cmd/internal/objabi: extract shared functionality from obj

Now only cmd/asm and cmd/compile depend on cmd/internal/obj. Changing
the assembler backends no longer requires reinstalling cmd/link or
cmd/addr2line.

There's also now one canonical definition of the object file format in
cmd/internal/objabi/doc.go, with a warning to update all three
implementations.

objabi is still something of a grab bag of unrelated code (e.g., flag
and environment variable handling probably belong in a separate "tool"
package), but this is still progress.

Fixes #15165.
Fixes #20026.

Change-Id: Ic4b92fac7d0d35438e0d20c9579aad4085c5534c
Reviewed-on: https://go-review.googlesource.com/40972
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

2 files changed, 27 insertions, 25 deletions

diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go
index 4725737b2b..4476439350 100644
--- a/src/cmd/internal/obj/arm/asm5.go
+++ b/src/cmd/internal/obj/arm/asm5.go
@@ -32,6 +32,7 @@ package arm
 
 import (
 	"cmd/internal/obj"
+	"cmd/internal/objabi"
 	"fmt"
 	"log"
 	"math"
@@ -602,7 +603,7 @@ func span5(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 
 		p.Pc = int64(pc)
 		o = c.oplook(p)
-		if ctxt.Headtype != obj.Hnacl {
+		if ctxt.Headtype != objabi.Hnacl {
 			m = int(o.size)
 		} else {
 			m = c.asmoutnacl(pc, p, o, nil)
@@ -696,7 +697,7 @@ func span5(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 			*/
 			opc = int32(p.Pc)
 
-			if ctxt.Headtype != obj.Hnacl {
+			if ctxt.Headtype != objabi.Hnacl {
 				m = int(o.size)
 			} else {
 				m = c.asmoutnacl(pc, p, o, nil)
@@ -756,7 +757,7 @@ func span5(ctxt *obj.Link, cursym *obj.LSym, newprog obj.ProgAlloc) {
 		c.pc = p.Pc
 		o = c.oplook(p)
 		opc = int32(p.Pc)
-		if ctxt.Headtype != obj.Hnacl {
+		if ctxt.Headtype != objabi.Hnacl {
 			c.asmout(p, o, out[:])
 			m = int(o.size)
 		} else {
@@ -834,7 +835,7 @@ func (c *ctxt5) flushpool(p *obj.Prog, skip int, force int) bool {
 		} else if force == 0 && (p.Pc+int64(12+c.pool.size)-int64(c.pool.start) < 2048) { // 12 take into account the maximum nacl literal pool alignment padding size
 			return false
 		}
-		if c.ctxt.Headtype == obj.Hnacl && c.pool.size%16 != 0 {
+		if c.ctxt.Headtype == objabi.Hnacl && c.pool.size%16 != 0 {
 			// if pool is not multiple of 16 bytes, add an alignment marker
 			q := c.newprog()
 
@@ -902,7 +903,7 @@ func (c *ctxt5) addpool(p *obj.Prog, a *obj.Addr) {
 		}
 	}
 
-	if c.ctxt.Headtype == obj.Hnacl && c.pool.size%16 == 0 {
+	if c.ctxt.Headtype == objabi.Hnacl && c.pool.size%16 == 0 {
 		// start a new data bundle
 		q := c.newprog()
 		q.As = ADATABUNDLE
@@ -1019,7 +1020,7 @@ func (c *ctxt5) aclass(a *obj.Addr) int {
 			}
 
 			c.instoffset = 0 // s.b. unused but just in case
-			if a.Sym.Type == obj.STLSBSS {
+			if a.Sym.Type == objabi.STLSBSS {
 				if c.ctxt.Flag_shared {
 					return C_TLS_IE
 				} else {
@@ -1584,7 +1585,7 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 			rel.Sym = p.To.Sym
 			v += int32(p.To.Offset)
 			rel.Add = int64(o1) | (int64(v)>>2)&0xffffff
-			rel.Type = obj.R_CALLARM
+			rel.Type = objabi.R_CALLARM
 			break
 		}
 
@@ -1612,7 +1613,7 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		rel := obj.Addrel(c.cursym)
 		rel.Off = int32(c.pc)
 		rel.Siz = 0
-		rel.Type = obj.R_CALLIND
+		rel.Type = objabi.R_CALLIND
 
 	case 8: /* sll $c,[R],R -> mov (R<<$c),R */
 		c.aclass(&p.From)
@@ -1661,13 +1662,13 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 
 			if c.ctxt.Flag_shared {
 				if p.To.Name == obj.NAME_GOTREF {
-					rel.Type = obj.R_GOTPCREL
+					rel.Type = objabi.R_GOTPCREL
 				} else {
-					rel.Type = obj.R_PCREL
+					rel.Type = objabi.R_PCREL
 				}
 				rel.Add += c.pc - p.Rel.Pc - 8
 			} else {
-				rel.Type = obj.R_ADDR
+				rel.Type = objabi.R_ADDR
 			}
 			o1 = 0
 		}
@@ -2080,7 +2081,7 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		rel.Off = int32(c.pc)
 		rel.Siz = 4
 		rel.Sym = p.To.Sym
-		rel.Type = obj.R_TLS_LE
+		rel.Type = objabi.R_TLS_LE
 		o1 = 0
 
