Re: [Qemu-devel] [PATCH v2 07/29] tcg: Support cross-class moves without instruction support

[Alex Bennée]

Richard Henderson <address@hidden> writes:

> PowerPC Altivec does not support direct moves between vector registers
> and general registers.  So when tcg_out_mov fails, we can use the
> backing memory for the temporary to perform the move.

I couldn't see where tcg_out_mov fails in this way for ppc, it is still
abort or pass:

static bool tcg_out_mov(TCGContext *s, TCGType type, TCGReg ret, TCGReg arg)
{
    tcg_debug_assert(TCG_TARGET_REG_BITS == 64 || type == TCG_TYPE_I32);
    if (ret != arg) {
        tcg_out32(s, OR | SAB(arg, ret, arg));
    }
    return true;
}

did a patch get missed somewhere?



>
> Acked-by: David Hildenbrand <address@hidden>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/tcg.c | 31 ++++++++++++++++++++++++++++---
>  1 file changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/tcg/tcg.c b/tcg/tcg.c
> index 8ed7cb8654..68d86361e2 100644
> --- a/tcg/tcg.c
> +++ b/tcg/tcg.c
> @@ -3368,7 +3368,20 @@ static void tcg_reg_alloc_mov(TCGContext *s, const 
> TCGOp *op)
>                                           ots->indirect_base);
>              }
>              if (!tcg_out_mov(s, otype, ots->reg, ts->reg)) {
> -                abort();
> +                /*
> +                 * Cross register class move not supported.
> +                 * Store the source register into the destination slot
> +                 * and leave the destination temp as TEMP_VAL_MEM.
> +                 */
> +                assert(!ots->fixed_reg);
> +                if (!ts->mem_allocated) {
> +                    temp_allocate_frame(s, ots);
> +                }
> +                tcg_out_st(s, ts->type, ts->reg,
> +                           ots->mem_base->reg, ots->mem_offset);
> +                ots->mem_coherent = 1;
> +                temp_free_or_dead(s, ots, -1);
> +                return;
>              }
>          }
>          ots->val_type = TEMP_VAL_REG;
> @@ -3470,7 +3483,13 @@ static void tcg_reg_alloc_op(TCGContext *s, const 
> TCGOp *op)
>              reg = tcg_reg_alloc(s, arg_ct->u.regs, i_allocated_regs,
>                                  o_preferred_regs, ts->indirect_base);
>              if (!tcg_out_mov(s, ts->type, reg, ts->reg)) {
> -                abort();
> +                /*
> +                 * Cross register class move not supported.  Sync the
> +                 * temp back to its slot and load from there.
> +                 */
> +                temp_sync(s, ts, i_allocated_regs, 0, 0);
> +                tcg_out_ld(s, ts->type, reg,
> +                           ts->mem_base->reg, ts->mem_offset);
>              }
>          }
>          new_args[i] = reg;
> @@ -3631,7 +3650,13 @@ static void tcg_reg_alloc_call(TCGContext *s, TCGOp 
> *op)
>                  if (ts->reg != reg) {
>                      tcg_reg_free(s, reg, allocated_regs);
>                      if (!tcg_out_mov(s, ts->type, reg, ts->reg)) {
> -                        abort();
> +                        /*
> +                         * Cross register class move not supported.  Sync the
> +                         * temp back to its slot and load from there.
> +                         */
> +                        temp_sync(s, ts, allocated_regs, 0, 0);
> +                        tcg_out_ld(s, ts->type, reg,
> +                                   ts->mem_base->reg, ts->mem_offset);
>                      }
>                  }
>              } else {


--
Alex Bennée