Teach the loader to pre-compute the hash value for single-key lookups

Let the loader pre-compute the hash value when a single, literal key
is matched as in:

  #{<<"some_key">>:=V} = Map

In my measurements, this optimization resulted in a 30 percent
speedup for short binary keys.

Unfortunately, this optimizization makes no difference for small
maps with less than 32 keys, since the hash value is not used.
Still, there are the following use cases:

* A map used instead of a record with more than 32 entries. I have
seen some applications with huge records.

* Lookup in JSON dictionaries represented as maps.
The hash value will only be used when the map is a hash map
(currently, that means at least 32 entries).

1 files changed, 12 insertions, 14 deletions

diff --git a/erts/emulator/beam/ops.tab b/erts/emulator/beam/ops.tab
index 23f5b75b7a..456f879ab5 100644
--- a/erts/emulator/beam/ops.tab
+++ b/erts/emulator/beam/ops.tab
@@ -1512,8 +1512,6 @@ has_map_fields Fail Src Size Rest=* => \
 
 ## Transform get_map_elements(s) #{ K1 := V1, K2 := V2 }
 
-get_map_element/4
-
 get_map_elements Fail Src=rxy Size=u==2 Rest=* => \
     gen_get_map_element(Fail, Src, Size, Rest)
 get_map_elements Fail Src Size Rest=* | map_key_sort(Size, Rest) => \
@@ -1521,21 +1519,21 @@ get_map_elements Fail Src Size Rest=* | map_key_sort(Size, Rest) => \
 
 i_get_map_elements f s I
 
-get_map_element Fail Src=rxy Key=cx Dst => i_get_map_element Fail Src Key Dst
-get_map_element Fail Src=rxy Key=ry Dst => \
+i_get_map_element Fail Src=rxy Key=ry Dst => \
     move Key x | i_get_map_element Fail Src x Dst
-get_map_element Fail Src Key Dst => jump Fail
+
+%macro: i_get_map_element_hash GetMapElementHash -fail_action
+i_get_map_element_hash f r c I r
+i_get_map_element_hash f x c I r
+i_get_map_element_hash f y c I r
+i_get_map_element_hash f r c I x
+i_get_map_element_hash f x c I x
+i_get_map_element_hash f y c I x
+i_get_map_element_hash f r c I y
+i_get_map_element_hash f x c I y
+i_get_map_element_hash f y c I y
 
 %macro: i_get_map_element GetMapElement -fail_action
-i_get_map_element f r c r
-i_get_map_element f x c r
-i_get_map_element f y c r
-i_get_map_element f r c x
-i_get_map_element f x c x
-i_get_map_element f y c x
-i_get_map_element f r c y
-i_get_map_element f x c y
-i_get_map_element f y c y
 i_get_map_element f r x r
 i_get_map_element f x x r
 i_get_map_element f y x r