cmd/compile: don't emit autom's into object file

Don't write Autom records when writing a function to the object file;
we no longer need them in the linker for DWARF processing. So as to
keep the object file format unchanged, write out a zero-length list of
automs to the object, as opposed to removing all references.

Updates #34554.

Change-Id: I42a1d67207ea7114ae4f3a315cf37effba57f190
Reviewed-on: https://go-review.googlesource.com/c/go/+/197499
Reviewed-by: Jeremy Faller <jeremy@golang.org>

1 files changed, 2 insertions, 22 deletions

diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index 165e618d53..ab5627c0dd 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -31,7 +31,6 @@ type objWriter struct {
 	nData     int
 	nReloc    int
 	nPcdata   int
-	nAutom    int
 	nFuncdata int
 	nFile     int
 
@@ -60,7 +59,6 @@ func (w *objWriter) addLengths(s *LSym) {
 	w.nData += data
 	w.nPcdata += len(pc.Pcdata)
 
-	w.nAutom += len(s.Func.Autom)
 	w.nFuncdata += len(pc.Funcdataoff)
 	w.nFile += len(pc.File)
 }
@@ -69,7 +67,7 @@ func (w *objWriter) writeLengths() {
 	w.writeInt(int64(w.nData))
 	w.writeInt(int64(w.nReloc))
 	w.writeInt(int64(w.nPcdata))
-	w.writeInt(int64(w.nAutom))
+	w.writeInt(int64(0)) // TODO: remove at next object file rev
 	w.writeInt(int64(w.nFuncdata))
 	w.writeInt(int64(w.nFile))
 }
@@ -206,10 +204,6 @@ func (w *objWriter) writeRefs(s *LSym) {
 	}
 
 	if s.Type == objabi.STEXT {
-		for _, a := range s.Func.Autom {
-			w.writeRef(a.Asym, false)
-			w.writeRef(a.Gotype, false)
-		}
 		pc := &s.Func.Pcln
 		for _, d := range pc.Funcdata {
 			w.writeRef(d, false)
@@ -364,21 +358,7 @@ func (w *objWriter) writeSym(s *LSym) {
 		flags |= 1 << 4
 	}
 	w.writeInt(flags)
-	w.writeInt(int64(len(s.Func.Autom)))
-	for _, a := range s.Func.Autom {
-		w.writeRefIndex(a.Asym)
-		w.writeInt(int64(a.Aoffset))
-		if a.Name == NAME_AUTO {
-			w.writeInt(objabi.A_AUTO)
-		} else if a.Name == NAME_PARAM {
-			w.writeInt(objabi.A_PARAM)
-		} else if a.Name == NAME_DELETED_AUTO {
-			w.writeInt(objabi.A_DELETED_AUTO)
-		} else {
-			log.Fatalf("%s: invalid local variable type %d", s.Name, a.Name)
-		}
-		w.writeRefIndex(a.Gotype)
-	}
+	w.writeInt(int64(0)) // TODO: remove at next object file rev
 
 	pc := &s.Func.Pcln
 	w.writeInt(int64(len(pc.Pcsp.P)))