Re: [Qemu-devel] [PATCH 4/5] tcg: Optimize movcond for constant comparisons

[Aurelien Jarno]

On Tue, Sep 18, 2012 at 11:11:48PM +0200, Aurelien Jarno wrote:
> On Tue, Sep 18, 2012 at 07:23:59AM -0700, Richard Henderson wrote:
> > Signed-off-by: Richard Henderson <address@hidden>
> > ---
> >  tcg/optimize.c | 29 +++++++++++++++++++++++++++++
> >  1 file changed, 29 insertions(+)
> > 
> > diff --git a/tcg/optimize.c b/tcg/optimize.c
> > index fba0ed9..5b0a8ce 100644
> > --- a/tcg/optimize.c
> > +++ b/tcg/optimize.c
> > @@ -397,6 +397,14 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
> > uint16_t *tcg_opc_ptr,
> >                  args[3] = tcg_swap_cond(args[3]);
> >              }
> >              break;
> > +        CASE_OP_32_64(movcond):
> > +            if (temps[args[1]].state == TCG_TEMP_CONST
> > +                && temps[args[2]].state != TCG_TEMP_CONST) {
> > +                tmp = args[1];
> > +                args[1] = args[2];
> > +                args[2] = tmp;
> > +                args[5] = tcg_swap_cond(args[5]);
> > +            }
> >          default:
> >              break;
> >          }
> > @@ -617,6 +625,27 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
> > uint16_t *tcg_opc_ptr,
> >              }
> >              args += 4;
> >              break;
> > +        CASE_OP_33_64(movcond):
> > +            if (temps[args[1]].state == TCG_TEMP_CONST
> > +                && temps[args[2]].state == TCG_TEMP_CONST) {
> > +                gen_opc_buf[op_index] = op_to_mov(op);
> > +                tmp = do_constant_folding_cond(op, temps[args[1]].val,
> > +                                               temps[args[2]].val, 
> > args[5]);
> > +                tcg_opt_gen_mov(s, gen_args, args[0], args[4-tmp],
> > +                                nb_temps, nb_globals);
> > +                gen_args += 2;
> > +            } else {
> > +                reset_temp(args[0], nb_temps, nb_globals);
> > +                gen_args[0] = args[0];
> > +                gen_args[1] = args[1];
> > +                gen_args[2] = args[2];
> > +                gen_args[3] = args[3];
> > +                gen_args[4] = args[4];
> > +                gen_args[5] = args[5];
> > +                gen_args += 6;
> > +            }
> > +            args += 6;
> > +            break;
> >          case INDEX_op_call:
> >              nb_call_args = (args[0] >> 16) + (args[0] & 0xffff);
> >              if (!(args[nb_call_args + 1] & (TCG_CALL_CONST | 
> > TCG_CALL_PURE))) {
> > -- 
> > 1.7.11.4
> > 
> 
> Reviewed-by: Aurelien Jarno <address@hidden>

Playing a bit more with this patch, I have found it fails when v1 or v2
or constants or copies. The additional patch below fixes the problem.


diff --git a/tcg/optimize.c b/tcg/optimize.c
index f95c511..b7e235e 100644
--- a/tcg/optimize.c
+++ b/tcg/optimize.c
@@ -641,12 +641,23 @@ static TCGArg *tcg_constant_folding(TCGContext *s, 
uint16_t *tcg_opc_ptr,
         CASE_OP_32_64(movcond):
             if (temps[args[1]].state == TCG_TEMP_CONST
                 && temps[args[2]].state == TCG_TEMP_CONST) {
-                gen_opc_buf[op_index] = op_to_mov(op);
                 tmp = do_constant_folding_cond(op, temps[args[1]].val,
                                                temps[args[2]].val, args[5]);
-                tcg_opt_gen_mov(gen_args, args[0], args[4-tmp],
-                                nb_temps, nb_globals);
-                gen_args += 2;
+                if ((temps[args[4-tmp]].state == TCG_TEMP_COPY
+                    && temps[args[4-tmp]].val == args[0])
+                    || args[0] == args[4-tmp]) {
+                    gen_opc_buf[op_index] = INDEX_op_nop;
+                } else if (tmp && temps[args[4-tmp]].state == TCG_TEMP_CONST) {
+                    gen_opc_buf[op_index] = op_to_movi(op);
+                    tcg_opt_gen_movi(gen_args, args[0], temps[args[4-tmp]].val,
+                                     nb_temps, nb_globals);
+                    gen_args += 2;
+                } else {
+                    gen_opc_buf[op_index] = op_to_mov(op);
+                    tcg_opt_gen_mov(gen_args, args[0], args[4-tmp],
+                                    nb_temps, nb_globals);
+                    gen_args += 2;
+                }
             } else {
                 reset_temp(args[0], nb_temps, nb_globals);
                 gen_args[0] = args[0];

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net