cmd/compile, cmd/internal/obj: centralize knowledge of size of fixed part of stack

Shared libraries on ppc64le will require a larger minimum stack frame (because
the ABI mandates that the TOC pointer is available at 24(R1)). Part 2a of
preparing for that is to have all bits of arch-independent and ppc64-specific
codegen that need to know call a function to find out.

Change-Id: I55899f73037e92227813c491049a3bd6f30bd41f
Reviewed-on: https://go-review.googlesource.com/15524Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/gc/cgen.go

@@ -810,10 +810,7 @@ func cgen_wbptr(n, res *Node) {
 	a := &p.To
 	a.Type = obj.TYPE_MEM
 	a.Reg = int16(Thearch.REGSP)
-	a.Offset = 0
-	if HasLinkRegister() {
-		a.Offset += int64(Widthptr)
-	}
+	a.Offset = Ctxt.FixedFrameSize()
 	p2 := Thearch.Gins(Thearch.Optoas(OAS, Types[Tptr]), &src, nil)
 	p2.To = p.To
 	p2.To.Offset += int64(Widthptr)
@@ -849,10 +846,7 @@ func cgen_wbfat(n, res *Node) {
 	a := &p.To
 	a.Type = obj.TYPE_MEM
 	a.Reg = int16(Thearch.REGSP)
-	a.Offset = 0
-	if HasLinkRegister() {
-		a.Offset += int64(Widthptr)
-	}
+	a.Offset = Ctxt.FixedFrameSize()
 	if needType {
 		a.Offset += int64(Widthptr)
 	}
@@ -1686,10 +1680,7 @@ func Igen(n *Node, a *Node, res *Node) {
 		a.Op = OINDREG
 		a.Reg = int16(Thearch.REGSP)
 		a.Addable = true
-		a.Xoffset = fp.Width
-		if HasLinkRegister() {
-			a.Xoffset += int64(Ctxt.Arch.Ptrsize)
-		}
+		a.Xoffset = fp.Width + Ctxt.FixedFrameSize()
 		a.Type = n.Type
 		return
 
@@ -2219,11 +2210,7 @@ func stkof(n *Node) int64 {
 		var flist Iter
 		t = Structfirst(&flist, Getoutarg(t))
 		if t != nil {
-			w := t.Width
-			if HasLinkRegister() {
-				w += int64(Ctxt.Arch.Ptrsize)
-			}
-			return w
+			return t.Width + Ctxt.FixedFrameSize()
 		}
 	}
 
@@ -2379,17 +2366,11 @@ func Ginscall(f *Node, proc int) {
 		// size of arguments at 0(SP)
 		stk.Op = OINDREG
 		stk.Reg = int16(Thearch.REGSP)
-		stk.Xoffset = 0
-		if HasLinkRegister() {
-			stk.Xoffset += int64(Ctxt.Arch.Ptrsize)
-		}
+		stk.Xoffset = Ctxt.FixedFrameSize()
 		Thearch.Ginscon(Thearch.Optoas(OAS, Types[TINT32]), int64(Argsize(f.Type)), &stk)
 
 		// FuncVal* at 8(SP)
-		stk.Xoffset = int64(Widthptr)
-		if HasLinkRegister() {
-			stk.Xoffset += int64(Ctxt.Arch.Ptrsize)
-		}
+		stk.Xoffset = int64(Widthptr) + Ctxt.FixedFrameSize()
 
 		var reg Node
 		Nodreg(&reg, Types[Tptr], Thearch.REGCALLX2)
@@ -2447,10 +2428,7 @@ func cgen_callinter(n *Node, res *Node, proc int) {
 
 	var nodsp Node
 	Nodindreg(&nodsp, Types[Tptr], Thearch.REGSP)
-	nodsp.Xoffset = 0
-	if HasLinkRegister() {
-		nodsp.Xoffset += int64(Ctxt.Arch.Ptrsize)
-	}
+	nodsp.Xoffset = Ctxt.FixedFrameSize()
 	if proc != 0 {
 		nodsp.Xoffset += 2 * int64(Widthptr) // leave room for size & fn
 	}
@@ -2541,11 +2519,6 @@ func cgen_call(n *Node, proc int) {
 	Ginscall(n.Left, proc)
 }
 
