[PATCH] [llgo] debug: create replaceable type through DIBuilder

[Andrew Wilkins]

Hi pcc,

llgo was asserting in DebugInfo, which was interpreting
the temporary MDNodes we were creating as DIScopes instead
of DITypes (in DIScope::getRef).

This proposal changes llgo to use DIBuilder's
createReplaceableCompositeType method to create a DIType
that can be RAUW'd.

http://reviews.llvm.org/D7852

Files:
  debug/debug.go

Index: debug/debug.go
===================================================================
--- debug/debug.go
+++ debug/debug.go
@@ -340,18 +340,26 @@
 }
 
 func (d *DIBuilder) descriptorNamed(t *types.Named) llvm.Metadata {
-	// Create a placeholder for the named type, to terminate cycles.
-	placeholder := llvm.GlobalContext().TemporaryMDNode(nil)
-	d.types.Set(t, placeholder)
 	var diFile llvm.Metadata
 	var line int
 	if file := d.fset.File(t.Obj().Pos()); file != nil {
 		line = file.Line(t.Obj().Pos())
 		diFile = d.getFile(file)
 	}
+
+	// Create a placeholder for the named type, to terminate cycles.
+	name := t.Obj().Name()
+	placeholder := d.builder.CreateReplaceableCompositeType(d.scope(), llvm.DIReplaceableCompositeType{
+		Tag:  dwarf.TagStructType,
+		Name: name,
+		File: diFile,
+		Line: line,
+	})
+	d.types.Set(t, placeholder)
+
 	typedef := d.builder.CreateTypedef(llvm.DITypedef{
 		Type: d.DIType(t.Underlying()),
-		Name: t.Obj().Name(),
+		Name: name,
 		File: diFile,
 		Line: line,
 	})

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