cmd/link: generate DIE for types referenced only through dictionaries

Generate debug_info entries for types that are only referenced through
dictionaries.

Change-Id: Ic36c2e6d9588ec6746793bb213c2dc0e17a8a850
Reviewed-on: https://go-review.googlesource.com/c/go/+/350532
Run-TryBot: Alessandro Arzilli <alessandro.arzilli@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Trust: Dan Scales <danscales@google.com>
Trust: David Chase <drchase@google.com>

1 files changed, 21 insertions, 2 deletions

diff --git a/src/cmd/link/internal/ld/dwarf_test.go b/src/cmd/link/internal/ld/dwarf_test.go
index 3d112d97a4..db9002491e 100644
--- a/src/cmd/link/internal/ld/dwarf_test.go
+++ b/src/cmd/link/internal/ld/dwarf_test.go
@@ -1749,7 +1749,9 @@ func main() {
 }
 
 func TestDictIndex(t *testing.T) {
-	// Check that variables with a parametric type have a dictionary index attribute
+	// Check that variables with a parametric type have a dictionary index
+	// attribute and that types that are only referenced through dictionaries
+	// have DIEs.
 	testenv.MustHaveGoBuild(t)
 
 	if runtime.GOOS == "plan9" {
@@ -1765,6 +1767,8 @@ package main
 
 import "fmt"
 
+type CustomInt int
+
 func testfn[T any](arg T) {
 	var mapvar = make(map[int]T)
 	mapvar[0] = arg
@@ -1772,7 +1776,7 @@ func testfn[T any](arg T) {
 }
 
 func main() {
-	testfn("test")
+	testfn(CustomInt(3))
 }
 `
 
@@ -1829,4 +1833,19 @@ func main() {
 			t.Errorf("could not find DW_AT_go_dict_index attribute offset %#x (%T)", off, entry.Val(intdwarf.DW_AT_go_dict_index))
 		}
 	}
+
+	rdr.Seek(0)
+	ex := examiner{}
+	if err := ex.populate(rdr); err != nil {
+		t.Fatalf("error reading DWARF: %v", err)
+	}
+	for _, typeName := range []string{"main.CustomInt", "map[int]main.CustomInt"} {
+		dies := ex.Named(typeName)
+		if len(dies) != 1 {
+			t.Errorf("wanted 1 DIE named %s, found %v", typeName, len(dies))
+		}
+		if dies[0].Val(intdwarf.DW_AT_go_runtime_type).(uint64) == 0 {
+			t.Errorf("type %s does not have DW_AT_go_runtime_type", typeName)
+		}
+	}
 }