cmd/link: tidy up rdsym

Use an early return. Check errors. Deduplicate.

Change-Id: Iabefd563b5ef82a16fab4791277630804fd09003
Reviewed-on: https://go-review.googlesource.com/20597
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/cmd/link/internal/ld/objfile.go b/src/cmd/link/internal/ld/objfile.go
index 29f629efdc232c34cda9c3429227f36fa0b34271..6e243052abd87aacc0b5b4fbd23b056b5f9af216 100644 (file)
--- a/src/cmd/link/internal/ld/objfile.go
+++ b/src/cmd/link/internal/ld/objfile.go
@@ -494,25 +494,31 @@ func rdsym(ctxt *Link, f *obj.Biobuf, pkg string) *LSym {
                v = ctxt.Version
        }
        s := Linklookup(ctxt, name, v)
+       if v != 0 {
+               return s
+       }
 
-       if v == 0 && s.Name[0] == '$' && s.Type == 0 {
-               if strings.HasPrefix(s.Name, "$f32.") {
-                       x, _ := strconv.ParseUint(s.Name[5:], 16, 32)
-                       i32 := int32(x)
-                       s.Type = obj.SRODATA
-                       s.Attr |= AttrLocal
-                       Adduint32(ctxt, s, uint32(i32))
-                       s.Attr.Set(AttrReachable, false)
-               } else if strings.HasPrefix(s.Name, "$f64.") || strings.HasPrefix(s.Name, "$i64.") {
-                       x, _ := strconv.ParseUint(s.Name[5:], 16, 64)
-                       i64 := int64(x)
-                       s.Type = obj.SRODATA
-                       s.Attr |= AttrLocal
-                       Adduint64(ctxt, s, uint64(i64))
-                       s.Attr.Set(AttrReachable, false)
+       if s.Name[0] == '$' && len(s.Name) > 5 && s.Type == 0 {
+               x, err := strconv.ParseUint(s.Name[5:], 16, 64)
+               if err != nil {
+                       log.Panicf("failed to parse $-symbol %s: %v", s.Name, err)
+               }
+               s.Type = obj.SRODATA
+               s.Attr |= AttrLocal
+               switch s.Name[:5] {
+               case "$f32.":
+                       if uint64(uint32(x)) != x {
+                               log.Panicf("$-symbol %s too large: %d", s.Name, x)
+                       }
+                       Adduint32(ctxt, s, uint32(x))
+               case "$f64.", "$i64.":
+                       Adduint64(ctxt, s, x)
+               default:
+                       log.Panicf("unrecognized $-symbol: %s", s.Name)
                }
+               s.Attr.Set(AttrReachable, false)
        }
-       if v == 0 && strings.HasPrefix(s.Name, "runtime.gcbits.") {
+       if strings.HasPrefix(s.Name, "runtime.gcbits.") {
                s.Attr |= AttrLocal
        }
        return s