-func HasLinkRegister() bool {
-	c := Ctxt.Arch.Thechar
-	return c != '6' && c != '8'
-}
-
 /*
  * call to n has already been generated.
  * generate:
@@ -2568,10 +2541,7 @@ func cgen_callret(n *Node, res *Node) {
 	nod.Reg = int16(Thearch.REGSP)
 	nod.Addable = true
 
-	nod.Xoffset = fp.Width
-	if HasLinkRegister() {
-		nod.Xoffset += int64(Ctxt.Arch.Ptrsize)
-	}
+	nod.Xoffset = fp.Width + Ctxt.FixedFrameSize()
 	nod.Type = fp.Type
 	Cgen_as(res, &nod)
 }
@@ -2597,10 +2567,7 @@ func cgen_aret(n *Node, res *Node) {
 	nod1.Op = OINDREG
 	nod1.Reg = int16(Thearch.REGSP)
 	nod1.Addable = true
-	nod1.Xoffset = fp.Width
-	if HasLinkRegister() {
-		nod1.Xoffset += int64(Ctxt.Arch.Ptrsize)
-	}
+	nod1.Xoffset = fp.Width + Ctxt.FixedFrameSize()
 	nod1.Type = fp.Type
 
 	if res.Op != OREGISTER {
@@ -2858,10 +2825,7 @@ func cgen_append(n, res *Node) {
 	arg.Op = OINDREG
 	arg.Reg = int16(Thearch.REGSP)
 	arg.Addable = true
-	arg.Xoffset = 0
-	if HasLinkRegister() {
-		arg.Xoffset = int64(Ctxt.Arch.Ptrsize)
-	}
+	arg.Xoffset = Ctxt.FixedFrameSize()
 	arg.Type = Ptrto(Types[TUINT8])
 	Cgen(typename(res.Type), &arg)
 	arg.Xoffset += int64(Widthptr)

src/cmd/compile/internal/gc/gsubr.go

@@ -568,9 +568,7 @@ fp:
 		n.Op = OINDREG
 
 		n.Reg = int16(Thearch.REGSP)
-		if HasLinkRegister() {
-			n.Xoffset += int64(Ctxt.Arch.Ptrsize)
-		}
+		n.Xoffset += Ctxt.FixedFrameSize()
 
 	case 1: // input arg
 		n.Class = PPARAM

src/cmd/compile/internal/ppc64/ggen.go

@@ -69,10 +69,10 @@ func zerorange(p *obj.Prog, frame int64, lo int64, hi int64) *obj.Prog {
 	}
 	if cnt < int64(4*gc.Widthptr) {
 		for i := int64(0); i < cnt; i += int64(gc.Widthptr) {
-			p = appendpp(p, ppc64.AMOVD, obj.TYPE_REG, ppc64.REGZERO, 0, obj.TYPE_MEM, ppc64.REGSP, 8+frame+lo+i)
+			p = appendpp(p, ppc64.AMOVD, obj.TYPE_REG, ppc64.REGZERO, 0, obj.TYPE_MEM, ppc64.REGSP, gc.Ctxt.FixedFrameSize()+frame+lo+i)
 		}
 	} else if cnt <= int64(128*gc.Widthptr) {
-		p = appendpp(p, ppc64.AADD, obj.TYPE_CONST, 0, 8+frame+lo-8, obj.TYPE_REG, ppc64.REGRT1, 0)
+		p = appendpp(p, ppc64.AADD, obj.TYPE_CONST, 0, gc.Ctxt.FixedFrameSize()+frame+lo-8, obj.TYPE_REG, ppc64.REGRT1, 0)
 		p.Reg = ppc64.REGSP
 		p = appendpp(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_MEM, 0, 0)
 		f := gc.Sysfunc("duffzero")
@@ -80,7 +80,7 @@ func zerorange(p *obj.Prog, frame int64, lo int64, hi int64) *obj.Prog {
 		gc.Afunclit(&p.To, f)
 		p.To.Offset = 4 * (128 - cnt/int64(gc.Widthptr))
 	} else {
-		p = appendpp(p, ppc64.AMOVD, obj.TYPE_CONST, 0, 8+frame+lo-8, obj.TYPE_REG, ppc64.REGTMP, 0)
+		p = appendpp(p, ppc64.AMOVD, obj.TYPE_CONST, 0, gc.Ctxt.FixedFrameSize()+frame+lo-8, obj.TYPE_REG, ppc64.REGTMP, 0)
 		p = appendpp(p, ppc64.AADD, obj.TYPE_REG, ppc64.REGTMP, 0, obj.TYPE_REG, ppc64.REGRT1, 0)
 		p.Reg = ppc64.REGSP
 		p = appendpp(p, ppc64.AMOVD, obj.TYPE_CONST, 0, cnt, obj.TYPE_REG, ppc64.REGTMP, 0)

