v3_kernel: Generate optimized code for guards

The compiler produces poor code for complex guard expressions with andalso/orelse.
Here is an example from the filename module:

-define(IS_DRIVELETTER(Letter),(((Letter >= $A) andalso (Letter =< $Z)) orelse
				((Letter >= $a) andalso (Letter =< $z)))).
skip_prefix(Name, false) ->
    Name;
skip_prefix([L, DrvSep|Name], DrvSep) when ?IS_DRIVELETTER(L) ->
    Name;
skip_prefix(Name, _) ->
    Name.

beam_bool fails to simplify the code for the guard, leaving several 'bif'
instructions:

{function, skip_prefix, 2, 49}.
  {label,48}.
    {line,[{location,"filename.erl",187}]}.
    {func_info,{atom,filename},{atom,skip_prefix},2}.
  {label,49}.
    {test,is_ne_exact,{f,52},[{x,1},{atom,false}]}.
    {test,is_nonempty_list,{f,52},[{x,0}]}.
    {get_list,{x,0},{x,2},{x,3}}.
    {test,is_nonempty_list,{f,52},[{x,3}]}.
    {get_list,{x,3},{x,4},{x,5}}.
    {bif,'=:=',{f,52},[{x,1},{x,4}],{x,6}}.
    {test,is_ge,{f,50},[{x,2},{integer,65}]}.
    {bif,'=<',{f,52},[{x,2},{integer,90}],{x,7}}.
    {test,is_eq_exact,{f,51},[{x,7},{atom,false}]}.
    {test,is_ge,{f,50},[{x,2},{integer,97}]}.
    {bif,'=<',{f,52},[{x,2},{integer,122}],{x,7}}.
    {jump,{f,51}}.
  {label,50}.
    {move,{atom,false},{x,7}}.
  {label,51}.
    {bif,'=:=',{f,52},[{x,7},{atom,true}],{x,7}}.
    {test,is_eq_exact,{f,52},[{x,6},{atom,true}]}.
    {test,is_eq_exact,{f,52},[{x,7},{atom,true}]}.
    {move,{x,5},{x,0}}.
    return.
  {label,52}.
    return.

We can add optimizations of guard tests to v3_kernel to achive a better result:

{function, skip_prefix, 2, 49}.
  {label,48}.
    {line,[{location,"filename.erl",187}]}.
    {func_info,{atom,filename},{atom,skip_prefix},2}.
  {label,49}.
    {test,is_ne_exact,{f,51},[{x,1},{atom,false}]}.
    {test,is_nonempty_list,{f,51},[{x,0}]}.
    {get_list,{x,0},{x,2},{x,3}}.
    {test,is_nonempty_list,{f,51},[{x,3}]}.
    {get_list,{x,3},{x,4},{x,5}}.
    {test,is_eq_exact,{f,51},[{x,1},{x,4}]}.
    {test,is_ge,{f,51},[{x,2},{integer,65}]}.
    {test,is_lt,{f,50},[{integer,90},{x,2}]}.
    {test,is_ge,{f,51},[{x,2},{integer,97}]}.
    {test,is_ge,{f,51},[{integer,122},{x,2}]}.
  {label,50}.
    {move,{x,5},{x,0}}.
    return.
  {label,51}.
    return.

Looking at the STDLIB application, there were 112 lines of BIF calls in guards
that beam_bool failed to convert to test instructions. This commit eliminates
all those BIF calls.

Here is how I counted the instructions:

$ PATH=$ERL_TOP/bin:$PATH erlc -I ../include -I ../../kernel/include -S *.erl
$ grep "bif,'[=<>]" *.S | grep -v f,0
dets.S:    {bif,'=:=',{f,547},[{x,4},{atom,read_write}],{x,4}}.
dets.S:    {bif,'=:=',{f,547},[{x,5},{atom,saved}],{x,5}}.
dets.S:    {bif,'=:=',{f,589},[{x,5},{atom,read}],{x,5}}.
.
.
.
$ grep "bif,'[=<>]" *.S | grep -v f,0 | wc
     112     224    6765
$

1 files changed, 17 insertions, 3 deletions

diff --git a/lib/compiler/src/v3_codegen.erl b/lib/compiler/src/v3_codegen.erl
index c2e0c2bd1a..3627cdb7cd 100644
--- a/lib/compiler/src/v3_codegen.erl
+++ b/lib/compiler/src/v3_codegen.erl
@@ -363,7 +363,7 @@ bsm_rename_ctx(#l{ke={match,Ms0,Rs}}=L, Old, New, InProt) ->
 bsm_rename_ctx(#l{ke={guard_match,Ms0,Rs}}=L, Old, New, InProt) ->
     Ms = bsm_rename_ctx(Ms0, Old, New, InProt),
     L#l{ke={guard_match,Ms,Rs}};
-bsm_rename_ctx(#l{ke={test,_,_}}=L, _, _, _) -> L;
+bsm_rename_ctx(#l{ke={test,_,_,_}}=L, _, _, _) -> L;
 bsm_rename_ctx(#l{ke={bif,_,_,_}}=L, _, _, _) -> L;
 bsm_rename_ctx(#l{ke={gc_bif,_,_,_}}=L, _, _, _) -> L;
 bsm_rename_ctx(#l{ke={set,_,_}}=L, _, _, _) -> L;
@@ -1051,8 +1051,15 @@ guard_cg(#l{ke={protected,Ts,Rs},i=I,vdb=Pdb}, Fail, _Vdb, Bef, St) ->
     protected_cg(Ts, Rs, Fail, I, Pdb, Bef, St);
 guard_cg(#l{ke={block,Ts},i=I,vdb=Bdb}, Fail, _Vdb, Bef, St) ->
     guard_cg_list(Ts, Fail, I, Bdb, Bef, St);
-guard_cg(#l{ke={test,Test,As},i=I,vdb=_Tdb}, Fail, Vdb, Bef, St) ->
-    test_cg(Test, As, Fail, I, Vdb, Bef, St);
+guard_cg(#l{ke={test,Test,As,Inverted},i=I,vdb=_Tdb}, Fail, Vdb, Bef, St0) ->
+    case Inverted of
+	false ->
+	    test_cg(Test, As, Fail, I, Vdb, Bef, St0);
+	true ->
+	    {Psucc,St1} = new_label(St0),
+	    {Is,Aft,St2} = test_cg(Test, As, Psucc, I, Vdb, Bef, St1),
+	    {Is++[{jump,{f,Fail}},{label,Psucc}],Aft,St2}
+    end;
 guard_cg(G, _Fail, Vdb, Bef, St) ->
     %%ok = io:fwrite("cg ~w: ~p~n", [?LINE,{G,Fail,Vdb,Bef}]),
     {Gis,Aft,St1} = cg(G, Vdb, Bef, St),
@@ -1103,6 +1110,13 @@ test_cg(is_map, [A], Fail, I, Vdb, Bef, St) ->
     Arg = cg_reg_arg_prefer_y(A, Bef),
     Aft = clear_dead(Bef, I, Vdb),
     {[{test,is_map,{f,Fail},[Arg]}],Aft,St};
+test_cg(is_boolean, [{atom,Val}], Fail, I, Vdb, Bef, St) ->
+    Aft = clear_dead(Bef, I, Vdb),
+    Is = case is_boolean(Val) of
+	     true -> [];
+	     false -> [{jump,{f,Fail}}]
+	 end,
+    {Is,Aft,St};
 test_cg(Test, As, Fail, I, Vdb, Bef, St) ->
     Args = cg_reg_args(As, Bef),
     Aft = clear_dead(Bef, I, Vdb),