4 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/dev-options.rst b/Documentation/dev-options.rst
index bf2d49a7..f6bfa79f 100644
--- a/Documentation/dev-options.rst
+++ b/Documentation/dev-options.rst
@@ -47,3 +47,7 @@ OPTIONS
 .. option:: -ventry
 
   Dump the IR after all optimization passes.
+
+.. option:: -vpostorder
+
+  Dump the reverse postorder traversal of the CFG.
diff --git a/flowgraph.c b/flowgraph.c
index 89897fa4..40a75e82 100644
--- a/flowgraph.c
+++ b/flowgraph.c
@@ -8,6 +8,7 @@
 #include "flowgraph.h"
 #include "linearize.h"
 #include "flow.h"			// for bb_generation
+#include <stdio.h>
 
 
 struct cfg_info {
@@ -41,6 +42,16 @@ static void reverse_bbs(struct basic_block_list **dst, struct basic_block_list *
 	} END_FOR_EACH_PTR_REVERSE(bb);
 }
 
+static void debug_postorder(struct entrypoint *ep)
+{
+	struct basic_block *bb;
+
+	printf("%s's reverse postorder:\n", show_ident(ep->name->ident));
+	FOR_EACH_PTR(ep->bbs, bb) {
+		printf("\t.L%u: %u\n", bb->nr, bb->postorder_nr);
+	} END_FOR_EACH_PTR(bb);
+}
+
 //
 // cfg_postorder - Set the BB's reverse postorder links
 //
@@ -61,5 +72,7 @@ int cfg_postorder(struct entrypoint *ep)
 	ep->bbs = NULL;
 	reverse_bbs(&ep->bbs, info.list);
 	free_ptr_list(&info.list);
+	if (dbg_postorder)
+		debug_postorder(ep);
 	return info.nr;
 }
diff --git a/lib.c b/lib.c
index 308f8f69..a13f0e1a 100644
--- a/lib.c
+++ b/lib.c
@@ -289,6 +289,7 @@ int dbg_compound = 0;
 int dbg_dead = 0;
 int dbg_entry = 0;
 int dbg_ir = 0;
+int dbg_postorder = 0;
 
 unsigned long fdump_ir;
 int fmem_report = 0;
@@ -768,6 +769,7 @@ static struct flag debugs[] = {
 	{ "dead", &dbg_dead},
 	{ "entry", &dbg_entry},
 	{ "ir", &dbg_ir},
+	{ "postorder", &dbg_postorder},
 };
 
 
diff --git a/lib.h b/lib.h
index b0453bb6..a3f29609 100644
--- a/lib.h
+++ b/lib.h
@@ -178,6 +178,7 @@ extern int dbg_compound;
 extern int dbg_dead;
 extern int dbg_entry;
 extern int dbg_ir;
+extern int dbg_postorder;
 
 extern unsigned int fmax_warnings;
 extern int fmem_report;