From 9c852215c79ed6ec42c223463d4b5a0c221b4bf0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Wed, 16 Jan 2019 19:06:19 +0100
Subject: beam_ssa_type: Eliminate redundant 'succeeded' instructions

The beam_ssa_type pass would leave redundant 'succeeded' instructions,
and depend on the live optimization pass to remove them.

Update beam_ssa_type to remove redundant 'succeeded' instructions.
This will not improve the generated code, but will improve compilation
times since it eliminates instructions and variables.
---
 lib/compiler/src/beam_ssa_opt.erl  | 11 +++--------
 lib/compiler/src/beam_ssa_type.erl | 17 +++++++++++++++--
 2 files changed, 18 insertions(+), 10 deletions(-)

(limited to 'lib/compiler')

diff --git a/lib/compiler/src/beam_ssa_opt.erl b/lib/compiler/src/beam_ssa_opt.erl
index 6bba47b4ac..e23e62b5ad 100644
--- a/lib/compiler/src/beam_ssa_opt.erl
+++ b/lib/compiler/src/beam_ssa_opt.erl
@@ -856,14 +856,9 @@ live_opt_is([#b_set{op=succeeded,dst=SuccDst=SuccDstVar,
              #b_set{dst=Dst}=I|Is], Live0, Acc) ->
     case gb_sets:is_member(Dst, Live0) of
         true ->
-            case gb_sets:is_member(SuccDst, Live0) of
-                true ->
-                    Live1 = gb_sets:add(Dst, Live0),
-                    Live = gb_sets:delete_any(SuccDst, Live1),
-                    live_opt_is([I|Is], Live, [SuccI|Acc]);
-                false ->
-                    live_opt_is([I|Is], Live0, Acc)
-            end;
+            Live1 = gb_sets:add(Dst, Live0),
+            Live = gb_sets:delete_any(SuccDst, Live1),
+            live_opt_is([I|Is], Live, [SuccI|Acc]);
         false ->
             case live_opt_unused(I) of
                 {replace,NewI0} ->
diff --git a/lib/compiler/src/beam_ssa_type.erl b/lib/compiler/src/beam_ssa_type.erl
index ab5ea4b1a4..4ea3781783 100644
--- a/lib/compiler/src/beam_ssa_type.erl
+++ b/lib/compiler/src/beam_ssa_type.erl
@@ -139,6 +139,19 @@ opt_is([#b_set{op=phi,dst=Dst,args=Args0}=I0|Is],
             Ds = Ds0#{Dst=>I},
             opt_is(Is, Ts, Ds, Ls, Sub0, [I|Acc])
     end;
+opt_is([#b_set{op=succeeded,args=Args0,dst=Dst}=I],
+       Ts0, Ds0, Ls, Sub0, Acc) ->
+    Args = simplify_args(Args0, Sub0, Ts0),
+    Type = type(succeeded, Args, Ts0, Ds0),
+    case get_literal_from_type(Type) of
+        #b_literal{}=Lit ->
+            Sub = Sub0#{Dst=>Lit},
+            opt_is([], Ts0, Ds0, Ls, Sub, Acc);
+        none ->
+            Ts = update_types(I, Ts0, Ds0),
+            Ds = Ds0#{Dst=>I},
+            opt_is([], Ts, Ds, Ls, Sub0, [I|Acc])
+    end;
 opt_is([#b_set{args=Args0,dst=Dst}=I0|Is],
        Ts0, Ds0, Ls, Sub0, Acc) ->
     Args = simplify_args(Args0, Sub0, Ts0),
@@ -296,8 +309,6 @@ simplify(#b_set{op=put_tuple,args=Args}=I, _Ts) ->
         none -> I;
         List -> #b_literal{val=list_to_tuple(List)}
     end;
-simplify(#b_set{op=succeeded,args=[#b_literal{}]}, _Ts) ->
-    #b_literal{val=true};
 simplify(#b_set{op=wait_timeout,args=[#b_literal{val=infinity}]}=I, _Ts) ->
     I#b_set{op=wait,args=[]};
 simplify(I, _Ts) -> I.
@@ -627,6 +638,8 @@ type(succeeded, [#b_var{}=Src], Ts, Ds) ->
         #b_set{} ->
             t_boolean()
     end;
+type(succeeded, [#b_literal{}], _Ts, _Ds) ->
+    t_atom(true);
 type(_, _, _, _) -> any.
 
 arith_op_type(Args, Ts) ->
-- 
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