Re: [PATCH] Restrict the two sources of vect_recog_cond_expr_convert_pattern to be of the same type when convert is extension.

[Jakub Jelinek <jakub@redhat.com>]

On Wed, Feb 16, 2022 at 05:03:09PM +0800, liuhongt via Gcc-patches wrote:
> > > +(match (cond_expr_convert_p @0 @2 @3 @6)
> > > + (cond (simple_comparison@6 @0 @1) (convert@4 @2) (convert@5 @3))
> > > +  (if (types_match (TREE_TYPE (@2), TREE_TYPE (@3))
> >
> > But in principle @2 or @3 could safely differ in sign, you'd then need to ensure
> > to insert sign conversions to @2/@3 to the signedness of @4/@5.
> >
> It turns out differ in sign is not suitable for extension(but ok for truncation),
> because it's zero_extend vs sign_extend.
> 
> The patch add types_match check when convert is extension.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
> And native Bootstrapped and regtested on CLX.
> 
> Ok for trunk?
> 
> gcc/ChangeLog:
> 
> 	PR tree-optimization/104551
> 	PR tree-optimization/103771
> 	* match.pd (cond_expr_convert_p): Add types_match check when
> 	convert is extension.
> 	* tree-vect-patterns.cc
> 	(gimple_cond_expr_convert_p): Adjust comments.
> 	(vect_recog_cond_expr_convert_pattern): Ditto.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.target/i386/pr104551.c: New test.
> ---
>  gcc/match.pd                             |  8 +++++---
>  gcc/testsuite/gcc.target/i386/pr104551.c | 24 ++++++++++++++++++++++++
>  gcc/tree-vect-patterns.cc                |  6 ++++--
>  3 files changed, 33 insertions(+), 5 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr104551.c
> 
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 05a10ab6bfd..8e80b9f1576 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -7692,11 +7692,13 @@ and,
>    (if (INTEGRAL_TYPE_P (type)
>         && INTEGRAL_TYPE_P (TREE_TYPE (@2))
>         && INTEGRAL_TYPE_P (TREE_TYPE (@0))
> -       && INTEGRAL_TYPE_P (TREE_TYPE (@3))
>         && TYPE_PRECISION (type) != TYPE_PRECISION (TREE_TYPE (@0))
>         && TYPE_PRECISION (TREE_TYPE (@0))
>  	  == TYPE_PRECISION (TREE_TYPE (@2))
> -       && TYPE_PRECISION (TREE_TYPE (@0))
> -	  == TYPE_PRECISION (TREE_TYPE (@3))
> +       && (types_match (TREE_TYPE (@2), TREE_TYPE (@3))
> +	   || ((TYPE_PRECISION (TREE_TYPE (@0))
> +		== TYPE_PRECISION (TREE_TYPE (@3)))
> +	       && INTEGRAL_TYPE_P (TREE_TYPE (@3))
> +	       && TYPE_PRECISION (TREE_TYPE (@3)) > TYPE_PRECISION (type)))
>         && single_use (@4)
>         && single_use (@5))))

I find this quite unreadable, it looks like if @2 and @3 are treated
differently.  I think keeping the old 3 lines and just adding
      && (TYPE_PRECISION (TREE_TYPE (@0)) >= TYPE_PRECISION (type)
	  || (TYPE_UNSIGNED (TREE_TYPE (@2))
	      == TYPE_UNSIGNED (TREE_TYPE (@3))))
after it ideally with a comment why would be better.
Note, if the precision of @0 and type is the same, I think signedness can
still differ, no?

	Jakub