Revert "cmd/internal/obj: fix pc/sp information for prologue"

This seems to have broken arm64 in a mysterious way. Will try again later.

This reverts commit 0a3c991f.

Change-Id: Ic1b53413c4168977a27381d9cc6fb8d9d7cbb780
Reviewed-on: https://go-review.googlesource.com/12245Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/internal/obj/arm/obj5.go

@@ -804,12 +804,8 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
 	}
 
-	spfix := obj.Appendp(ctxt, last)
-	spfix.As = obj.ANOP
-	spfix.Spadj = -framesize
-
 	// MOVW	LR, R3
-	movw := obj.Appendp(ctxt, spfix)
+	movw := obj.Appendp(ctxt, last)
 	movw.As = AMOVW
 	movw.From.Type = obj.TYPE_REG
 	movw.From.Reg = REGLINK
@@ -837,10 +833,6 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 	b.To.Type = obj.TYPE_BRANCH
 	b.Pcond = ctxt.Cursym.Text.Link
 
-	spfix = obj.Appendp(ctxt, b)
-	spfix.As = obj.ANOP
-	spfix.Spadj = +framesize
-
 	return bls
 }
 

src/cmd/internal/obj/arm64/obj7.go

@@ -161,12 +161,8 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
 	}
 
-	spfix := obj.Appendp(ctxt, last)
-	spfix.As = obj.ANOP
-	spfix.Spadj = -framesize
-
 	// MOV	LR, R3
-	movlr := obj.Appendp(ctxt, spfix)
+	movlr := obj.Appendp(ctxt, last)
 	movlr.As = AMOVD
 	movlr.From.Type = obj.TYPE_REG
 	movlr.From.Reg = REGLINK
@@ -206,10 +202,6 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
 	jmp.To.Type = obj.TYPE_BRANCH
 	jmp.Pcond = ctxt.Cursym.Text.Link
 
-	spfix = obj.Appendp(ctxt, jmp)
-	spfix.As = obj.ANOP
-	spfix.Spadj = +framesize
-
 	// placeholder for bls's jump target
 	// p = obj.Appendp(ctxt, p)
 	// p.As = obj.ANOP

src/cmd/internal/obj/x86/obj6.go

@@ -975,12 +975,7 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32) *ob
 	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
 	}
 
-	// Explain to PC-line tables that there is no frame here.
-	spfix := obj.Appendp(ctxt, last)
-	spfix.As = obj.ANOP
-	spfix.Spadj = -framesize
-
-	call := obj.Appendp(ctxt, spfix)
+	call := obj.Appendp(ctxt, last)
 	call.Lineno = ctxt.Cursym.Text.Lineno
 	call.Mode = ctxt.Cursym.Text.Mode
 	call.As = obj.ACALL
@@ -999,10 +994,6 @@ func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32) *ob
 	jmp.To.Type = obj.TYPE_BRANCH
 	jmp.Pcond = ctxt.Cursym.Text.Link
 
-	spfix = obj.Appendp(ctxt, jmp)
-	spfix.As = obj.ANOP
-	spfix.Spadj = +framesize
-
 	jls.Pcond = call
 	if q1 != nil {
 		q1.Pcond = call