cmd/compile, cmd/link: more efficient typelink generation

Instead of generating typelink symbols in the compiler
mark types that should have typelinks with a flag.
The linker detects this flag and adds the marked types
to the typelink table.

name            old s/op    new s/op    delta
LinkCmdCompile   0.27 ± 6%   0.25 ± 6%  -6.93%    (p=0.000 n=97+98)
LinkCmdGo        0.30 ± 5%   0.29 ±10%  -4.22%    (p=0.000 n=97+99)

name            old MaxRSS  new MaxRSS  delta
LinkCmdCompile   112k ± 3%   106k ± 2%  -4.85%  (p=0.000 n=100+100)
LinkCmdGo        107k ± 3%   103k ± 3%  -3.00%  (p=0.000 n=100+100)

Change-Id: Ic95dd4b0101e90c1fa262c9c6c03a2028d6b3623
Reviewed-on: https://go-review.googlesource.com/31772
Run-TryBot: Shahar Kohanim <skohanim@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index 696a55849c..7ecc5b1ec2 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -110,11 +110,10 @@ func deadcode(ctxt *Link) {
 	}
 
 	if Buildmode != BuildmodeShared {
-		// Keep a typelink or itablink if the symbol it points at is being kept.
-		// (When BuildmodeShared, always keep typelinks and itablinks.)
+		// Keep a itablink if the symbol it points at is being kept.
+		// (When BuildmodeShared, always keep itablinks.)
 		for _, s := range ctxt.Syms.Allsym {
-			if strings.HasPrefix(s.Name, "go.typelink.") ||
-				strings.HasPrefix(s.Name, "go.itablink.") {
+			if strings.HasPrefix(s.Name, "go.itablink.") {
 				s.Attr.Set(AttrReachable, len(s.R) == 1 && s.R[0].Sym.Attr.Reachable())
 			}
 		}