On Thu, 2022-12-22 17:42:16 +0000, Andrew Carlotti via Gcc-patches <gcc-patches@gcc.gnu.org> wrote:
> New patch below, bootstrapped and regression tested on
> aarch64-unknown-linux-gnu and x86_64-pc-linux-gnu - ok to merge?

> diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
> index fece876099c1687569d6351e7d2416ea6acae5b5..ce2441f2a6dbdf2d8fe42755d5d1abd8a631bb5c 100644
> --- a/gcc/tree-ssa-loop-niter.cc
> +++ b/gcc/tree-ssa-loop-niter.cc
> @@ -42,6 +42,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "tree-chrec.h"
>  #include "tree-scalar-evolution.h"
>  #include "tree-dfa.h"
> +#include "internal-fn.h"
>  #include "gimple-range.h"
>  
>  
> @@ -2198,6 +2199,224 @@ number_of_iterations_popcount (loop_p loop, edge exit,
>    return true;
>  }
>  
> +/* Return an expression that counts the leading/trailing zeroes of src.
> +
> +   If define_at_zero is true, then the built expression will be defined to
> +   return the precision of src when src == 0 (using either a conditional
> +   expression or a suitable internal function).
> +   Otherwise, we can elide the conditional expression and let src = 0 invoke
> +   undefined behaviour.  */
> +
> +static tree
> +build_cltz_expr (tree src, bool leading, bool define_at_zero)
> +{
[...]
> +
> +  tree call;
> +  if (use_ifn)
> +    {
> +      call = build_call_expr_internal_loc (UNKNOWN_LOCATION, ifn,
> +					   integer_type_node, 1, src);
> +      int val;
> +      scalar_int_mode mode = SCALAR_INT_TYPE_MODE (utype);
         ^^^^^^^^^^^^^^^^^^^^

This will give us a new unused variable warning.

> +      int optab_defined_at_zero
> +	= leading ? CLZ_DEFINED_VALUE_AT_ZERO (mode, val)
> +		  : CTZ_DEFINED_VALUE_AT_ZERO (mode, val);
> +      if (define_at_zero && !(optab_defined_at_zero == 2 && val == prec))
> +	{
> +	  tree is_zero = fold_build2 (NE_EXPR, boolean_type_node, src,
> +				      build_zero_cst (TREE_TYPE (src)));
> +	  call = fold_build3(COND_EXPR, integer_type_node, is_zero, call,
> +			     build_int_cst (integer_type_node, prec));
> +	}
> +    }

MfG, JBG

--