
 	AttrOnList
 
@@ -379,6 +374,9 @@ func (a Attribute) SeenGlobl() bool     { return a&AttrSeenGlobl != 0 }
 func (a Attribute) OnList() bool        { return a&AttrOnList != 0 }
 func (a Attribute) ReflectMethod() bool { return a&AttrReflectMethod != 0 }
 func (a Attribute) Local() bool         { return a&AttrLocal != 0 }
+func (a Attribute) Wrapper() bool       { return a&AttrWrapper != 0 }
+func (a Attribute) NeedCtxt() bool      { return a&AttrNeedCtxt != 0 }
+func (a Attribute) NoFrame() bool       { return a&AttrNoFrame != 0 }
 
 func (a *Attribute) Set(flag Attribute, value bool) {
 	if value {
@@ -388,6 +386,45 @@ func (a *Attribute) Set(flag Attribute, value bool) {
 	}
 }
 
+var textAttrStrings = [...]struct {
+	bit Attribute
+	s   string
+}{
+	{bit: AttrDuplicateOK, s: "DUPOK"},
+	{bit: AttrMakeTypelink, s: ""},
+	{bit: AttrCFunc, s: "CFUNC"},
+	{bit: AttrNoSplit, s: "NOSPLIT"},
+	{bit: AttrLeaf, s: "LEAF"},
+	{bit: AttrSeenGlobl, s: ""},
+	{bit: AttrOnList, s: ""},
+	{bit: AttrReflectMethod, s: "REFLECTMETHOD"},
+	{bit: AttrLocal, s: "LOCAL"},
+	{bit: AttrWrapper, s: "WRAPPER"},
+	{bit: AttrNeedCtxt, s: "NEEDCTXT"},
+	{bit: AttrNoFrame, s: "NOFRAME"},
+}
+
+// TextAttrString formats a for printing in as part of a TEXT prog.
+func (a Attribute) TextAttrString() string {
+	var s string
+	for _, x := range textAttrStrings {
+		if a&x.bit != 0 {
+			if x.s != "" {
+				s += x.s + "|"
+			}
+			a &^= x.bit
+		}
+	}
+	if a != 0 {
+		s += fmt.Sprintf("UnknownAttribute(%d)|", a)
+	}
+	// Chop off trailing |, if present.
+	if len(s) > 0 {
+		s = s[:len(s)-1]
+	}
+	return s
+}
+
 // The compiler needs LSym to satisfy fmt.Stringer, because it stores
 // an LSym in ssa.ExternSymbol.
 func (s *LSym) String() string {