[dev.link] cmd/link: remove Unit field from sym.Symbol

Remove sym.Symbol 'Unit' field, replacing accesses to the field with
calls into the loader instead.

Change-Id: Ia1abd4c3d93036705dd624a49cb3d9cbe6a5188b
Reviewed-on: https://go-review.googlesource.com/c/go/+/230307
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

src/cmd/link/internal/ld/data2.go

@@ -324,7 +324,8 @@ func relocsym2(target *Target, ldr *loader.Loader, err *ErrorReporter, syms *Arc
 		case objabi.R_ADDRCUOFF:
 			// debug_range and debug_loc elements use this relocation type to get an
 			// offset from the start of the compile unit.
-			o = Symaddr(r.Sym) + r.Add - Symaddr(ldr.Syms[r.Sym.Unit.Textp2[0]])
+			u := ldr.SymUnit(loader.Sym(r.Sym.SymIdx))
+			o = Symaddr(r.Sym) + r.Add - Symaddr(ldr.Syms[u.Textp2[0]])
 
 			// r->sym can be null when CALL $(constant) is transformed from absolute PC to relative PC call.
 		case objabi.R_GOTPCREL:
@@ -482,4 +483,3 @@ func relocsym2(target *Target, ldr *loader.Loader, err *ErrorReporter, syms *Arc
 		}
 	}
 }
-

src/cmd/link/internal/loader/loader.go

@@ -2307,7 +2307,6 @@ func (l *Loader) addNewSym(i Sym, name string, ver int, unit *sym.CompilationUni
 		t = s.Type
 	}
 	s.Type = t
-	s.Unit = unit
 	l.growSyms(int(i))
 	l.installSym(i, s)
 	return s

src/cmd/link/internal/sym/sizeof_test.go

@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Symbol{}, 96, 152},
+		{Symbol{}, 92, 144},
 	}
 
 	for _, tt := range tests {

src/cmd/link/internal/sym/symbol.go

@@ -30,7 +30,6 @@ type Symbol struct {
 	SymIdx      LoaderSym
 	auxinfo     *AuxSymbol
 	Sect        *Section
-	Unit        *CompilationUnit
 	// P contains the raw symbol data.
 	P []byte
 	R []Reloc