Ilya Leoshkevich <[email protected]> writes:
> z13 supports only non-signaling vector comparisons. This means we
> cannot vectorize LT, LE, GT, GE and LTGT when compiling for z13.
> However, we cannot express this restriction today: the code only checks
> whether vcond$a$b optab, which does not contain information about the
> operation.
>
> Introduce a hook that tells whether target supports certain vector
> comparison operations with certain modes.
>
> gcc/ChangeLog:
>
> 2019-08-09 Ilya Leoshkevich <[email protected]>
>
> * doc/tm.texi (TARGET_VCOND_SUPPORTED_P): Document.
> * doc/tm.texi.in (TARGET_VCOND_SUPPORTED_P): Document.
> * optabs-tree.c (expand_vec_cond_expr_p): Use vcond_supported_p
> in addition to get_vcond_icode.
> * target.def (vcond_supported_p): New hook.
> * targhooks.c (default_vcond_supported_p): Likewise.
> * targhooks.h (default_vcond_supported_p): Likewise.
IMO it'd be cleaner to have a new optabs-query.[hc] helper that uses
the predicate for operand 3 to test whether a particular comparison
is supported. I guess this would require a cached rtx to avoid
generating too much garbage rtl though (via GTY((cache))).
If the general feeling is that we should have a hook instead, I assume
the same restrictions would apply to the vec_cmp@var{m}@var{n} optab too,
on targets that use that. It might be worth generalising the hook so
that it applies to both patterns.
> diff --git a/gcc/target.def b/gcc/target.def
> index b2332d8215c..4cd2a964c0e 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -3379,6 +3379,17 @@ the vector element type.",
> HOST_WIDE_INT, (const_tree type),
> default_vector_alignment)
>
> +DEFHOOK
> +(vcond_supported_p,
> + "Define this to restrict which vector comparison operations are supported
> by\n\
> +vcond$a$b expander. An operation is represented by its operand machine
> mode\n\
Maybe s/vcond$a$b expander/a @code{vcond@var{m}@var{n}} instruction pattern/
for consistency with the .md documentation.
> +@code{OP_MODE}, its result machine mode @code{RESULT_MODE} and @code{enum\n\
> +tree_code CODE}. The main use of this hook is to support machines which\n\
> +provide only certain vector comparison instructions, e.g. only
> non-signaling\n\
> +ones. The default is that all operations are supported.",
...if the associated pattern exists.
> + bool, (machine_mode result_mode, machine_mode op_mode, int code),
> + default_vcond_supported_p)
> +
> DEFHOOK
> (array_mode,
> "Return the mode that GCC should use for an array that has\n\
> diff --git a/gcc/targhooks.c b/gcc/targhooks.c
> index 1d12ec54704..2b9a5d12bab 100644
> --- a/gcc/targhooks.c
> +++ b/gcc/targhooks.c
> @@ -448,6 +448,18 @@ default_scalar_mode_supported_p (scalar_mode mode)
> }
> }
>
> +/* Return true if vcond$a$b expander supports vector comparisons using the
> CODE
> + of type enum tree_code, in which the operands have machine mode OP_MODE
> and
> + the result has machine mode RESULT_MODE. */
> +
> +bool
> +default_vcond_supported_p (machine_mode result_mode ATTRIBUTE_UNUSED,
> + machine_mode op_mode ATTRIBUTE_UNUSED,
> + int code ATTRIBUTE_UNUSED)
No need to repeat the documentation here -- just say which hook it's
the default for.
Thanks,
Richard
