Re: [PATCH 2/3] expmed: Fix possible use of NULL_RTX return value from emit_store_flag

[Richard Sandiford <richard.sandiford@arm.com>]

Jozef Lawrynowicz <jozef.l@mittosystems.com> writes:
> diff --git a/gcc/expmed.c b/gcc/expmed.c
> index e7c03fbf92c..d3a1735d39e 100644
> --- a/gcc/expmed.c
> +++ b/gcc/expmed.c
> @@ -4086,9 +4086,12 @@ expand_sdiv_pow2 (scalar_int_mode mode, rtx op0, HOST_WIDE_INT d)
>      {
>        temp = gen_reg_rtx (mode);
>        temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, 1);
> -      temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
> -			   0, OPTAB_LIB_WIDEN);
> -      return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
> +      if (temp != NULL_RTX)
> +	{
> +	  temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
> +			       0, OPTAB_LIB_WIDEN);
> +	  return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
> +	}
>      }
>  
>    if (HAVE_conditional_move
> @@ -4122,17 +4125,20 @@ expand_sdiv_pow2 (scalar_int_mode mode, rtx op0, HOST_WIDE_INT d)
>  
>        temp = gen_reg_rtx (mode);
>        temp = emit_store_flag (temp, LT, op0, const0_rtx, mode, 0, -1);
> -      if (GET_MODE_BITSIZE (mode) >= BITS_PER_WORD
> -	  || shift_cost (optimize_insn_for_speed_p (), mode, ushift)
> -	     > COSTS_N_INSNS (1))
> -	temp = expand_binop (mode, and_optab, temp, gen_int_mode (d - 1, mode),
> -			     NULL_RTX, 0, OPTAB_LIB_WIDEN);
> -      else
> -	temp = expand_shift (RSHIFT_EXPR, mode, temp,
> -			     ushift, NULL_RTX, 1);
> -      temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
> -			   0, OPTAB_LIB_WIDEN);
> -      return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
> +      if (temp != NULL_RTX)
> +	{
> +	  if (GET_MODE_BITSIZE (mode) >= BITS_PER_WORD
> +	      || shift_cost (optimize_insn_for_speed_p (), mode, ushift)
> +	      > COSTS_N_INSNS (1))
> +	    temp = expand_binop (mode, and_optab, temp, gen_int_mode (d - 1, mode),

Long line.

OK otherwise, thanks.  I guess these failed attempts will leave
a few unused temporary registers around (from the gen_reg_rtxes)
but it's going to be hard to avoid that in a clean way.

Richard

> +				 NULL_RTX, 0, OPTAB_LIB_WIDEN);
> +	  else
> +	    temp = expand_shift (RSHIFT_EXPR, mode, temp,
> +				 ushift, NULL_RTX, 1);
> +	  temp = expand_binop (mode, add_optab, temp, op0, NULL_RTX,
> +			       0, OPTAB_LIB_WIDEN);
> +	  return expand_shift (RSHIFT_EXPR, mode, temp, logd, NULL_RTX, 0);
> +	}
>      }
>  
>    label = gen_label_rtx ();