Rewrite BSM optimizations in the new SSA-based intermediate format

This commit improves the bit-syntax match optimization pass,
leveraging the new SSA intermediate format to perform much more
aggressive optimizations. Some highlights:

* Watch contexts can be reused even after being passed to a
  function or being used in a try block.
* Sub-binaries are no longer eagerly extracted, making it far
  easier to keep "happy paths" free from binary creation.
* Trivial wrapper functions no longer disable context reuse.

1 files changed, 9 insertions, 4 deletions

diff --git a/erts/emulator/beam/erl_bits.h b/erts/emulator/beam/erl_bits.h
index 7beef5cfda..50d353e1fa 100644
--- a/erts/emulator/beam/erl_bits.h
+++ b/erts/emulator/beam/erl_bits.h
@@ -73,12 +73,16 @@ struct erl_bits_state {
 typedef struct erl_bin_match_struct{
   Eterm thing_word;
   ErlBinMatchBuffer mb;		/* Present match buffer */
-  Eterm save_offset[1];		/* Saved offsets */
+  Eterm save_offset[1];         /* Saved offsets, only valid for contexts
+                                 * created through bs_start_match2. */
 } ErlBinMatchState;
 
-#define ERL_BIN_MATCHSTATE_SIZE(_Max) ((sizeof(ErlBinMatchState) + (_Max)*sizeof(Eterm))/sizeof(Eterm)) 
-#define HEADER_BIN_MATCHSTATE(_Max) _make_header(ERL_BIN_MATCHSTATE_SIZE((_Max))-1, _TAG_HEADER_BIN_MATCHSTATE)
-#define HEADER_NUM_SLOTS(hdr) (header_arity(hdr)-sizeof(ErlBinMatchState)/sizeof(Eterm)+1)
+#define ERL_BIN_MATCHSTATE_SIZE(_Max) \
+    ((offsetof(ErlBinMatchState, save_offset) + (_Max)*sizeof(Eterm))/sizeof(Eterm))
+#define HEADER_BIN_MATCHSTATE(_Max) \
+    _make_header(ERL_BIN_MATCHSTATE_SIZE((_Max)) - 1, _TAG_HEADER_BIN_MATCHSTATE)
+#define HEADER_NUM_SLOTS(hdr) \
+    (header_arity(hdr) - (offsetof(ErlBinMatchState, save_offset) / sizeof(Eterm)) + 1)
 
 #define make_matchstate(_Ms) make_boxed((Eterm*)(_Ms))  
 #define ms_matchbuffer(_Ms) &(((ErlBinMatchState*) boxed_val(_Ms))->mb)
@@ -144,6 +148,7 @@ void erts_bits_destroy_state(ERL_BITS_PROTO_0);
  */
 
 Eterm erts_bs_start_match_2(Process *p, Eterm Bin, Uint Max);
+ErlBinMatchState *erts_bs_start_match_3(Process *p, Eterm Bin);
 Eterm erts_bs_get_integer_2(Process *p, Uint num_bits, unsigned flags, ErlBinMatchBuffer* mb);
 Eterm erts_bs_get_binary_2(Process *p, Uint num_bits, unsigned flags, ErlBinMatchBuffer* mb);
 Eterm erts_bs_get_float_2(Process *p, Uint num_bits, unsigned flags, ErlBinMatchBuffer* mb);