v3_codegen: Reduce cost for fixing up bs_match_string instructions

Commit b76588fb5a introduced an optimization of the compile time of
huge functions with many bs_match_string instructions. The
optimization is done in two passes. The first pass coalesces adjacent
bs_match_string instructions. To avoid copying bitstrings multiple
times, the bitstrings in the instructions are combined in to a (deep)
list. The second pass goes through all instructions in the function
and combines the list of bitstrings to a single bitstring in all
bs_match_string instructions.

The second pass (fix_bs_match_string) is run on all instructions in
each function, even if there are no bs_match_instructions in the
function. While fix_bs_match_string is not a bottleneck (it is a
linear pass), its execution time is noticeable when profiling some
modules.

Move the execution of the second pass to the select_binary()
function so that it will only be executed for instructions that
do binary matching. Also take the opportunity to optimize away
uses of bs_restore2 that occour directly after a bs_save2. That
optimimization is currently done in beam_block, but it can be
done essentially for free in the same pass that fixes up
bs_match_string instructions.

1 files changed, 0 insertions, 9 deletions

diff --git a/lib/compiler/src/beam_block.erl b/lib/compiler/src/beam_block.erl
index 5216f39296..e2639e9cac 100644
--- a/lib/compiler/src/beam_block.erl
+++ b/lib/compiler/src/beam_block.erl
@@ -61,15 +61,6 @@ blockify(Is) ->
 blockify([{loop_rec,{f,Fail},{x,0}},{loop_rec_end,_Lbl},{label,Fail}|Is], Acc) ->
     %% Useless instruction sequence.
     blockify(Is, Acc);
-
-%% New bit syntax matching.
-blockify([{bs_save2,R,Point}=I,{bs_restore2,R,Point}|Is], Acc) ->
-    blockify([I|Is], Acc);
-blockify([{bs_save2,R,Point}=I,{test,is_eq_exact,_,_}=Test,
-	  {bs_restore2,R,Point}|Is], Acc) ->
-    blockify([I,Test|Is], Acc);
-
-%% Do other peep-hole optimizations.
 blockify([{test,is_atom,{f,Fail},[Reg]}=I|
 	  [{select,select_val,Reg,{f,Fail},
 	    [{atom,false},{f,_}=BrFalse,