From 5836998a956966a5ecc6dddfc4f8b73fc3aa6f1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Mon, 18 Mar 2019 07:00:56 +0100
Subject: Optimize funs converted to literals

---
 erts/emulator/beam/beam_load.c |  6 +++++-
 erts/emulator/beam/ops.tab     | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

(limited to 'erts')

diff --git a/erts/emulator/beam/beam_load.c b/erts/emulator/beam/beam_load.c
index c2a54c85ce..21740caa2c 100644
--- a/erts/emulator/beam/beam_load.c
+++ b/erts/emulator/beam/beam_load.c
@@ -4352,7 +4352,11 @@ gen_make_fun2(LoaderState* stp, GenOpArg idx)
         funp->creator = erts_init_process_id;
         funp->arity = arity;
 
-        GENOP_NAME_ARITY(op, move, 2);
+        /*
+         * Use a move_fun/2 instruction to load the fun to enable
+         * further optimizations.
+         */
+        GENOP_NAME_ARITY(op, move_fun, 2);
         op->a[0].type = TAG_q;
         op->a[0].val = lit;
         op->a[1].type = TAG_x;
diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 46afeb51c9..485703101f 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1148,8 +1148,25 @@ call_fun Arity => i_call_fun Arity
 i_call_fun t
 i_call_fun_last t Q
 
+
+#
+# A fun with an empty environment can be converted to a literal.
+# As a further optimization, the we try to move the fun to its
+# final destination directly.
+
 make_fun2 OldIndex=u => gen_make_fun2(OldIndex)
 
+move_fun/2
+move_fun Fun X0 | move X0 Dst | move Src X0 => move Fun Dst | move Src X0
+move_fun Fun X0 | move A B | move X0 Dst | move Src X0 | \
+  independent_moves(Fun, X0, A, B) | distinct(Dst, A) => \
+    move Fun Dst | move A B | move Src X0
+move_fun Fun X0 | move X0 Dst | make_fun2 OldIndex | \
+  is_killed_by_make_fun(X0, OldIndex)=> \
+    move Fun Dst | make_fun2 OldIndex
+
+move_fun Fun Dst => move Fun Dst
+
 %cold
 i_make_fun W t
 %hot
-- 
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