[PATCH/AARCH64] Fix 64893: ICE with vget_lane_u32 with C++ front-end at -O0

[Jakub Jelinek]

On Mon, Feb 02, 2015 at 02:51:43PM -0800, Andrew Pinski wrote:
> While trying to build the GCC 5 with GCC 5, I ran into an ICE when
> building libcpp at -O0.  The problem is the C++ front-end was not
> folding sizeof(a)/sizeof(a[0]) when passed to a function at -O0. The
> C++ front-end keeps around sizeof until the gimplifier and there is no
> way to fold the expressions that involve them.  So to work around the
> issue we need to change __builtin_aarch64_im_lane_boundsi to accept an
> extra argument and change the first two arguments to size_t type so we
> don't get an extra cast there and do the division inside the compiler
> itself.

Relying on anything being folded at -O0 when the language does not guarantee
it is going to be more and more of a problem.  So I think your patch is
reasonable (of course, I'll defer this to target maintainers).

> +      rtx totalsize = expand_normal (CALL_EXPR_ARG (exp, 0));
> +      rtx elementsize = expand_normal (CALL_EXPR_ARG (exp, 1));
> +      if (CONST_INT_P (totalsize) && CONST_INT_P (elementsize))
> +	{
> +	  rtx lane_idx = expand_normal (CALL_EXPR_ARG (exp, 2));
> +          if (CONST_INT_P (lane_idx))
> +	    aarch64_simd_lane_bounds (lane_idx, 0, UINTVAL (totalsize)/UINTVAL (elementsize), exp);

Too long line?  Also, missing spaces around / .  And, ICE if
somebody uses __builtin_aarch64_im_lane_boundsi (4, 0, 0);
So you need to check and complain for zero elementsize too.

> +          else
> +	    error ("%Klane index must be a constant immediate", exp);
> +	}
>        else
> -	error ("%Klane index must be a constant immediate", exp);
> +	sorry ("%Ktotal size and element size must be a constant immediate", exp);

But why sorry?  If you say the builtin requires constant arguments, then it
is not sorry, but error, it is not an unimplemented feature.

	Jakub