gistfile1.txt

diff --git a/3rdparty/dyncall b/3rdparty/dyncall
--- a/3rdparty/dyncall
+++ b/3rdparty/dyncall
@@ -1 +1 @@
-Subproject commit 5c4e85c290756b84eb55c9ed97f550555bcdc29d
+Subproject commit 5c4e85c290756b84eb55c9ed97f550555bcdc29d-dirty
diff --git a/src/spesh/facts.c b/src/spesh/facts.c
index a5c4f2f..14f85b8 100644
--- a/src/spesh/facts.c
+++ b/src/spesh/facts.c
@@ -133,6 +133,9 @@ static void add_bb_facts(MVMThreadContext *tc, MVMSpeshGraph *g, MVMSpeshBB *bb)
                 (ins->info->operands[i] & MVM_operand_rw_mask) == MVM_operand_read_reg)
                 g->facts[ins->operands[i].reg.orig][ins->operands[i].reg.i].usages++;
 
+        if (ins->info->num_operands >= 1 && (ins->info->operands[0] & MWM_operand_rw_mask) == MVM_operand_write_reg)
+            g->facts[ins->operands[0].reg.orig][ins->operands[0].reg.i].origin = ins;
+
         /* Look for ops that are fact-interesting. */
         switch (ins->info->opcode) {
         case MVM_OP_inc_i:
diff --git a/src/spesh/facts.h b/src/spesh/facts.h
index 9bea593..ce8cd75 100644
--- a/src/spesh/facts.h
+++ b/src/spesh/facts.h
@@ -12,6 +12,9 @@ struct MVMSpeshFacts {
     /* Known type post-decontainerization, if any. */
     MVMObject *decont_type;
 
+    /* The instruction that's the origin of this register + version */
+    MVMSpeshIns *origin;
+
     /* Known value, if any. */
     union {
         MVMObject *o;