src/cmd/internal/obj/link.go

@@ -523,6 +523,19 @@ type Link struct {
 	Etextp             *LSym
 }
 
+// The smallest possible offset from the hardware stack pointer to a local
+// variable on the stack. Architectures that use a link register save its value
+// on the stack in the function prologue and so always have a pointer between
+// the hardware stack pointer and the local variable area.
+func (ctxt *Link) FixedFrameSize() int64 {
+	switch ctxt.Arch.Thechar {
+	case '6', '8':
+		return 0
+	default:
+		return int64(ctxt.Arch.Ptrsize)
+	}
+}
+
 type SymVer struct {
 	Name    string
 	Version int // TODO: make int16 to match LSym.Version?

src/cmd/internal/obj/ppc64/asm9.go

@@ -595,7 +595,7 @@ func aclass(ctxt *obj.Link, a *obj.Addr) int {
 			return C_LAUTO
 
 		case obj.NAME_PARAM:
-			ctxt.Instoffset = int64(ctxt.Autosize) + a.Offset + 8
+			ctxt.Instoffset = int64(ctxt.Autosize) + a.Offset + ctxt.FixedFrameSize()
 			if ctxt.Instoffset >= -BIG && ctxt.Instoffset < BIG {
 				return C_SAUTO
 			}
@@ -658,7 +658,7 @@ func aclass(ctxt *obj.Link, a *obj.Addr) int {
 			return C_LACON
 
 		case obj.NAME_PARAM:
-			ctxt.Instoffset = int64(ctxt.Autosize) + a.Offset + 8
+			ctxt.Instoffset = int64(ctxt.Autosize) + a.Offset + ctxt.FixedFrameSize()
 			if ctxt.Instoffset >= -BIG && ctxt.Instoffset < BIG {
 				return C_SACON
 			}

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

@@ -337,7 +337,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 			if p.From3.Offset&obj.NOFRAME == 0 {
 				// If there is a stack frame at all, it includes
 				// space to save the LR.
-				autosize += 8
+				autosize += int32(ctxt.FixedFrameSize())
 			}
 
 			p.To.Offset = int64(autosize)
@@ -445,7 +445,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 				q = obj.Appendp(ctxt, q)
 				q.As = AADD
 				q.From.Type = obj.TYPE_CONST
-				q.From.Offset = int64(autosize) + 8
+				q.From.Offset = int64(autosize) + ctxt.FixedFrameSize()
 				q.Reg = REGSP
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R5
@@ -465,7 +465,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 				q = obj.Appendp(ctxt, q)
 				q.As = AADD
 				q.From.Type = obj.TYPE_CONST
-				q.From.Offset = 8
+				q.From.Offset = ctxt.FixedFrameSize()
 				q.Reg = REGSP
 				q.To.Type = obj.TYPE_REG
 				q.To.Reg = REG_R6