4 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/dev-options.rst b/Documentation/dev-options.rst
index f6bfa79f..04fb651f 100644
--- a/Documentation/dev-options.rst
+++ b/Documentation/dev-options.rst
@@ -44,6 +44,10 @@ OPTIONS
 
   Add ``OP_DEATHNOTE`` annotations to dead pseudos.
 
+.. option:: -vdomtree
+
+  Dump the dominance tree after its calculation.
+
 .. option:: -ventry
 
   Dump the IR after all optimization passes.
diff --git a/flowgraph.c b/flowgraph.c
index d5551908..b2d95893 100644
--- a/flowgraph.c
+++ b/flowgraph.c
@@ -102,6 +102,18 @@ static struct basic_block *intersect_dom(struct basic_block *doms[],
 	return b1;
 }
 
+static void debug_domtree(struct entrypoint *ep)
+{
+	struct basic_block *bb = ep->entry->bb;
+
+	printf("%s's idoms:\n", show_ident(ep->name->ident));
+	FOR_EACH_PTR(ep->bbs, bb) {
+		if (bb == ep->entry->bb)
+			continue;	// entry node has no idom
+		printf("\t%s	<- %s\n", show_label(bb), show_label(bb->idom));
+	} END_FOR_EACH_PTR(bb);
+}
+
 void domtree_build(struct entrypoint *ep)
 {
 	struct basic_block *entry = ep->entry->bb;
@@ -178,4 +190,6 @@ void domtree_build(struct entrypoint *ep)
 	ep->dom_levels = max_level + 1;
 
 	free(doms);
+	if (dbg_domtree)
+		debug_domtree(ep);
 }
diff --git a/lib.c b/lib.c
index a13f0e1a..1c556e22 100644
--- a/lib.c
+++ b/lib.c
@@ -287,6 +287,7 @@ int dump_macro_defs = 0;
 
 int dbg_compound = 0;
 int dbg_dead = 0;
+int dbg_domtree = 0;
 int dbg_entry = 0;
 int dbg_ir = 0;
 int dbg_postorder = 0;
@@ -767,6 +768,7 @@ static char **handle_switch_W(char *arg, char **next)
 static struct flag debugs[] = {
 	{ "compound", &dbg_compound},
 	{ "dead", &dbg_dead},
+	{ "domtree", &dbg_domtree},
 	{ "entry", &dbg_entry},
 	{ "ir", &dbg_ir},
 	{ "postorder", &dbg_postorder},
diff --git a/lib.h b/lib.h
index a3f29609..68369190 100644
--- a/lib.h
+++ b/lib.h
@@ -176,6 +176,7 @@ extern int dump_macro_defs;
 
 extern int dbg_compound;
 extern int dbg_dead;
+extern int dbg_domtree;
 extern int dbg_entry;
 extern int dbg_ir;
 extern int dbg_postorder;