 	case 104: /* word tlsvar, initial exec */
@@ -2094,7 +2095,7 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		rel.Off = int32(c.pc)
 		rel.Siz = 4
 		rel.Sym = p.To.Sym
-		rel.Type = obj.R_TLS_IE
+		rel.Type = objabi.R_TLS_IE
 		rel.Add = c.pc - p.Rel.Pc - 8 - int64(rel.Siz)
 
 	case 68: /* floating point store -> ADDR */
@@ -2849,7 +2850,7 @@ func (c *ctxt5) omvl(p *obj.Prog, a *obj.Addr, dr int) uint32 {
 
 func (c *ctxt5) chipzero5(e float64) int {
 	// We use GOARM=7 to gate the use of VFPv3 vmov (imm) instructions.
-	if obj.GOARM < 7 || e != 0 {
+	if objabi.GOARM < 7 || e != 0 {
 		return -1
 	}
 	return 0
@@ -2857,7 +2858,7 @@ func (c *ctxt5) chipzero5(e float64) int {
 
 func (c *ctxt5) chipfloat5(e float64) int {
 	// We use GOARM=7 to gate the use of VFPv3 vmov (imm) instructions.
-	if obj.GOARM < 7 {
+	if objabi.GOARM < 7 {
 		return -1
 	}
 
diff --git a/src/cmd/internal/obj/arm/obj5.go b/src/cmd/internal/obj/arm/obj5.go
index cb34d16705..49a24c9b5f 100644
--- a/src/cmd/internal/obj/arm/obj5.go
+++ b/src/cmd/internal/obj/arm/obj5.go
@@ -32,6 +32,7 @@ package arm
 
 import (
 	"cmd/internal/obj"
+	"cmd/internal/objabi"
 	"cmd/internal/sys"
 )
 
@@ -62,7 +63,7 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 				ctxt.Diag("%v: TLS MRC instruction must write to R0 as it might get translated into a BL instruction", p.Line())
 			}
 
-			if obj.GOARM < 7 {
+			if objabi.GOARM < 7 {
 				// Replace it with BL runtime.read_tls_fallback(SB) for ARM CPUs that lack the tls extension.
 				if progedit_tlsfallback == nil {
 					progedit_tlsfallback = ctxt.Lookup("runtime.read_tls_fallback", 0)
@@ -205,7 +206,7 @@ func (c *ctxt5) rewriteToUseGot(p *obj.Prog) {
 	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
 		return
 	}
-	if source.Sym.Type == obj.STLSBSS {
+	if source.Sym.Type == objabi.STLSBSS {
 		return
 	}
 	if source.Type != obj.TYPE_MEM {
@@ -632,7 +633,7 @@ func isfloatreg(a *obj.Addr) bool {
 }
 
 func (c *ctxt5) softfloat() {
-	if obj.GOARM > 5 {
+	if objabi.GOARM > 5 {
 		return
 	}
 
@@ -722,7 +723,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	p.To.Type = obj.TYPE_REG
 	p.To.Reg = REG_R1
 
-	if framesize <= obj.StackSmall {
+	if framesize <= objabi.StackSmall {
 		// small stack: SP < stackguard
 		//	CMP	stackguard, SP
 		p = obj.Appendp(p, c.newprog)
@@ -731,7 +732,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = REG_R1
 		p.Reg = REGSP
-	} else if framesize <= obj.StackBig {
+	} else if framesize <= objabi.StackBig {
 		// large stack: SP-framesize < stackguard-StackSmall
 		//	MOVW $-(framesize-StackSmall)(SP), R2
 		//	CMP stackguard, R2
@@ -740,7 +741,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p.As = AMOVW
 		p.From.Type = obj.TYPE_ADDR
 		p.From.Reg = REGSP
-		p.From.Offset = -(int64(framesize) - obj.StackSmall)
+		p.From.Offset = -(int64(framesize) - objabi.StackSmall)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2
 
@@ -764,14 +765,14 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 
 		p.As = ACMP
 		p.From.Type = obj.TYPE_CONST
-		p.From.Offset = int64(uint32(obj.StackPreempt & (1<<32 - 1)))
+		p.From.Offset = int64(uint32(objabi.StackPreempt & (1<<32 - 1)))
 		p.Reg = REG_R1
 
 		p = obj.Appendp(p, c.newprog)
 		p.As = AMOVW
 		p.From.Type = obj.TYPE_ADDR
 		p.From.Reg = REGSP
-		p.From.Offset = obj.StackGuard
+		p.From.Offset = objabi.StackGuard
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R2
 		p.Scond = C_SCOND_NE
@@ -787,7 +788,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 		p = obj.Appendp(p, c.newprog)
 		p.As = AMOVW
 		p.From.Type = obj.TYPE_ADDR
-		p.From.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
+		p.From.Offset = int64(framesize) + (objabi.StackGuard - objabi.StackSmall)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = REG_R3
 		p.Scond = C_SCOND_NE
@@ -820,7 +821,7 @@ func (c *ctxt5) stacksplit(p *obj.Prog, framesize int32) *obj.Prog {
 	pcdata.Pos = c.cursym.Func.Text.Pos
 	pcdata.As = obj.APCDATA
 	pcdata.From.Type = obj.TYPE_CONST
-	pcdata.From.Offset = obj.PCDATA_StackMapIndex
+	pcdata.From.Offset = objabi.PCDATA_StackMapIndex
 	pcdata.To.Type = obj.TYPE_CONST
 	pcdata.To.Offset = -1 // pcdata starts at -1 at function entry