[M3devel] yet another proposed fix.. careful insertion of one instance of CG.Force() in CastExpr.m3

[Tony Hosking]

I wonder if we should be forcing all D_to_S?  Is it really only floats that cause this problem?  Why would that be the case?

On 6 Jul 2010, at 08:28, Jay K wrote:

> 
> Ok, this is interesting. I think. Finally.
> I need to test more, but it is looking very promising. I think you'll like it (Tony).
> I still don't understand all the flow around the front end. I had to try out some guesses.
> It certainly appears that m3front/src/misc/CG.m3 is in the business of optimizations.
> This change might actually be too conservative.
> It defeats optimization in CG.m3. It limits it to D_to_S when one type is float and the other isn't. 
>  I guess S (struct) can't really be float.
> 
> 
> The assertion failure in gcc btw, was gcc_assert( something_is_float == other_is_float).
> So the conservativeness is somewhat sensible.
> Limiting it to D_to_S, though, unclear.
> 
> 
> The change is just inserting CG.Force().
> 
> 
> OK? (Let me test a bit more -- build the entire tree.)
> 
> This appears to let me leave "ter" on.
> I can try leaving other optimizations on.
> 
> 
> Index: exprs/CastExpr.m3
> ===================================================================
> RCS file: /usr/cvs/cm3/m3-sys/m3front/src/exprs/CastExpr.m3,v
> retrieving revision 1.9
> diff -u -r1.9 CastExpr.m3
> --- exprs/CastExpr.m3    5 Jul 2010 11:28:32 -0000    1.9
> +++ exprs/CastExpr.m3    6 Jul 2010 12:23:14 -0000
> @@ -10,6 +10,7 @@
>  
>  IMPORT M3Buf, CG, Expr, ExprRep, Type, Error, OpenArrayType;
>  IMPORT M3, M3ID, M3RT, Target, TInt;
> +FROM Target IMPORT FloatType;
>  
>  TYPE
>    Kind = {
> @@ -394,7 +395,7 @@
>      u  := Expr.TypeOf (e);
>      t  := p.tipe;
>      sz, t_align, u_align, z_align: INTEGER;
> -    u_cg: CG.Type;
> +    u_cg, t_cg: CG.Type;
>      u_info, t_info: Type.Info;
>    BEGIN
>      u := Type.CheckInfo (u, u_info);
> @@ -403,6 +404,7 @@
>      u_align := u_info.alignment;
>      z_align := MAX (t_align, u_align);
>      u_cg := u_info.stk_type;
> +    t_cg := t_info.stk_type;
>      sz := u_info.size;
>      Type.Compile (t);
>      Type.Compile (u);
> @@ -416,6 +418,15 @@
>        Kind.V_to_V =>
>          Expr.CompileLValue (p.expr, traced);
>          CG.Boost_alignment (t_align);
> +(* Inhibit some optimization that causes compilation to fail. e.g. m3core:
> +../src/float/IEEE/RealFloat.m3: In function 'RealFloat__CopySign':
> +../src/float/IEEE/RealFloat.m3:96: internal compiler error: in convert_move, at expr.c:371
> +../src/float/IEEE/LongFloat.m3: In function 'LongFloat__CopySign':
> +../src/float/IEEE/LongFloat.m3:116: internal compiler error: in convert_move, at expr.c:371
> +*)
> +        IF p.kind = Kind.D_to_S AND FloatType[u_cg] # FloatType[t_cg] THEN
> +          CG.Force ();
> +        END;
>  
>      | Kind.D_to_A,
>        Kind.S_to_A,
> 
> 
> 
> (577) begin_procedure
>   procedure LongFloat__CopySign
>  LongFloat__CopySign(578) set_source_line
>   source line  117
> (579) load
>   type:lreal
>   type:lreal
>   m3cg_load (M3_CtKayy_x): offset 0x0, convert lreal -> lreal
> (580) store
>   type:lreal
>   type:lreal
>   store (M3_CtKayy_res) offset:0x0 src_t:lreal dst_t:lreal
> (581) set_source_line
>   source line  119
> 
> 
> now notice we have use of load_address and load_indirect here, where before we had no address and load (direct) 
> 
> 
> (582) load_address
>   load address (M3_CtKayy_res) offset 0x0
> (583) load_address
>   load address (M3_CtKayy_y) offset 0x0
> (584) load_indirect
>   type:word8
>   type:int64
>   load address offset:0x38 src_t:word8 dst_t:int64
> (585) extract_mn
>   type:int64
>  extract_mn offset:7 count:1 sign_extend:0
> (586) swap
>   type:addr
>   type:int64
> (587) declare_temp
>   type:addr
>   temp var type:addr size:0x40 alignment:0x40
> (588) store
>   type:addr
>   type:addr
>   store (noname) offset:0x0 src_t:addr dst_t:addr
> (589) load
>   type:addr
>   type:addr
>   m3cg_load (noname): offset 0x0, convert addr -> addr
> (590) load_indirect
>   type:word8
>   type:int64
>   load address offset:0x38 src_t:word8 dst_t:int64
> (591) swap
>   type:int64
>   type:word8
> (592) insert_mn
>   type:int64
>  insert_mn offset:7 count:1
> (593) load
>   type:addr
>   type:addr
>   m3cg_load (noname): offset 0x0, convert addr -> addr
> (594) swap
>   type:word8
>   type:addr
> (595) store_indirect
>   type:int64
>   type:word8
>   store indirect offset:0x38 src_t:int64 dst_t:word8
> (596) set_source_line
>   source line  120
> (597) load
>   type:lreal
>   type:lreal
>   m3cg_load (M3_CtKayy_res): offset 0x0, convert lreal -> lreal
> (598) exit_proc
>   type:lreal
> (599) free_temp
> (600) end_procedure
>   procedure LongFloat__CopySign
> 
> 
> 
>  - Jay
> 
>