beam_type: Convert integer to float at compile time

In code such as:

   X / 2

the following code would be output from beam_type for the division:

    {fconv,{x,0},{fr,0}}.
    {fconv,{integer,2},{fr,1}}.
    fclearerror.
    {bif,fdiv,{f,0},[{fr,0},{fr,1}],{fr,0}}.

That is, the integer 2 would be converted to the float 2.0 at
run-time by "{fconv,{integer,2},{fr,1}}". Make sure that we do
the conversion at compile time.

Noticed-by: Richard O'Keefe

1 files changed, 19 insertions, 4 deletions

diff --git a/lib/compiler/src/beam_type.erl b/lib/compiler/src/beam_type.erl
index 7392f99fb6..372923a5cf 100644
--- a/lib/compiler/src/beam_type.erl
+++ b/lib/compiler/src/beam_type.erl
@@ -142,9 +142,11 @@ simplify_float(Is0, Ts0) ->
 	throw:not_possible -> not_possible
     end.
 
-simplify_float_1([{set,[D0],[A],{alloc,_,{gc_bif,'-',{f,0}}}}=I|Is]=Is0, Ts0, Rs0, Acc0) ->
-    case tdb_find(A, Ts0) of
+simplify_float_1([{set,[D0],[A0],{alloc,_,{gc_bif,'-',{f,0}}}}=I|Is]=Is0,
+		 Ts0, Rs0, Acc0) ->
+    case tdb_find(A0, Ts0) of
 	float ->
+	    A = coerce_to_float(A0),
 	    {Rs1,Acc1} = load_reg(A, Ts0, Rs0, Acc0),
 	    {D,Rs} = find_dest(D0, Rs1),
 	    Areg = fetch_reg(A, Rs),
@@ -156,13 +158,16 @@ simplify_float_1([{set,[D0],[A],{alloc,_,{gc_bif,'-',{f,0}}}}=I|Is]=Is0, Ts0, Rs
 	    {Rs,Acc} = flush(Rs0, Is0, Acc0),
 	    simplify_float_1(Is, Ts, Rs, [I|checkerror(Acc)])
     end;
-simplify_float_1([{set,[D0],[A,B],{alloc,_,{gc_bif,Op0,{f,0}}}}=I|Is]=Is0, Ts0, Rs0, Acc0) ->
-    case float_op(Op0, A, B, Ts0) of
+simplify_float_1([{set,[D0],[A0,B0],{alloc,_,{gc_bif,Op0,{f,0}}}}=I|Is]=Is0,
+		 Ts0, Rs0, Acc0) ->
+    case float_op(Op0, A0, B0, Ts0) of
 	no ->
 	    Ts = update(I, Ts0),
 	    {Rs,Acc} = flush(Rs0, Is0, Acc0),
 	    simplify_float_1(Is, Ts, Rs, [I|checkerror(Acc)]);
 	{yes,Op} ->
+	    A = coerce_to_float(A0),
+	    B = coerce_to_float(B0),
 	    {Rs1,Acc1} = load_reg(A, Ts0, Rs0, Acc0),
 	    {Rs2,Acc2} = load_reg(B, Ts0, Rs1, Acc1),
 	    {D,Rs} = find_dest(D0, Rs2),
@@ -187,6 +192,16 @@ simplify_float_1([], Ts, Rs, Acc0) ->
     Is = opt_fmoves(Is0, []),
     {Is,Ts}.
 
+coerce_to_float({integer,I}=Int) ->
+    try float(I) of
+	F ->
+	    {float,F}
+    catch _:_ ->
+	    %% Let the overflow happen at run-time.
+	    Int
+    end;
+coerce_to_float(Other) -> Other.
+
 opt_fmoves([{set,[{x,_}=R],[{fr,_}]=Src,fmove}=I1,
 	    {set,[_]=Dst,[{x,_}=R],move}=I2|Is], Acc) ->
     case beam_utils:is_killed_block(R, Is) of